Biomedical subjects

G R Breese

Publications and source records attributed to G R Breese.

At least 37 records · Page 2Linked to original sources

PubMed1998

Action of ethanol and zolpidem on gamma-aminobutyric acid responses from cerebellar Purkinje neurons: relationship to beta-adrenergic receptor input.

The observation that cerebellar Purkinje cells contain type-I benzodiazepine-sensitive GABA(A) receptors is consistent with findings in the present work that the majority of Purkinje neurons are sensitive to enhancement of GABA by the type-1 benzodiazepine agonist, zolpidem. Previous work has demonstrated a relation between zolpidem and ethanol enhancement of GABA responses in several brain regions, but had not tested Purkinje neurons. Therefore, given that a majority of Purkinje neurons were found to be sensitive to zolpidem, ethanol would have been expected to enhance GABA responses from this cell type. However, in agreement with earlier electrophysiological studies, ethanol enhanced GABA inhibitory responses from only a small proportion of these cerebellar Purkinje neurons. Rather than enhancement of GABA, local application of ethanol either inhibited or did not affect responses to GABA from a majority of cerebellar-Purkinje neurons. Nonetheless, as previously reported, a portion of the Purkinje neurons initially insensitive to ethanol enhancement of GABA became sensitive to this action of ethanol with co-application of the beta-adrenergic agonist, isoproterenol. Thus, these results collectively implicate a beta-adrenergic input dependency for ethanol enhancement of GABA from some, but not all, cerebellar Purkinje neurons sensitive to zolpidem. Because a beta-adrenergic input did not allow ethanol enhancement of GABA from all Purkinje neurons, future studies should explore the possibility that other auxiliary neural inputs to zolpidem-sensitive cerebellar Purkinje neurons may be required for ethanol enhancement of GABA responsiveness when a beta-adrenergic input does not have this action. Likewise, knowing that the action of zolpidem can predict ethanol enhancement of GABA in other brain regions, the present findings suggest that a future determination be made concerning whether zolpidem-sensitive neurons in these other regions of brain require a beta-adrenergic or an alternative neural input for ethanol enhancement of GABA responses.

Adrenergic beta-Agonists↗

PubMed1997

Adeno-associated virus (AAV) vector antisense gene transfer in vivo decreases GABA(A) alpha1 containing receptors and increases inferior collicular seizure sensitivity.

In the inferior colliculus, adeno-associated virus (AAV) vectors are capable of gene transfer and stable, long-term expression, but it remained to be shown if this in vivo gene transfer could alter focal seizure sensitivity in the inferior colliculus. Because GABA receptors directly modulate inferior collicular seizures, AAV vectors were constructed with a cytomegalovirus (CMV) promoter and a truncated, human GABA(A) alpha1 cDNA in both the sense and antisense orientations. Seven days after collicular microinjection of the sense vectors (1 microl; 3 x 10(9) particles/microl), neurons exhibited GABA(A) alpha-like immunoreactivity in amounts far exceeding endogenous concentrations. Unilateral or bilateral sense vector infusion had no effect on inferior collicular seizure parameters or on [3H]zolpidem binding. In contrast, bilateral infusion of the antisense AAV-GABA(A) alpha1 vector (1 microl; 3 x 10(8) particles/microl) caused a 137% increase in the seizure duration. Moreover, unilateral antisense vector infusion produced a localized, 48% decrease in [3H]zolpidem binding. Thus, in the inferior colliculus, antisense AAV-CMV vectors can reduce a specific receptor subunit protein and change receptor function that directly influences in vivo seizure sensitivity.

Animals↗

PubMed1997

Flumazenil blockade of anxiety following ethanol withdrawal in rats.

In previous research, the drug flumazenil has been categorized both as a pure benzodiazepine antagonist and as a benzodiazepine partial agonist. The following studies used an elevated plus maze to test whether flumazenil would exert any antianxiety action in rats. While chlordiazepoxide (3.0 mg/kg), ethanol (0.75 g/kg), and the atypical benzodiazepine zolpidem (1.0 mg/kg) all significantly increased time spent on the open arms and percent open arm entries, flumazenil (1-10 mg/kg) alone did not produce any anxiolytic effects on the maze. Withdrawal from chronic ethanol treatment led to a decrease in open arm time and percent open arm entries. Flumazenil (3.0 mg/kg) blocked these changes, suggesting that the effects of flumaxenil are at least partially dependent upon the levels of stress or anxiety in the subjects. An anxiolytic action of flumazenil was not seen following the central administration of the neuropeptide corticotropin-releasing factor (CRF), which reduced open arm time on the elevated plus maze. These results support the hypothesis that the mechanism of action for flumazenil effects on the anxiety observed during ethanol withdrawal involves antagonism of an endogenous benzodiazepine inverse agonist, rather than activity as a partial agonist or blockade of CRF-mediated effects.

Animals↗

PubMed1997

Differential effects of bilateral dopamine depletion in neonatal and adult rats.

Both Lesch-Nyhan syndrome and Parkinson's disease are associated with decreased brain dopamine, yet each disorder is characterized by a different set of motor symptoms. Lesch-Nyhan syndrome is manifested in early childhood, while parkinsonism usually does not appear until adulthood, suggesting that age at the time of dopamine loss is one determinant of the effects of neurotransmitter deficiency. Support for this view is found in studies of animals given dopamine-depleting lesions at different ages and then tested in adulthood. Animals lesioned as neonates show a supersensitivity to dopamine agonists, especially D1-dopamine receptor agonists, and to MK-801, an NMDA receptor antagonist. In addition, neonatally treated animals show a 'priming' effect following repeated exposure to D1-dopamine agonists. Animals depleted of dopamine as adults are more supersensitive to agonists acting on the D2-dopamine receptor, and do not evidence priming to dopamine agonists or an enhanced response to MK-801. These differential pharmacological profiles suggest that the changes in neurotransmitter systems following dopamine depletion are, at least in part, determined by age at the time of the lesion.

Adult↗

PubMed1997

Ultrasonic vocalization behavior differs between lines of ethanol-preferring and nonpreferring rats.

To further understand the relationship between emotional state and alcohol intake in rats, the tendency to emit ultrasonic vocalizations in response to an aversive, but nonpainful, air puff stimulus was tested in several rat lines. Included in this group were Maudsley Reactive (MR) and Non-Reactive (MNR) rats, and several lines of rats with either high ethanol preference or a low ethanol preference: Preferring, (P), Alko-Alcohol (AA), and Fawn-Hooded (FH) animals; and Non-Preferring (NP), Alko-Non-Alcohol (ANA), and Flinders Resistant Line (FRL). MR rats emitted fewer ultrasonic vocalizations (USVs) and showed less preference for ethanol than did MNR animals. An overall analysis that included the P, NP, FH, FRL, AA, and ANA groups demonstrated a significant negative correlation between the total number of USVs emitted and ethanol consumption. NP, FRL, and especially ANA rats (low ethanol-preferring) emitted the most USVs--to an extent similar to that typically found for normal rats. The duration of vocalizing was higher only in the NP and the FRL rats the relative to their P and FH comparison groups, respectively. In the ethanol-preferring and nonpreferring lines, the numbers of USVs emitted correlated positively with the duration of vocalizing, but not with the latency to vocalize, which in turn did not correlate strongly with ethanol intake. The latency to vocalize did not correlate significantly with ethanol intake across all drinking lines or MR or MNR rats, but was found to be higher in FH and AA rats relative to their nondrinking comparison groups. These associations suggest that the relationship between emotional state and ethanol drinking is complex and cannot be attributed to a simple elevated state of anxiety or emotionality. Further examination of the central nervous system mechanisms mediating the difference in USVs between paired lines of ethanol-preferring and nonpreferring rats may identify neurochemical factors that predict ethanol preference.

Alcohol Drinking↗

PubMed1996

Dopamine transporters are markedly reduced in Lesch-Nyhan disease in vivo.

Dopamine (DA) deficiency has been implicated in Lesch-Nyhan disease (LND), a genetic disorder that is characterized by hyperuricemia, choreoathetosis, dystonia, and compulsive self-injury. To establish that DA deficiency is present in LND, the ligand WIN-35,428, which binds to DA transporters, was used to estimate the density of DA-containing neurons in the caudate and putamen of six patients with classic LND. Comparisons were made with 10 control subjects and 3 patients with Rett syndrome. Three methods were used to quantify the binding of the DA transporter so that its density could be estimated by a single dynamic positron emission tomography study. These approaches included the caudate- or putamen-to-cerebellum ratio of ligand at 80-90 min postinjection, kinetic analysis of the binding potential [Bmax/(Kd x Vd)] using the assumption of equal partition coefficients in the striatum and the cerebellum, and graphical analysis of the binding potential. Depending on the method of analysis, a 50-63% reduction of the binding to DA transporters in the caudate, and a 64-75% reduction in the putamen of the LND patients was observed compared to the normal control group. When LND patients were compared to Rett syndrome patients, similar reductions were found in the caudate (53-61%) and putamen (67-72%) in LND patients. Transporter binding in Rett syndrome patients was not significantly different from the normal controls. Finally, volumetric magnetic resonance imaging studies detected a 30% reduction in the caudate volume of LND patients. To ensure that a reduction in the caudate volume would not confound the results, a rigorous partial volume correction of the caudate time activity curve was performed. This correction resulted in an even greater decrease in the caudate-cerebellar ratio in LND patients when contrasted to controls. To our knowledge, these findings provide the first in vivo documentation of a dopaminergic reduction in LND and illustrate the role of positron emission tomography imaging in investigating neurodevelopmental disorders.

Adolescent↗

PubMed1996

Neuroanatomical characterization of Fos induction in rat behavioral models of anxiety.

Immunohistochemical staining for Fos-like immunoreactivity (Fos-LI) was used to map functional activation in discrete brain regions of rats processed in three empirical models of anxiety: foot shock avoidance responding in a shuttle box, the elevated plus maze, and an air puff-induced ultrasonic vocalization test. The avoidance test and elevated plus maze induced prominent Fos-LI in select brain regions, including the medial prefrontal, cingulate, and ventrolateral orbital cortices, taenia tecta, nucleus accumbens, paraventricular nucleus of the hypothalamus, medial nucleus of the amygdala and lateral septum. Air puff stimuli that produced ultrasonic vocalizations induced Fos-LI to a more limited extent compared to the plus maze and avoidance test, with only the medial prefrontal cortex, medial nucleus of the amygdala, and lateral septum being significantly affected by air-puff. Even though the sensory stimuli and environmental conditions associated with the three anxiety models were markedly different, specific common forebrain regions were affected, i.e. the medial prefrontal cortex, medial amygdala, and lateral septum. It is hypothesized that these regions are components of a circuit in the rat brain related to anxiety or distress. To determine the potential relationship between generalized arousal and the observed induction of Fos-LI in the anxiety models, rats were tested in a non-aversive situation involving marked behavioral activation. Accordingly, after vigorous bar pressing behavior for reinforcement with sweetened condensed milk, induction of Fos-LI was minimal and comparable to that in unhandled control rats. These latter data indicate that the distinctive neuroanatomical patterns of Fos-LI observed in the paradigms related to anxiety were not simply due to generalized behavioral activation. In summary, select common brain regions were identified that express Fos-LI in empirical models of anxiety. These data provide a functional framework to explore neuroanatomical sites of action of psychotherapeutic drugs that influence behavioral responses in these tasks.

Animals↗

PubMed1996

Differential and persistent expression patterns of CNS gene transfer by an adeno-associated virus (AAV) vector.

Safe, long-term gene expression is a primary criteria for effective gene therapy in the brain, so studies were initiated to evaluate adeno-associated virus (AAV) vector transfer of a reporter gene into specific sites of the rat brain. In the 4 day old rat, site infusions of AAV-CMV-lacZ (1 microliter; 5 x 10(4) particles) produced neuronal beta-galactosidase gene expression 3 weeks later in the hippocampus and inferior colliculus, but not in the cerebral cortex. Seven days after infusion of AAV-CMV-lacZ viral vectors (1 microliter) in the adult rat, beta-galactosidase gene expression was found in the olfactory tubercle, caudate, hippocampus, piriform cortex and inferior colliculus. primarily in multipolar neurons close to the infusion site. Three months after vector microinfusion, similar levels of gene expression remained in the olfactory tubercle and the inferior colliculus, with some reduction found in the caudate, but substantial reductions in beta-galactosidase gene expression occurred in the hippocampus and piriform cortex. In no case were obvious signs of toxicity noted. Therefore, AAV vectors can transfer foreign genes into the adult and neonatal CNS, but the pattern and longevity of gene expression depends upon the area of brain being studied.

Animals↗

PubMed1996

Functional classification of antidepressants based on antagonism of swim stress-induced fos-like immunoreactivity.

Autoradiographic analysis of 14C-2-deoxyglucose (2-DG) uptake and immunocytochemical assessment of Fos-like immunoreactivity (Fos-LI) were used to assess swim stress-induced changes in metabolic activity in brain and to define the effect of chronic treatment with antidepressants from different pharmacological classes. Saline-treated rats processed in the forced swim test exhibited marked increases in Fos-LI in limbic cortical regions, lateral septum, medial amygdala and paraventricular nucleus of the hypothalamus (PVN). Uptake of 2-DG was increased by swim stress in some of the same brain regions where Fos-LI was induced, with the notable exception of a lack of a change in the PVN. Rats received injections for 3 wk with imipramine, desipramine, fluoxetine, nisoxetine, tranylcypromine or mianserin before being processed in the forced swim test. Chronic treatment with imipramine and desipramine alone induced Fos-LI in the central nucleus of the amygdala and the dorsolateral bed nucleus of the stria terminalis. After tranylcypromine treatment, Fos-LI was induced in many brain regions including limbic cortex, amygdala and paraventricular nucleus of the hypothalamus. None of the other antidepressants induced Fos-LI in any brain region examined. Chronic administration of imipramine, desipramine and nisoxetine antagonized the swim induced expression of Fos-LI in the PVN and in limbic cortical regions, including the medial prefrontal ventrolateral orbital and cingulate cortices. Chronic treatment with fluoxetine, tranylcypromine and mianserin did not alter swim stress-induced Fos-LI in any brain region. Thus, only antidepressant drugs that affect norepinephrine uptake (i.e., imipramine, desipramine and nisoxetine) antagonized swim stress-induced Fos-LI. In contrast to the action of chronic imipramine on Fos-LI induced by swim, chronic administration of imipramine did not antagonize the stress-induced changes in 2-DG uptake in limbic cortical regions. Acute administration of propranolol, which blocks beta-adrenergic receptors, reduced the number of cells staining for Fos-LI in limbic cortical regions, resembling the effects produced by chronic imipramine, desipramine and nisoxetine. In the PVN, neither propranolol nor prazosin (an alpha 1 antagonist) blocked the swim-induced Fos-LI, suggesting that swim-induced Fos-LI in the PVN is not under control of beta- or alpha 1-adrenergic receptors. These latter results imply that adaptation of noradrenergic receptors by chronic imipramine may not be related to the antagonism of stress-induced Fos-LI. The clear functional differences of the various antidepressant agents on swim stress-induced Fos-LI after chronic administration provide a functional classification of antidepressant drug action not previously identified.

Animals↗

PubMed1996

Nicotine-induced inhibition in medial septum involves activation of presynaptic nicotinic cholinergic receptors on gamma-aminobutyric acid-containing neurons.

Neuronal responses to drugs acting on nicotinic cholinergic receptors (nAChRs) were examined in the rat medial septal area by using an in vivo extracellular single-unit recording technique. In the medial septal area, iontophorectically applied nicotine inhibited neuronal activity in 45% of the neurons, but had no effect on the remaining neurons. Dihydro-beta-erythroidine application to neurons in the medial septal area not only blocked nicotine-induced inhibition, but also reduced spontaneous neuronal activity of the neurons. When Mg++ was applied iontophoretically to block presynaptic neurotransmitter release, a significant reduction in spontaneous neural activity also was observed. No further reduction of spontaneous activity by dihydro-beta-erythroidine occurred in the presence of Mg++, suggesting an apparent tonic excitatory input to the majority of neurons in the medial septal area under the control of presynaptic nAChRs. Mg++ abolished the nicotine-induced inhibition in the medial septal area without having an effect on nicotine-induced inhibition in the cerebellum. Thus, these data provide evidence that the inhibitory effects of nicotine in the medial septum are due to an action on presynaptic nAChRs, controlling the release of an inhibitory neurotransmitter. Of the medial septal neurons which showed no response to nicotine, nicotine produced excitation in 21% of the cells after Mg++ application, indicating that nicotine can have a direct action on postsynaptic nAChRs, in addition to its presynaptic action, in the medial septum. Finally, application of the gamma-aminobutyric acid antagonist bicuculline reduced the nicotine-induced inhibition on the majority of medial septal neurons tested, but was without effect on the inhibition produced by nicotine on cerebellar Purkinje neurons. Consequently, it can be concluded that the nicotine-induced inhibition in the medial septum is the result of gamma-aminobutyric acid release due to its action on presynaptic nAChRs present on gamma-aminobutyric acid-containing terminals.

Animals↗

PubMed1996

Evidence for a selective effect of ethanol on N-methyl-d-aspartate responses: ethanol affects a subtype of the ifenprodil-sensitive N-methyl-d-aspartate receptors.

An extracellular electrophysiological approach was used to determine the effect of ethanol on responses to N-methyl-D-aspartate (NMDA) across several brain regions in urethane-anesthetized rats. The results indicated that, in most brain regions, ethanol inhibited the NMDA-induced increases in firing rate for some, but not all, spontaneously active neurons. Ethanol functioned as an NMDA antagonist for some neurons in the medial septum, red nucleus, deep mesencephalic nucleus, substantia nigra reticulata, ventral tegmental area and cerebellum. In the hippocampus, ethanol inhibited NMDA responses from all neurons. However, ethanol was not found to be active against NMDA responses in the lateral septum, suggesting that there is a degree of regional specificity for ethanol inhibition of NMDA responses. It was then established in unanesthetized rats that ethanol also antagonized responses to NMDA in some, but not all, neurons in the medial septum and cortex, indicating that the differential action of ethanol on NMDA responses obtained in the urethane-anesthetized rats was not due to the anesthetic. Based on an earlier study showing that the effects of ifenprodil and ethanol on NMDA responses were correlated, the ability of ethanol to inhibit NMDA responses was compared with changes produced by ifenprodil on the same neurons, where ethanol did or did not affect NMDA responses. In the several brain regions investigated, ethanol inhibited NMDA responses in a subgroup of neurons in which ifenprodil inhibited NMDA-induced increases in firing. For all neurons investigated, if a cell was insensitive to ifenprodil antagonism of NMDA responses then ethanol also was ineffective against the response to NMDA. These results suggest that ethanol acts on an ifenprodil-sensitive NMDA receptor subtype. Given that previous investigations have suggested that the NMDA receptor type 2B subunit is essential for the action of ifenprodil, the positive relationship between the actions of ifenprodil and ethanol on responses to NMDA is consistent with the hypothesis that the combination of specific receptor subunits forming an NMDA receptor on a neuron determines the ability of ethanol to antagonize an NMDA response.

Animals↗

PubMed1995

Metabolic and functional mapping of the neural network subserving inferior collicular seizure generalization.

The sensory-motor portion of the inferior collicular cortex is capable of seizure genesis that is characterized initially by coincident wild running behaviors and localized electrographic afterdischarge. With repeated stimulations, this seizure activity spreads into the forebrain, producing generalized tonic-clonic or myoclonic seizure activity. In order to characterize the neural network subserving this caudal-rostral seizure generalization, three mapping techniques were used: 2-deoxyglucose (2-DG) utilization, c-fos expression and local anesthetic microinjection. Kindled seizure generalization from the inferior collicular cortex produced a global increase in 2-DG accumulation, while relative 2-DG increases were found in the inferior collicular cortex, dorsal lateral lemniscus, dorsal central gray, peripeduncular nucleus, medial geniculate nucleus, substantia nigra, entopeduncular nucleus, ventroposterior and centromedian thalamus and tenia tectum, as well as the perirhinal, somatosensory and frontal cortices. Kindled seizure generalization also increased c-fos-like immunoreactivity (FLI) in the inferior collicular cortex, cuneiform nucleus, dorsal lateral nucleus of the lateral lemniscus, peripeduncular nucleus, caudal central gray, dentate gyrus of the hippocampus, rhinal fissure area of the perirhinal cortex and the frontal cortex. Microinjections of procaine into the amygdala, perirhinal cortex, entopeduncular nucleus, substantia nigra, peripeduncular nucleus, dorsal central gray, and pontine reticular nucleus all prevented generalized seizure behaviors, but had no effect on the wild running seizures. Conversely, procaine microinjection into the area of the cuneiform nucleus/pedunculopontine tegmental nucleus prevented the wild running seizure but did not block the generalized seizure activity. Neither wild running, nor generalized seizures were altered following procaine microinjections into the anterior thalamus, sub-thalamus, lateral hypothalamus, hippocampus or deep superior colliculus. Thus, specific forebrain sites form a widespread neural network that mediates the generalization of seizure activity from the inferior collicular cortex into the forebrain.

Animals↗

PubMed1995

Preparative methods for brain slices: a discussion.

Criteria for slice health and factors that affect slice health were discussed by many of the participants in the conference. In addition to the standard parameters of slice health (energy metabolism, morphology, electrophysiological responsiveness) more subtle but possibly equally important manifestations of slice health were discussed. These included protein synthesis, and more subtle changes, of which we are becoming increasingly aware. The latter include synthesis of stress-related proteins, altered levels of phosphorylation, altered levels of proteolysis. These last were only touched on, but it is becoming apparent they do in fact constitute important manifestations of differences between the slice preparation and the in vivo tissue. They may well lead to quite different responses in slices from those that occur in vivo. While many ways of optimizing slice wellness were discussed, there was a fair consensus that certain adjustments will optimize the most widely measured aspects of cell function. These include the following, wherever possible. Use of young animals, use of the interface chamber, preparing slices with the vibratome, pre-treating animals with ice-cold cardiac perfusion before sacrificing, using pre-incubation media which reduce NMDA receptor activation, free radical formation and cell swelling. When possible these treatments should perhaps be continued into the normal incubation. This being said, many viewpoints were actually expressed in the discussion, and it should be read to get a feel for the usefulness of the different approaches.

Animals↗

PubMed1995

Distribution of [3H]zolpidem binding sites in relation to messenger RNA encoding the alpha 1, beta 2 and gamma 2 subunits of GABAA receptors in rat brain.

Localization of the messenger RNAs that encode the alpha 1, beta 2 and gamma 2 subunits of GABAA showed a distinct topographic pattern in rat brain which corresponded with [3H]zolpidem binding in most brain regions. The close topographic correspondence between the specific receptor subunits examined and the distribution of [3H]zolpidem binding sites provides support for the hypothesis that this benzodiazepine type 1 selective ligand binds to a GABAA receptor that consists of alpha 1, beta 2 and gamma 2 subunits in the rat brain. Brain regions with relatively high densities of alpha 1, beta 2 and gamma 2 subunits of GABAA and [3H]zolpidem binding included olfactory bulb, medial septum, ventral pallidum, diagonal band, inferior colliculus, substantia nigra pars reticulata and specific layers of the cortex. Two areas with low [3H]zolpidem binding and a virtual absence of these GABAA receptor subunit messenger RNAs were the lateral septum and the striatum. In contrast to the discrete pattern observed for alpha 1 and beta 2 subunit messenger RNAs, the gamma 2 subunit messenger RNA was distributed more diffusely in brain. Only the hippocampus, layer 2 of the piriform cortex and the cerebellum showed a strong concentration of the gamma 2 subunit messenger RNA. It was determined with a polymerase chain reaction assay that both long and short variants of the gamma 2 subunit messenger RNAs were present within several of the brain sites selected for examination. Sites with high densities of [3H]zolpidem binding sites had a greater relative abundance of the gamma 2 long splice variant, compared to the gamma 2 short variant. There were some regions that expressed high levels of alpha 1, beta 2 and gamma 2S subunit messenger RNAs but low [3H]zolpidem binding, suggesting that gamma 2 splice variant expression may modulate high-affinity [3H]zolpidem binding. To determine relationships between in vitro [3H]zolpidem binding and functional sensitivity in vivo, interactions between zolpidem and GABA were assessed in brain regions that contained high and low densities of [3H]zolpidem binding sites. In the medial septum, a brain region with a high concentration of [3H]zolpidem binding sites, iontophoretic application of zolpidem enhanced the inhibitory effect of GABA responses on 70% of the neurons examined. In the lateral septum, which contains very low densities of [3H]zolpidem binding sites, neurons were not sensitive to zolpidem enhancement of GABA-induced inhibition. These electrophysiological results demonstrate a correspondence between the regional distribution of [3H]zolpidem binding in vitro and functional sensitivity to the drug in vivo.

Animals↗

PubMed1995

Regional differences in the effects of chronic ethanol administration on [3H]zolpidem binding in rat brain.

A strong association has been observed between [3H]zolpidem binding and the presence of gamma-aminobutyric acid (GABAA) receptor mRNA for alpha 1-, beta 2-, and gamma 2-subunits in specific brain regions. This correlates with observed sensitivity of individual neurons to zolpidem and ethanol in these same regions. Previous studies using homogenate binding approaches showed small alterations in [3H]zolpidem binding levels after chronic ethanol exposure. This study was undertaken to ascertain if there is regional specificity of the effects of chronic ethanol administration on [3H]zolpidem binding levels. Chronic ethanol administration induced small, but significant alterations in [3H]zolpidem (5 nM) binding in the inferior colliculus, substantia nigra, and the medial septum. [3H]Zolpidem binding was increased in the inferior colliculus and substantia nigra, and decreased in the medial septum. No significant differences in [3H]zolpidem binding were noted in any other brain area analyzed, including the cortex and cerebellum. These findings show that chronic ethanol administration has small effects on [3H]zolpidem binding, although they occur in a site-specific and bidirectional manner. Moreover, there is no correlation between changes in [3H]zolpidem binding and alterations in GABAA receptor subunit expression.

Alcoholism↗

PubMed1995

Effect of zolpidem on gamma-aminobutyric acid (GABA)-induced inhibition predicts the interaction of ethanol with GABA on individual neurons in several rat brain regions.

Previous investigations have suggested a relationship between zolpidem binding within specific brain regions and the ability of ethanol or zolpidem to enhance gamma-aminobutyric acid (GABA)-induced inhibition. The purpose of the present study was to extend our electrophysiological analysis to additional brain sites with high levels of zolpidem binding. In the brain regions chosen, red nucleus and globus pallidus, GABA-induced inhibition was shown to be enhanced by either ethanol or zolpidem on some, but not all, neurons. These findings led to the hypothesis that the effect of zolpidem on GABA-induced inhibition would predict the action of ethanol on responses to GABA for that neuron. When zolpidem and ethanol were applied individually to the same neurons in the red nucleus and globus pallidus, those neurons sensitive to zolpidem enhancement of GABA also were sensitive to ethanol. Conversely, if zolpidem did not enhance responses to GABA, ethanol did not enhance responses to GABA at these brain sites. A similar relationship between the abilities of zolpidem and ethanol to enhance GABA-induced inhibition was obtained in 90% of the neurons studied in the medial septum/diagonal band and ventral pallidum. These studies provide further support for the contention that the zolpidem-sensitive GABAA-benzodiazepine isoreceptor also responds to ethanol. Finally, the expression of GABAA subunit mRNAs was analyzed by polymerase chain reaction from micropunches of several brain regions that contain zolpidem binding sites and exhibit sensitivity to ethanol. Polymerase chain reaction analysis proved more sensitive than in situ hybridization in the detection of receptor subunit mRNAs. Several subunits (alpha 1, alpha 2, alpha 3, beta 2, beta 3 and gamma 2) were common to all brain regions in which ethanol and zolpidem enhanced GABA responses. GABAA receptor alpha 4/5, alpha 6, beta 1, gamma 1, gamma 3 and delta subunits were not consistently expressed in association with the presence of zolpidem binding. These data are consistent with the view that one native GABAA receptor to which zolpidem binds, and on which ethanol acts, contains the GABAA receptor subunits alpha 1, beta 2 and gamma 2; however, the present investigation did not preclude the possibility that other subunit combinations can contribute to ethanol and zolpidem enhancement of responses to GABA.

Animals↗

PubMed1994

Corticotropin-releasing hormone (CRH) antisense oligodeoxynucleotide induces anxiolytic effects in rat.

Antisense oligodeoxynucleotide complementary to the start coding region of rat corticotropin releasing hormone (CRH) mRNA was intracerebroventricularly infused into rats three times at 12-h intervals. In the shuttle-box avoidance procedure antisense-treated rats showed, within 6 h, significant acceleration and increase in the total number of discriminative avoidance responses compared with controls, treated with the corresponding sense probe or vehicle alone. Following the shuttle-box experiment hypothalamic CRH hybridization signals and immunoreactivity were reduced, while CRH immunoreactivity in the median eminence remained unchanged. Plasma ACTH and corticosterone were decreased in antisense-treated animals. It is likely that in addition to a selective blockade of CRH translation, antisense treatment may also interrupt secretion of CRH. Antisense targeting of the hypothalamo-hypophysial-adrenal axis may provide new strategies for the neuropharmacology of affective disorders.

Animals↗

PubMed1994

Altered activity patterns following neonatal 6-hydroxydopamine lesions to dopaminergic neurons: effect of SKF-38393.

The effects of neonatal dopamine depletion on activity levels and locomotor patterns were tested in rats at 4 months of age. Measurements were taken using an activity pattern monitor. The lesioned group was significantly hypoactive in comparison to the control animals during the initial exposures to the monitor. Examination of locomotor paths indicated that the lesioned animals failed to develop the increasingly organized spatial behavior observed in control animals. In a second study, changes in motility and locomotor patterns before, during, and after the repeated administration of a D1-dopamine agonist, SKF-38393 (3.0 mg/kg) were investigated. A priming effect, leading to increases in ambulations and fine movements, was observed only in the lesioned animals after repeated administration of SKF-38393. The D1-dopamine agonist did not change the activity of the unlesioned animals and did not lead to persistent effects in lesioned animals tested 2 and 4 days following the final drug administration. Across the duration of the second study, the lesioned group did not demonstrate hypoactivity. Overall, the experiments showed that neonatal dopamine depletion disrupts the normal patterns of behavior associated with habituation to a novel environment, and repeated administration of SKF-38393 can further alter these abnormal activity patterns.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗