Cytochemical architecture of the entorhinal area.
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Animals↗
Biomedical subjects
C Köhler
Publications and source records attributed to C Köhler.
The selective dopamine D2 receptor antagonist raclopride discriminates between dopamine-mediated motor functions.
The actions on central dopamine (DA) mechanisms of raclopride, a new substituted benzamide, were studied by means of behavioural and biochemical methods in the rat. Raclopride blocked the in vitro binding of the dopamine D2 antagonist 3H-spiperone (IC50 = 32 nM), but not of the unselective D1 antagonist 3H-flupenthixol (IC50 greater than 100,000 nM) in rat striatum, and failed to inhibit striatal DA-sensitive adenylate cyclase in vitro (IC50 greater than 100,000 nM). Raclopride caused a dose-dependent increase in the DA metabolites HVA and DOPAC in the striatum and olfactory tubercle. Behavioural studies showed that raclopride discriminates between the motor behaviours induced by the DA agonist apomorphine. Thus, unlike haloperidol, raclopride blocked apomorphine-induced hyperactivity at considerably lower doses than those inhibiting oral stereotypies. Moreover, raclopride showed a high separation between the doses for blockade of apomorphine-induced hyperactivity and those inducing catalepsy in rats. Raclopride caused a dose-dependent blockade of the specific binding of 3H-spiperone and 3H-N-n-propylnorapomorphine (3H-NPA) in vivo at doses similar to those blocking the behavioural effects of apomorphine. The maximal blockade of 3H-spiperone binding in vivo was lower for raclopride than for haloperidol. Raclopride caused a greater inhibition of 3H-NPA than of 3H-spiperone in vivo binding in the striatum. It is suggested that the ability of raclopride to discriminate between different DA-mediated functions may be attributed to a preferential blockade of a subclass of functionally coupled dopamine D2 receptors in striatal as well as in extrastriatal brain regions in the rat.
Adenylyl Cyclases↗
Dopamine D2 receptors and dopamine metabolism. Relationship between biochemical and behavioural effects of substituted benzamide drugs.
The effect of the substituted benzamide dopamine D2 receptor antagonists sulpiride, raclopride, FLA 966(-), FLA 988(-), eticlopride and remoxipride as well as the "classical" dopamine antagonists, haloperidol and chlorpromazine, on the concentrations of dopamine, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the brain of the rat was investigated. All compounds increased the turnover of dopamine, as defined by increased concentrations of DOPAC and HVA (without change in the concentration of dopamine) in the striatum in a dose-dependent manner. The doses of the compounds producing increased turnover of dopamine in the striatum were in the same range as those displacing the in vivo binding of [3H]spiperone in the striatum. In addition, for all the compounds tested in the study, an increase in the turnover of dopamine to about 300% of control was observed for doses antagonising the stereotypy produced by the dopamine agonist, apomorphine. On the other hand, no consistent relationship between increased turnover of dopamine and the doses of the compounds required to antagonise apomorphine-induced hyperactivity was found. This result was also found in limbic areas. Remoxipride and haloperidol had little or no effect on the turnover of dopamine in either the hypothalamus or substantia nigra at the ED50 doses of these compounds for antagonism of apomorphine-induced stereotypy.
3,4-Dihydroxyphenylacetic Acid↗
Anatomical evidence for direct projections from the entorhinal area to the entire cortical mantle in the rat.
The entorhinal area is the most highly differentiated cortical field of the hippocampal formation from an anatomical point of view, and is best known as the origin of the perforant pathway, a massive association projection to the molecular layer of the dentate gyrus and Ammon's horn. This pathway is important as the first link in the so-called "trisynaptic circuit," which is thought to form the basic unit of information processing in the hippocampal formation and has been implicated in the elaboration of short-term memory and the more permanent storage of selected events in other parts of the cortical mantle. We have reexamined the efferent projections of the lateral entorhinal area with a sensitive new method that utilizes the anterograde axonal transport of a lectin, Phaseolus vulgaris leukoagglutinin (PHA-L), that is not internalized by fibers of passage, and displays labeled axons with the clarity of Golgi impregnations. The results of 5 experiments with injections confined entirely to the lateral entorhinal area suggest that this area sends fibers to innervate the entire cortical mantle, as well as to a longitudinal zone extending the length of the striatum (nucleus accumbens and medial caudoputamen) and the basolateral complex of the amygdala. In an additional series of experiments, injections of the fluorescent retrograde tracer fast blue that were centered in medial prefrontal, somatosensory, auditory, and motor areas of the cortex invariably labeled many neurons in layer IV of the lateral entorhinal area, as well as in other layers, depending on the site of injection. Finally, the results of double retrograde tracer experiments indicated that the 2 densest projections from the lateral entorhinal area--to the medial prefrontal region and to the dentate gyrus and Ammon's horn--arise from essentially separate populations of neurons. These findings serve to clarify the neural mechanisms underlying the role of the hippocampal formation in learning and memory, as well as in locomotor activity associated with goal-oriented behavior.
Animals↗
Effects of intracerebral injections of quinolinic acid on serotonergic neurons in the rat brain.
The effects of intrastriatal and intrahippocampal injections of the excitotoxic amino acid, quinolinic acid (QUIN), were examined in the rat using immunohistochemical and neurochemical techniques. Serotonin and 5-hydroxyindoleacetic acid measurements at 90 min, 6 h, 4 and 11 days following QUIN administration revealed highly elevated levels of the metabolite in the injected nuclei, with peak increases occurring after 4 days. Serotonin levels remained largely unchanged over the same time period. Direct visualization of hippocampal serotonergic fibers by immunohistochemistry demonstrated morphological changes (varicosities, swellings) in otherwise undamaged serotonin-positive afferents 4 days following a local QUIN injection. Hippocampal serotonin turnover was assessed at 4 days after an intrahippocampal QUIN-application: following inhibition of aromatic amino acid decarboxylase, the accumulation of 5-hydroxytryptophan was twice as rapid in QUIN-lesioned hippocampi as in controls. Dose-response relationships, examination of brain regions distant from the two injection sites and the temporal sequence of the changes described here suggest a close association between QUIN-induced neuronal degeneration and alterations in the serotonergic system.
Animals↗
Specific in vitro and in vivo binding of 3H-raclopride. A potent substituted benzamide drug with high affinity for dopamine D-2 receptors in the rat brain.
The substituted benzamide drug raclopride, [((-)-(S)-3,5-dichloro-N-((1-ethyl-2-pyrrolidinyl) methyl)-6-methoxy-salicylamide tartrate; FLA 870(-); A40664] was shown to be a potent and selective antagonist of dopamine D-2 receptors by its high affinity for striatal 3H-spiperone binding sites and low potency to block dopamine stimulated adenylate cyclase in vitro. In vitro studies showed that 3H-raclopride binds with a high affinity (KD = 1.2 nM) and a low proportion of non-specific binding to rat striatal homogenates. The binding of 3H-raclopride is saturable (Bmax = 23.5 pmoles/g wet wt) and reversible (dissociation half-time = 30 min) with a regional distribution of the specifically bound drug showing the following rank-order: striatum greater than nucleus accumbens greater than olfactory tubercle greater than septum greater than hypothalamus greater than hippocampus greater than frontal cortex. After in vivo administration, 3H-raclopride accumulates preferentially in dopamine rich brain areas with approximately 10 times higher levels in the striatum than in the cerebellum, when examined 30 min after injection. The in vivo binding of 3H-raclopride was saturable, reversible and showed a low component of non-specific binding. More than 90% of the drug reached the brain in a non-metabolized form as judged by thin-layer chromatography. Pharmacological analysis of 3H-raclopride binding showed that it could be displaced by dopamine agonists and antagonists but not by serotoninergic or noradrenergic drugs. Taken together, the results suggest that 3H-raclopride labels dopamine D-2 receptors with high specificity in the rat brain both in vitro and in vivo, and thus, that it should be a useful tool in studies of central dopamine D-2 receptors.
Adenylyl Cyclases↗
Intrinsic projections of the retrohippocampal region in the rat brain. I. The subicular complex.
The intrahippocampal projections of the subicular complex were studied in the rat with the aid of the anterogradely transported lectin Phaseolus vulgaris leucoagglutinin (PHA-L). After iontophoretic injections of the lectin into the subiculum proper, presubiculum, or the parasubiculum, axons and terminal processes immunoreactive for PHA-L were traced to their respective terminal fields within the hippocampal region. After subicular injections PHA-L-stained axons could be followed both in a caudal and a rostral direction. The caudally directed fibers course around or within the angular bundle to enter layers VI and V of the medial entorhinal area (MEA). Many fibers penetrate through these layers to terminate in layer IV of the medial and the lateral entorhinal area, which contains a major terminal field of this projection. At more ventral levels, all layers of the entorhinal area are innervated by cells located in the subiculum. Other retrohippocampal projections of the subiculum proper include the deep and the outer two layers of the presubiculum and the medial sector of the parasubiculum, in addition to a massive projection which terminates in the retrosplenial cortex. The rostrally directed projections from the subiculum form a dense innervation of strata lacunosum, radiatum, oriens, and of individual pyramidal cells in the regio superior of the Ammon's horn. All these projections of the subiculum are exclusively ipsilateral. After injections of PHA-L into layers II and III of the presubiculum, both ipsi- and contralateral projections were traced to the outer three layers of the medial entorhinal area; the lateral entorhinal area apparently receives no innervation from the presubiculum. The innervation of layer III is very dense while in layer II and deep layer I, restricted zones of innervation are found. The fibers reach these layers via the deep layers of the MEA and through the molecular layer after first coursing around the parasubiculum. In addition, a minor projection from the presubiculum to the pyramidal cell layer of the subiculum and to the molecular layer of the hippocampal formation was found. PHA-L injections into the parasubiculum labeled fibers that form a dense innervation of layer II in the MEA and the medial part of the lateral EA, and of the most medial sector of layer III in the MEA. Layer I and the superficial part of layer II of the contralateral MEA also contain a dense terminal network after PHA-L injections into the parasubiculum.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Immunocytochemical localization of glutamic acid decarboxylase and substance P in the lateral cervical nucleus: a light and electron microscopic study in the cat.
Using immunocytochemical technique, the light and electron microscopic localization of substance P and glutamic acid decarboxylase (GAD) immunoreactivity in the feline lateral cervical nucleus (LCN) has been investigated. A dense substance P labeling, confined mainly to boutons contacting dendritic profiles, was demonstrated in the ventromedial part of the LCN. GAD-positive boutons, frequently in contact with cell bodies, were found scattered throughout the nucleus. The results suggest that gamma-aminobutyric acid is an inhibitory transmitter in the LCN. The role of the substance P is unclear. Its distribution, however, supports the concept of a separate function of the ventromedial part of the LCN.
Animals↗
Some in vitro receptor binding properties of [3H]eticlopride, a novel substituted benzamide, selective for dopamine-D2 receptors in the rat brain.
The substituted benzamide compound eticlopride, (S)-(-)-5-chloro-3-ethyl-N-[(1-ethyl-2-pyrrolidinyl) methyl]-6-methoxysalicylamide hydrochloride (FLB 131), has been shown to selectively block dopamine-D2 binding sites in the rat brain. The compound was tritium-labelled to high specific radioactivity and was used for in vitro receptor binding studies. [3H]Eticlopride was found to bind specifically to rat brain homogenates with the highest binding in the striatum and lowest in the hippocampus. The binding was saturable with a high number of binding sites (49.5 pmol/g) and with very high affinity (0.17 nM). As with other benzamides, the binding of [3H]eticlopride was highly sodium-dependent. Lesioning of the striatal neurons with ibotenic acid reduced the binding by 50% while lesioning of the nigrostriatal pathways with 6-hydroxydopamine was without effect on the observed binding. The binding of [3H]eticlopride was inhibited potently by neuroleptic drugs, while compounds known not to interact with the dopamine-D2 binding sites were inactive. It is concluded that this new dopamine-D2 antagonist may be a useful tool for the study of dopamine-D2 binding sites due to its high affinity and good selectivity.
Animals↗
A projection from the deep layers of the entorhinal area to the hippocampal formation in the rat brain.
The methods of retrograde fluorescent tracing and anterograde transport of the lectin Phaseolus vulgaris leucoagglutinin (PHA-L) were used to demonstrate the existence of projections from layers IV and VI of the entorhinal area to the hippocampal formation in the rat brain. These two layers of the medial and lateral entorhinal area innervate the molecular layer of Ammon's horn and the area dentata. In the area dentata the projection from layer IV follows that of the perforant path, while that from layer VI innervates the outer two-thirds of the molecular layer, the subgranular zone and the deep part of the hilus of the area dentata.
Amidines↗
Neurons and terminals in the retrohippocampal region in the rat's brain identified by anti-gamma-aminobutyric acid and anti-glutamic acid decarboxylase immunocytochemistry.
The distribution of gamma-aminobutyric acid (GABA) containing nerve cells and terminals was studied at the light and electron microscopic levels in the retrohippocampal region of the rat by using anti-glutamic acid decarboxylase (GAD) and anti-GABA antibodies in immunocytochemistry. Large numbers of GAD and GABA stained cells were found in all retrohippocampal structures. At the ultrastructural level, the immunoreactivity against GABA and against the synthesizing enzyme GAD was localized to cytoplasmic structures, including loose clumps of rough endoplasmic reticulum, ribosomal arrays, outer mitochondrial surfaces and in axonal boutons. The GAD- and GABA-immunoreactive(-i) cells were found in all subfields of the retrohippocampal region (e.g., the subicular complex, the entorhinal area). Within the entorhinal area a slightly larger number of immunoreactive cells could be detected in layers II and III than in the other layers. In the subiculum, pre- and parasubiculum the GAD and GABA-i cells were present in relatively large numbers in all layers, except the molecular layer, which contained only a small number of GABA cells. Within the entorhinal area, GAD and GABA stained cells ranged in size from small (13 micron in diameter) to large (22 micron in diameter). A large number of different morphological classes of cells were found, except pyramidal and stellate cells. In the pre- and parasubiculum, on the other hand, the GABA cells were generally small to medium in size and morphologically more homogeneous than in the subiculum and entorhinal area. The entire retrohippocampal region was densely innervated by GABA preterminal processes, with little variation in the regional density of innervation. Within the entorhinal area, presubiculum and subiculum, a clear difference was found in the laminar pattern of innervation. In all three subfields the densest innervation was in layer II. In the entorhinal area both GAD- and GABA-i axons form palisades of fibers around the somata of neurons, which are tightly packed together in this layer. In the electron microscope both GAD-i and GABA-i were demonstrated in these axons. Axosomatic synaptic contacts were common between axons and the stellate neurons and other cells of this layer. Layers IV and VI appeared less dense in GAD-i terminals but appeared more densely innervated than layers III and V. The lamina dessicans was relatively poor in GAD-i. In the subiculum and presubiculum, as well as all other subfields of the hippocampal region, the innervation is dominated by axo-somatic innervation of layer II cells.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
The substance P innervation of the rat hippocampal region.
The distribution of substance P (SP) immunoreactive nerve cell bodies and preterminal processes was studied in the rat brain by using several anti-SP-antibodies in combination with immunohistochemical techniques. In normal rats and in rats pretreated with colchicine, SP immunoreactive preterminal processes were found in the hippocampal region, but SP positive cellbodies could be detected only after colchicine pretreatment. Medium-sized to large, multipolar cells immunoreactive for SP were found in stratum oriens of the hippocampal subfield CA 3 and in the hilus of the area dentata. Medium-sized to small, round or fusiform cells were detected in the pyramidal layer of the ventral subiculum and in layers III-VI of the ventral entorhinal area. The SP stained preterminal processes were of two types. Numerous fine, varicose axons were stained in different parts of Ammon's horn, while in the retrohippocampal structures, the SP immunoreactivity was present in small distinctly stained puncta. These frequently formed pericellular arrangements around unstained cells, indicative of axosomatic contacts between SP terminals and cells in the hippocampus. In Ammon's horn, the densest SP innervation was found in strata oriens, radiatum and moleculare of subfields CA 3a and CA 2. Scattered fibers were also present in the stratum oriens of CA 3a-c and in the hilus, in particular at ventral levels. In retrohippocampal structures, the SP innervation predominated in the deep pyramidal layer of the subiculum, the second layer of the presubiculum and in layers VI and IV of the medial and lateral entorhinal area.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Specific in vivo binding of 3H-spiperone to individual lobes of the pituitary gland of the rat. Evidence for the labelling of dopamine receptors.
The in vivo binding of 3H-spiperone to individual lobes of the pituitary gland was studied after intravenous injections in unanesthetized male rats. The binding was found to be saturable and reversible. The percentage of total binding of 3H-spiperone that was specific binding was highest in the intermediate (approximately equal to 75%) and lowest in the posterior (approximately equal to 35%) lobes. The regional distribution of 3H-spiperone binding 1 hour after injections was the following: intermediate greater than anterior greater than posterior. Pharmacological analysis of the in vivo 3H-spiperone binding showed that dopamine agonists (e.g. bromocriptine, N-n-propylnorapomorphine) and antagonists could prevent the in vivo binding of 3H-spiperone in all three parts of the gland. The substituted benzamide drugs remoxipride and raclopride blocked the in vivo 3H-spiperone binding in the anterior and intermediate lobes but did not reduce the 3H-spiperone binding in the posterior part, except when given in very high doses. Taken together, the present study has shown that 3H-spiperone can be used in studies of the dopamine receptors in the anterior, intermediate and posterior lobes of the pituitary gland, but the proportion of non-specific binding is higher than in the striatum. The use of in vivo 3H-spiperone binding may thus be a useful method to study the regulation and pharmacology of these receptors in situ.
Animals↗
The cytoarchitecture, histochemistry and projections of the tuberomammillary nucleus in the rat.
The normal morphology, efferent projections and possible neurotransmitter content of neurons in the tuberomammillary nucleus (caudal magnocellular nuclei of Bleier et al.) [Bleier, Cohn and Siggelkow (1979) In Anatomy of the Hypothalamus, Vol. 1, pp. 137-220] have been examined in the adult male rat. In Nissl-stained sections, the nucleus can be divided into a dorsomedial, ventral and diffuse part, each of which consists of large, darkly stained neurons cradling the mammillary body. The ventral part is by far the largest and consists of some 2500 neurons on each side of the brain. Immunohistochemical studies indicate that a majority of the large neurons in all three parts of the nucleus stain with antisera against glutamate decarboxylase and [Met]enkephalyl-Arg6-Phe7 heptapeptide and that a smaller subset of these neurons (about 10%) also stain with an antiserum against substance P. Single injections of retrogradely transported fluorescent tracers were made into 18 different sites in 86 animals and the results indicate that all three parts of the tuberomammillary nucleus on one side of the brain send fibers to or through various parts of the neocortex, hippocampal formation, amygdala, basal ganglia, thalamus, superior colliculus and cerebellum on both sides of the brain and that the projection neurons are not organized in a highly topographic way. Injections of two different fluorescent tracers in the same animal indicate that individual neurons in the nucleus may give rise to both ascending and descending projections, as well as projections to widely divergent parts of the forebrain. Together with previous results, this evidence suggests that the tuberomammillary nucleus has widespread projections to the numerous brain structure located in the forebrain and in the caudal medulla (it may not project to the spinal cord), and that its axons may release a mixture of neuroactive substances including gamma-amino butyrate and several peptides. Although its functional significance remains to be investigated, morphological evidence suggests that the tuberomammillary nucleus may constitute one of a series of neurotransmitter-specific cell groups in the brainstem and basal forebrain with diffuse efferent projections that may be involved in the modulation of attention or behavioral state, rather than the processing of specific sensory or motor information.
Amidines↗
Autoradiographic localization of [3H]neurotensin-binding sites in the hippocampal region of the rat and primate brain.
The distribution of binding sites for the neuropeptide neurotensin was studied in the hippocampal region of the rat, monkey and human brain by using the method of in vitro receptor autoradiography. Biochemical studies of [3H]neurotensin binding to homogenates or sections of the rat hippocampal region showed it to be saturable, reversible and of high specificity. Displacement studies showed that neurotensin-(1-13) and neurotensin-(8-13) were active, while neurotensin-(1-6) and (1-8) were inactive in blocking the specific binding of [3H]neurotensin to hippocampal sections. The autoradiographic studies showed a highly heterogeneous pattern of [3H]neurotensin binding in the hippocampal region: the highest density was present in the entorhinal area while little binding was found in the Ammon's horn. In the rat most of the [3H]neurotensin binding was found in layer II of the medial entorhinal area and in the parasubiculum, while the lateral entorhinal area contained fewer [3H]neurotensin-binding sites. The laminar distribution of binding remained the same throughout the longitudinal axis of the entorhinal area. The pattern of [3H]neurotensin binding in the monkey resembled that seen in the rat inasmuch as the medial was rich and the lateral entorhinal area was poor in [3H]neurotensin-binding sites. In the medial entorhinal area most binding was found in layers I-IV. Unlike in the rat, the hilus of the monkey contained moderate and the molecular layer of the area dentata few [3H]neurotensin-binding sites. In the human brain the outer three layers of both the medial and the lateral entorhinal area contained binding sites for [3H]neurotensin. Binding sites for [3H]neurotensin were found also in the parasubiculum and in the molecular layer of the area dentata of the human brain. The present autoradiographic studies show that the hippocampal region of the rat and primate brain is rich in binding sites for [3H]neurotensin, that a majority of these are situated in the entorhinal area and that despite some differences in the regional distribution of these binding sites within the hippocampal region, some principal similarities may exist between these species.
Animals↗
[Selective antidopaminergic properties of remoxiprid, a new potential antipsychotic agent].
The pharmacology of S-(-)-3-bromo-2, 6-dimethoxy-N-(1-ethyl-2-pyrrolidinylone-ethyl)-benzamide (remoxipride), a new neuroleptic compound belonging to the benzamide group, has been thoroughly investigated using a number of different techniques. The compound blocks apomorphine-induced stereotypies and hyperactivity, indicating potent antidopaminergic activity. However, in contrast to many other antidopaminergic compounds, remoxipride induces only weak and atypical catalepsy, which indicates that remoxipride might exert less antidopaminergic side effects than other neuroleptic drugs. In vivo receptor binding studies using 3H-spiperone show that remoxipride preferentially blocks dopamine receptors only are blocked to 60% even at very high doses. In vitro receptor binding studies show that remoxipride is devoid of affinity for receptors other than the dopamine D2 receptors except at higher concentrations. These results indicate that remoxipride should be a clinically effective neuroleptic compound exerting less extrapyramidal side effects than the neuroleptics currently used.
Animals↗
[Fertility and Turner syndrome].
A case of Turner's syndrome (45,X/47,XXX) with one pregnancy is reported. Review of the literature revealed additional 31 cases of fertility in women with gonadal dysgenesis associated with a 45,X chromosomal line. Abortion and stillbirth are frequent and the rate of malformation is high.
Adult↗
The ergolene derivative MPME induces in the rat a behavioural syndrome associated with activation of dopamine D-1 receptors belonging to the dotted type of forebrain dopamine nerve terminals.
The ergolene derivative MPME (PTR 17402; (5R,8R)-8-(4-p-methoxyphenyl)-1-piperazynylmethyl-6- methylergolene], a dopamine (DA) receptor agonist acting mainly at DA D-1 receptors linked to dotted types of forebrain DA nerve terminals, induces a characteristic behavioural syndrome consisting of increased locomotion, head-bobbing and sniffing activity without oral stereotypies or increased rearing. Haloperidol and cis-flupenthixol, nonselective DA receptor antagonists, but not selective D-2 receptor antagonists such as remoxipride and sulpiride, could significantly counteract the locomotion and head-bobbing behaviour induced by MPME. In contrast, the sniffing behaviour induced by MPME was only marginally affected by haloperidol and cis-flupenthixol pretreatment. These results suggest that activation of D-1 receptors in the forebrain mainly linked to the dotted types of DA nerve terminals in the striatum, and in the limbic forebrain, can result in behavioural effects which differ from those caused by stimulation of D-2 receptors located mainly within the diffuse types of DA nerve terminal systems.
Animals↗