Biomedical subjects

D W Pfaff

Publications and source records attributed to D W Pfaff.

At least 271 records · Page 15Linked to original sources

PubMed1988

Opioidergic modulation of the oestradiol-induced LH surge in the rat: roles of ovarian steroids.

Sex steroids convey information on the status of the reproductive system, which the brain is able to integrate to promote ovulation, in the form of the LH surge. The present studies examined the influence of alterations in central opioidergic tone to initiate the LH surge, and the roles of oestradiol and progesterone to effect changes in opioidergic tone, by antagonizing this activity using either naloxone or nalmefene (N-cyclopropylmethyl-6-desoxy-6-methylene-noroxy-morphone), a long-acting mu- and kappa-opiate antagonist. The timing and amplitude of the LH surge was examined in (1) cyclic rats in pro-oestrus and (2) ovariectomized rats with varying doses of oestradiol supplementation. Plasma was obtained hourly through an indwelling intra-atrial catheter between 13.00 and 19.00 h, and later assayed for LH and oestradiol concentrations by radioimmunoassay. Rats treated with either nalmefene or progesterone on pro-oestrus demonstrated similar advances in the time of initiation of the LH surge by 1-2 h compared with control rats. The effects of nalmefene and progesterone were evident within 2 and 3-5 h of their administration respectively. Conversely, rats treated with progesterone on dioestrus demonstrated low pro-oestrous oestradiol levels and abolition of the pro-oestrous LH surge, but continuous naloxone infusion restored the pro-oestrous LH surge, with raised oestradiol concentrations. In ovariectomized rats without oestradiol supplentation, nalmefene alone was able to increase basal LH levels, but unable to facilitate a spontaneous rise in LH amplitude indicative of an LH surge. Supplementation with low doses of oestradiol was itself ineffective in facilitating a spontaneous rise in LH concentration, but nalmefene co-administration significantly potentiated the ability of low doses of oestradiol to induce augmented LH secretion, in addition to advancing the timing of the spontaneous LH rise. Similarly, progesterone co-administration to ovariectomized, oestradiol-primed rats significantly advanced and augmented LH hypersecretion. The results of these experiments are consistent with the concept that central opioidergic systems normally restrain the initiation of the LH surge, and that blocking opiate receptors removes this inhibition. They advance the hypothesis that oestradiol, the essential signal for LH surge induction, has, as one consequence of its action, the time-specific inhibition of hypothalamic opiodergic tone in the afternoon, which would otherwise restrain the LH surge-generating mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Induction of LH hypersecretion in cyclic rats during the afternoon of oestrus by oestrogen in conjunction with progesterone antagonism or opioidergic blockade.

The pro-oestrous secretion of progesterone that follows the LH surge in the rat limits the expression of the daily signal for LH surge initiation until the following oestrous cycle. This study explored the role of endogenous opioid peptides in the extinction by progesterone of the signal for the LH surge induced by oestrogen. Intact cyclic rats underwent external jugular venous cannulation on dioestrus, and were allowed to elicit a spontaneous pro-oestrous LH surge. On the afternoon of pro-oestrus, rats received an s.c. injection of oestradiol and an s.c. injection of either oil, 17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(prop-1-ynyl)oestra-4,9,dien-3-one (RU 486; a synthetic anti-progestin), or N-cyclopropylmethyl-6-desoxy-6-methylene-noroxy-morphone (nalmefene; a long-acting opiate antagonist). Repeat doses of each were administered on the morning of oestrus to maintain increased oestrogen levels, and either progesterone or opioidergic blockade. Plasma was obtained from 13.00 to 19.00 h on oestrus for determination of the concentration of rat LH. Rats treated with oestradiol alone demonstrated consistently low concentrations of LH throughout the afternoon of oestrus. Rats treated with both oestradiol and either RU 486 or nalmefene demonstrated spontaneous augmentations of rat LH concentration during the afternoon of oestrus, which, although of diminished amplitude as compared with that seen in pro-oestrus, were consistent with a reactivation of the LH surge-generating mechanism. Rats treated with nalmefene in the absence of oestradiol were unable to augment LH secretion spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1988

Vasopressin gene expression in hypertensive, normotensive, and diabetes insipidus rats.

This investigation examined the presence and abundance of vasopressin-gene messenger ribonucleic acid (mRNA) transcripts in hypothalamic tissue from five strains of rats: Long Evans, Wistar-Kyoto, and diabetes insipidus (Brattleboro) rats, stroke-prone spontaneously hypertensive rats, and cross-bred diabetes insipidus x stroke-prone spontaneously hypertensive rats. A single-stranded RNA probe complementary to exon C of the vasopressin gene was utilized for in situ hybridization and identified hypothalamic 'vasopressinergic' neurons in tissue from all five strains of rats. The results obtained by solution and in situ hybridization suggested the cross-bred diabetic-hypertensive rat exhibits a level of vasopressin-gene messenger ribonucleic acid similar to diabetes insipidus rats. This observation is consistent with previous physiological data which suggests cross-bred diabetic-hypertensive rats inherit the mutated vasopressin gene of the Brattleboro rat.

Animals↗

PubMed1988

An estradiol-induced protein synthesized in the ventral medial hypothalamus and transported to the midbrain central gray.

Estradiol (E2) facilitates the lordosis reflex that occurs in response to flank stimulation in female rats. Lordosis appears to be regulated in part by the synthesis of proteins in the ventral medial hypothalamus (VMH) that are transported to the midbrain central gray (MCG). We developed a strategy involving microinfusion of radioactive amino acids, followed by 2-dimensional gel electrophoresis, to identify proteins that may be regulated by E2 in the VMH and transported to the MCG. A mixture of 35S-methionine and 35S-cysteine (2:1, total 500-1000 microCi), suspended in 1 microliter PBS, was infused bilaterally into the VMH over a period of 2 hr into matched pairs of ovariectomized female rats, one of which was given a Silastic implant containing E2 at the beginning of infusion or 1 week earlier. The rats were sacrificed 12 hr after the end of infusion, and several brain regions were obtained by microdissection. Samples were analyzed by 2-dimensional gel electrophoresis, entailing isoelectric focusing in the first dimension and SDS-PAGE (molecular-weight separation) in the second dimension, followed by fluorography. We could routinely separate at least 250 spots. We consistently found a protein spot with an apparent molecular weight of 70 kDa, pI of about 5.9, which almost always appeared in the VMH and MCG of rats given E2 replacement but very rarely in samples from ovariectomized rats given no E2 replacement. A spot immediately acidic to this protein (70 kDa, pl about 5.8) appeared to vary inversely with this E2-induced protein.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1987

Electrical stimulation of the midbrain central gray facilitates lateral vestibulospinal activation of back muscle EMG in the rat.

Electrical stimulation in the midbrain central gray in urethane-anesthetized female rats increased responses of the deep back muscles lateral longissimus and medial longissimus to stimulation of the lateral vestibular nucleus (LVN). During central gray stimulation, LVN stimuli led to larger muscle responses, recruitment of new motor units, and decreased latency of muscle response. Effective central gray sites are hypothesized to act through axons descending to medullary reticular formation. Results are consistent with participation of these neuronal groups in the activation of lordosis behavior, a vertebral dorsiflexion that requires deep back muscle contraction, but these electromyographic results could also be relevant for other behaviors that require vertebral postural adjustments.

Action Potentials↗

PubMed1987

Responses of ventromedial hypothalamic neurons in vitro to norepinephrine: dependence on dose and receptor type.

Application of norepinephrine (NE) at 12.5 microM in the bath surrounding hypothalamic slices from ovariectomized rats could evoke excitation, inhibition, or biphasic inhibition-excitation from single neurons in the ventromedial nucleus. Whether the rats were treated with estrogen or not did not alter the distribution of the type of neuronal responses to NE in vitro. Altering the composition of the bathing solution to achieve synaptic blockade did not abolish or alter the type of responses, indicating that all these types of NE responses, including both phases of the biphasic response, were mediated by postsynaptic receptors. Experiments with varying doses of NE showed that the inhibitory response could be evoked at doses lower than those required to evoke the excitatory response. The effective dose for 50% of the responsive neurons (ED50) was lower than 1.25 microM for inhibitions and higher than 5 microM for excitations. Using specific adrenergic receptor agonists and antagonists, it was found that the excitation and the inhibition were mediated, primarily, by alpha 1- and alpha 2-receptors, respectively. beta-Receptors played only a minor role, but might be related to both excitation and inhibition. Study with adrenergic agents further revealed that different types of adrenergic receptors co-localized not only in neurons showing the biphasic response, but also in a major portion of neurons showing monophasic excitation or inhibition. Because of the co-localization and the differential sensitivities to NE, alteration of the dose of NE or the ratio of excitatory/inhibitor receptors co-localized on a neuron should be able to reverse the type of a neuronal response to NE.

Animals↗

PubMed1987

Localization of preproenkephalin mRNA in the rat brain and spinal cord by in situ hybridization.

To determine the localization in rat brain and spinal cord of individual neurons that contain the messenger RNA coding for the opioid peptide precursor preproenkephalin, we performed in situ hybridization with a tritiated cDNA probe complementary to a protion of preproenkephalin mRNA. We observed autoradiographic signal over the cytoplasm of neurons of many regions of the central nervous system. Several types of controls indicated specificity of the labeling. Neurons containing preproenkephalin mRNA were found in the piriform cortex, ventral tenia tecta, several regions of the neocortex, nucleus accumbens, olfactory tubercle, caudate-putamen, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, preoptic area, amygdala (especially central nucleus, with fewer labeled neurons in all other nuclei), hippocampal formation, anterior hypothalamic nucleus, perifornical region, lateral hypothalamus, paraventricular nucleus, dorsomedial and ventromedial hypothalamic nuclei, arcuate nucleus, dorsal and ventral premamillary nuclei, medial mamillary nucleus, lateral geniculate nucleus, zona incerta, periaqueductal gray, midbrain reticular formation, ventral tegmental area of Tsai, inferior colliculus, dorsal and ventral tegmental nuclei of Gudden, dorsal and ventral parabrachial nuclei, pontine and medullary reticular formation, several portions of the raphe nuclei, nucleus of the solitary tract, nucleus of the spinal trigeminal tract (especially substantia gelatinosa), ventral and dorsal cochlear nuclei, medial and spinal vestibular nuclei, cuneate and external cuneate nuclei, gracile nucleus, superior olive, nucleus of the trapezoid body, some deep cerebellar nuclei, Golgi neurons in the cerebellum, and most laminae of the spinal cord. In most of these brain regions, the present results indicate that many more neurons contain preproenkephalin mRNA than have been appreciated previously on the basis of immunocytochemistry.

Animals↗

PubMed1987

Brainstem reticular stimulation facilitates back muscle motoneuronal responses to pudendal nerve input.

In urethane or pentobarbital anesthetized female rats, stimulation with bipolar electrodes in the medullary reticular formation evoked activity in lateral longissimus muscle nerves, when trains of pulses were applied. Combined stimulation of the medullary reticular formation and the pudendal nerve revealed a marked mutual facilitation of their two separate effects on the excitability of the lateral longissimus muscle nerves. These results match previous conclusions based on the effects of spinal column transection on the pudendal nerve-evoked response, and are consistent with a role for this mutual facilitation in the control of lordosis behavior.

Animals↗

PubMed1987

Effects of total and partial spinal transections on the pudendal nerve-evoked response in rat lumbar axial muscle.

The pudendal nerve-evoked activity in lumbar axial muscle nerves 24-48 h following spinal transections was studied in order to examine the supraspinal control of the pudendal nerve-evoked response (PNER). After total transections of the spinal cord in the thoracic region the overall activity in the muscle nerves was much reduced; the evoked responses consisted only of a single peak in activity 19.8 ms (+/- 1.4 ms) following the last shock of a 3-shock pudendal nerve stimulus demonstrating that some of the earliest responses previously described for the PNER are segmental in origin. To help identify supraspinal inputs to the PNER a series of partial transections were made to cut selectively different fiber columns within the cord. Four different surgical procedures were performed: transections of the entire dorsal half of the cord; ablations of all of the medial columns; combined lesions of the dorsal half and medial columns, sparing the tracts within the ventrolateral columns and bilateral transections of the lateral columns. Following all partial transections except those of the lateral columns, the PNER was similar to that seen in intact animals. After lateral column transections however, the responses were like those seen in the totally transected animals. The combined results suggest that supraspinal influences upon the PNER are conveyed primarily via the ventrolateral columns of the spinal cord. Bilateral convergence of afferent information was evident in the totally transected animals, indicating that such convergence can occur at segmental levels. The lesions which substantially altered the PNER closely paralleled those which eliminated lordotic responsiveness in behaving female rats.

Animals↗

PubMed1987

Distribution of luteinizing hormone-releasing hormone in the nervus terminalis and brain of the mouse detected by immunocytochemistry.

Immunoreactive luteinizing hormone-releasing hormone (LHRH) was localized in a relatively large number of ganglion cells and fibers of the nervus terminalis of neonatal and adult mice, indicating that this nerve is a substantial source of LHRH in the mouse brain. Whole-head specimens of neonatal mice, prior to calcification of the cranium, revealed an extensive distribution of LHRH neurons and fine fibers throughout the peripheral, intracranial, and central parts of the nervus terminalis. The most striking difference between the neonatal and adult animals, in the nervus terminalis, was the increase in immunoreactive axons that made up the fiber bundles of this nerve. In the adult mouse, the intracranial and central projections were composed of thick fascicles of immunoreactive axons, ensheathed by glial cells and accompanied by ganglia that contained both LHRH-reactive and nonimmunoreactive neurons. LHRH-immunoreactive cells and axons were seen in a branch of the nervus terminalis that coursed along the medial, posterodorsal aspect of the olfactory bulb and in branches of this nerve that accompany the vomeronasal nerves to the accessory olfactory bulb. A few LHRH neurons and many immunoreactive processes were seen in the accessory and main olfactory bulbs. LHRH-reactive neurons were seen in the hypothalamus and extrahypothalamic structures. Examination of adult mouse brains revealed a pattern of distribution and number of immunoreactive neurons similar to that seen in the neonate. However, many more LHRH-reactive axons were seen in all areas of the brain of the mature animal.

Age Factors↗

PubMed1987

Neuropeptides TRH and cyclo(His-Pro) share neuromodulatory, but not stimulatory, action on hypothalamic neurons in vitro: implication for the regulation of feeding.

Electrical activity of neurons in rat hypothalamic ventromedial nucleus was recorded in tissue slices, to investigate central neural mechanisms underlying reduction of food intake caused by TRH and its metabolite, cyclo(His-Pro) [cHP]. Application of TRH had two actions: stimulation of neuronal activity, which was desensitized on closely repeated applications; and modulation of neuronal responses to neurotransmitters, even in the absence of the stimulatory action. The neuromodulatory but not the direct stimulatory action could also be achieved by cHP. The neuromodulatory action is more likely to be a neural mechanism underlying the inhibition of feeding, while other biological functions, unique to TRH, may depend on direct stimulation. In this way, TRH could achieve different biological results through different modes of action on hypothalamic neurons.

Action Potentials↗

PubMed1987

LHRH messenger RNA in neurons in the intact and castrate male rat forebrain, studied by in situ hybridization.

The purpose of the present study was to localize luteinizing hormone-releasing hormone (LHRH) mRNA within the male rat forebrain using an in situ hybridization approach. The expression of LHRH mRNA was compared in castrate and intact males to approach questions on the chronic influences of circulating testicular steroids on the gene expression of the peptide. Frozen 10 micron sections fixed in paraformaldehyde were obtained from the forebrain region of intact and 2 week post-castrate adult male rats. LHRH mRNA was autoradiographically detected using an oligomer (59mer) complementary to the mRNA coding for amino acids -5 to 15 of the human LHRH preprohormone. Individual brain sections were incubated in prehybridization buffer for 2 h to reduce nonspecific binding. Following this, 20 microliter of hybridization buffer containing 65,000-120,000 cpm of the 59mer were applied to sections and hybridized at 37 degrees C for 3 days. The sections were then rinsed over a 48 h period, dehydrated, dipped in Kodak NTB2 liquid emulsion and exposed for 22 days. Autoradiograms were developed and counterstained with fast green and cresyl violet. As reported in the female, LHRH message-containing cells were localized in ventral septal regions, the diagonal bands of Broca, preoptic area and anterior hypothalamus. On occasion, LHRH gene expressing cells were found to appear in loose clusters. Labeled cells were never found in control sections treated with hybridization buffer lacking the 59mer. The total number of LHRH mRNA-containing cells localized in intact rats did not differ significantly from the castrate group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Quantitative assessment of the synergistic and independent effects of estradiol and progesterone on ventromedial hypothalamic and preoptic-area proteins in female rat brain.

In this study, quantitative assessment of the synergistic and independent effects of estradiol and progesterone on protein synthesis in the ventromedial hypothalamus (VMN) and the preoptic area (POA) was accomplished using in vitro 35S-methionine and 35S-cystein labeling, two-dimensional gel electrophoresis, and computerized densitometry. Ovariectomized (OVX) rats were divided into four groups. Group 1 was implanted with estradiol (E) capsules for 6 hr and injected with progesterone (P; 0.1 ml, 5 mg/ml propylene glycol) at 20 hr. Group 3 was sham-implanted for 6 hr and injected with 0.01 ml P at 20 hr. Group 4 was sham-planted for 6 hr and injected with vehicle alone at 20 hr. All animals were sacrificed at 24 hr. A number of proteins in both VMN and POA were found to be increased or decreased in labeling by E plus P, E alone, and P alone. Two important synergistic effects of the hormones were found. First, the effects of E on labeling of several proteins in both brain regions were countered by P, and conversely, the effects of P on labeling of several proteins in both brain regions were countered by E. Second, E priming increased the number of proteins affected in labeling by P in both brain regions. Comparison of the effects of E and P on proteins in the VMN and POA indicated that the populations of proteins affected in labeling were markedly different. These results begin to clarify the mechanism in which E and P affect neuronal functioning in two regions involved in the control of reproduction and lend support to the hypothesis that gonadal steroids accomplished their action on brain tissue via a mechanism that is partly unique to the brain region.

Animals↗

PubMed1987

Electrical stimulation of the midbrain central gray facilitates reticulospinal activation of axial muscle EMG.

EMG responses were recorded from axial muscles transversospinalis, medial longissimus, and lateral longissimus in urethane-anesthetized rats during combined electrical stimulation of the reticular formation and midbrain central gray. Central gray stimulation facilitated reticular formation-evoked EMG activity in the back muscles of the rat. Electrical stimulation of the central gray lowered the threshold for reticulospinal activation of axial muscles and could maintain firing in these muscles after the end of a reticular formation train. Units were recruited in order of size from small to large. In only one case, central gray stimulation activated axial muscles directly without reticular formation stimulation. The central gray may be important in relaying hypothalamic influences to the reticular formation, which has direct access to the axial muscles responsible for lordosis behavior.

Action Potentials↗

PubMed1987

Localization of steroid-concentrating cells in the central nervous system of the frog Rana esculenta.

Steroid-concentrating cells were localized using steroid hormone autoradiography in the brain of Rana esculenta after systemic administration of tritiated estradiol and testosterone. Highest numbers of labeled cells were found in the anterior preoptic area, in the ventral infundibular nucleus, and in the pituitary. Other sites of tritiated sex steroid uptake were in the striatum, septum, amygdala, thalamus, tectum, torus semicircularis, and dorsal tegmental area of the medulla. No differences were seen between males and females. These results complement the ones obtained in Rana pipiens and confirm that in the genus Rana the distribution of testosterone- and estradiol-concentrating neurons is invariant in many respects.

Animals↗

PubMed1987

Progesterone inhibition of aggressive behaviors in hamsters.

Effects of progesterone on aggressive behaviors were tested in male-male or female-female pairs of hamsters, after both members of the pair had received the same experimental treatment. In castrated males, progesterone increased the latency to attack, and decreased the frequency of attack and on-back fighting postures. Similarly, in ovariectomized females, progesterone decreased the frequencies of upright and attack fighting responses, as well as the frequency of rolling fights. Estradiol treatment did not produce these effects on aggressive behaviors, and was not required to prime the nervous system for the progesterone effects. These results suggest that progesterone may act by means other than estrogen-inducible progestin receptors to inhibit aggressive behaviors.

Aggression↗

PubMed1987

Passive immunization of fetal rats with antiserum to luteinizing hormone-releasing hormone (LHRH) or transection of the central roots of the nervus terminalis does not affect rat pups' preference for home nest.

Luteinizing hormone-releasing hormone (LHRH) is found immunocytochemically in cell bodies and fibers of the nervus terminalis, a cranial nerve which courses from the nasal septum through the cribriform plate of the ethmoid bone (medial to the olfactory and vomeronasal nerves) and enters the forebrain, caudal to the olfactory bulbs. Immunoreactive LHRH is first detected in the nervus terminalis of the fetal rat at 15 days of gestation, preceding its detection by immunocytochemistry in any other area of the brain, including the median eminence, and preceding detection of immunoreactive luteinizing hormone (LH) in the anterior pituitary. During development of the rat fetus, the nervus terminalis is the principal source of LHRH in the nervous system from days 15 through 19 of a 21 day gestation period. We tested the notion that the LHRH system of the nervus terminalis is important for olfactory performance by examining the effects of administration of antisera to LHRH during fetal development (versus saline controls), or medial olfactory peduncle transections, in the neonatal rat, which would sever the central projections of the nervus terminalis (versus lateral peduncle transection, complete transection of the olfactory peduncles and the central nervus terminalis or controls) on preferences of rat pups for home nest. The hypothesis that LHRH is important for this chemosensory response was not confirmed. Neither antisera to LHRH nor medical olfactory peduncle transection disrupted preference for home shavings. Only complete olfactory peduncle transection had a significant effect compared to unoperated and sham-operated controls.

Animals↗

PubMed1987

Haloperidol increases proenkephalin mRNA levels in the caudate-putamen of the rat: a quantitative study at the cellular level using in situ hybridization.

Previous immunocytochemical studies have shown that the opioid peptides, Met-enkephalin and Leu-enkephalin, are present in medium-sized, spiny projection neurons of the caudate-putamen. It has also been demonstrated that chronic treatment of rats with the dopamine receptor blocker, haloperidol, results in an increase in the levels of enkephalin peptides and proenkephalin mRNA in this brain region. To determine whether this increase in proenkephalin mRNA content is exhibited by all enkephalinergic neurons of the caudate-putamen or by only a subpopulation, we have used in situ nucleic acid hybridization to examine the haloperidol-induced increase in proenkephalin mRNA levels at the cellular level. Results of in situ hybridization suggest that all enkephalinergic neurons in the caudate-putamen can respond to haloperidol treatment with an increase in steady state levels of proenkephalin mRNA, and that the mean induction is an approximate 3-fold increase in the message levels. This suggests that dopamine exerts a tonic inhibitory effect on the expression of the proenkephalin gene in all of the enkephalinergic neurons of the caudate-putamen. Dot blot analysis indicated a 2.4-fold increase in the tissue levels of this mRNA. The agreement between the in situ hybridization results and dot blot analysis supports in situ hybridization as a reliable method for quantitative studies of alterations in neuropeptide precursor mRNAs in the brain.

Animals↗