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D W Pfaff

Publications and source records attributed to D W Pfaff.

At least 181 records · Page 10Linked to original sources
PubMed1992

Prolactin receptor messenger RNA is synthesized by the epithelial cells of the choroid plexus.

To identify cellular sites of prolactin receptor messenger RNA synthesis in the rat brain, we used a combined reverse transcriptase-polymerase chain reaction protocol to generate single stranded DNA probes for in situ hybridization. The results of these experiments identify the epithelial cells of the choroid plexus as a major site of prolactin receptor gene expression in the rat central nervous system.

Animals↗
PubMed1992

Estrogenic regulation of heat shock protein 90 kDa in the rat ventromedial hypothalamus and uterus.

The regulation of heat shock protein 90 kDa (hsp90) by estradiol was analyzed in the rat ventromedial hypothalamus (VMH) and uterus by one-dimensional gel electrophoresis/Western blots. Protein from VMH and uterus (35 micrograms/sample) was resolved on 8% acrylamide gels, transferred to polyvinyldifluoride filters, and processed for immunoblotting using an anti-hsp90 antibody. Hsp90-specific bands were visualized on film using enhanced chemiluminescence and quantitated using a laser scanning densitometer. Hsp90 protein levels were significantly elevated in VMH at 12 h (p less than 0.01), and in uterus at 18 h (p less than 0.05) following estradiol injection (10 micrograms, s.c.). Immunocytochemical analysis for hsp90 localization by cell types showed that, in brain, hsp90 immunoreactivity was primarily neuronal. In the uterus, hsp90 immunoreactivity was most evident following treatment with estradiol, and was found primarily in the glandular epithelia; staining was less prominent in myometrium, stroma, and in the luminal epithelium. Thus, increased hsp90 levels may mediate some cellular responses to estrogen in specific cell types in both uterus and brain.

Animals↗
PubMed1992

Role of local environmental factors in determining tissue-specific effects of estrogen: examination of uterine tissues transplanted to brain.

Estrogen stimulates uterine epithelial cells to divide, but not estrogen-concentrating neurons in the adult brain. This effect correlates with recent evidence that estrogen can induce the expression of certain growth-related genes in uterus which are not directly induced by estrogen in the adult brain. The possibility that local diffusible factors play a major role in determining tissue-specific effects of estrogen was examined by transplanting uterine tissues into the brain, muscle and kidney of adult rats and then comparing the effects of estrogen on the incorporation of [3H]thymidine and the expression of Fos-, cdc2- and Rb-like immunoreactivity (IR) on native and transplanted uterine tissues, as well as in estrogen-concentrating regions of the brain adjacent to the uterine grafts. In native uteri, estrogen treatment stimulated Fos-, cdc2-, and Rb-like IR, as well as [3H]thymidine incorporation, within lumenal and glandular epithelial cells. All of these effects were estrogen responsive--no immunoreactive staining within uterine epithelial cells and no signs of epithelial cell proliferation were observed in the native uteri of non-estrogen-treated animals. When uterine tissues were transplanted to brain, Fos-, cdc2-, and Rb-like IR epithelial cells, as well as many [3H]thymidine-incorporating uterine epithelial cells, were observed in all estrogen-treated animals and in some non-estrogen-treated animals as well. Identical results were obtained when uterine tissues were transplanted to skeletal muscle, but not to kidney (in the kidney, transplanted epithelial cells expressed all four parameters but only in estrogen-treated animals, comparable to the native uterus). In contrast, estrogen did not stimulate cell division and did not induce Fos-, cdc2-, or Rb-like IR within estrogen-concentrating neuronal regions of the ventromedial hypothalamus. In addition, the presence of uterine tissue in the brain did not confer the ability of estrogen to stimulate any of these parameters within nearby, estrogen-concentrating regions. These data suggest that there are factors in brain and muscle which can allow uterine epithelial cells to divide in the absence of estrogen. There was no evidence of a diffusible factor in brain which inhibits uterine epithelial cell division, nor of a diffusible factor in uterus which can confer estrogenic stimulation of growth-related genes and cell division to central nervous system neurons. In addition, the data provide the first evidence for estrogen regulation of cdc2 and Rb expression in normal uterus.

Animals↗
PubMed1992

Electron microscopic identification of luteinizing hormone-releasing hormone-immunoreactive neurons in the medial olfactory placode and basal forebrain of embryonic mice.

Luteinizing hormone-releasing hormone is a decapeptide found in the brain and nose of all vertebrates that have been examined by immunocytochemical procedures with antiserum to luteinizing hormone-releasing hormone. It regulates the release of both luteinizing hormone and follicle-stimulating hormone from the gonadotropes of the anterior pituitary gland and promotes mating behavior. After about 11 days of embryogenesis in mice, luteinizing hormone-releasing hormone-immunoreactive cells are detected by immunocytochemical procedures in the medial olfactory placode, in the primordium of the vomeronasal organ. As they leave the olfactory placode, they run under the epithelial layer of the nasal septum associated with vomeronasal and terminalis nerves. Clustered, they stream toward the primordium of the olfactory bulb, passing along its ventromedial surface. Eventually, the largest numbers reach the septal and preoptic areas of the brain. Electron microscopic immunocytochemistry showed that luteinizing hormone-releasing hormone-immunoreactive product is accumulated just outside the nuclear envelope and in the lumen of rough endoplasmic reticulum adjacent to the cell nucleus of cells in and adjacent to the olfactory placode. As luteinizing hormone-releasing hormone-immunoreactive neurons migrate, they assume a fusiform shape and the immunoreaction product extends from the area around the nucleus throughout the cytoplasm, notably in processes which extend toward the direction of migration. Before and during migration, luteinizing hormone-releasing hormone was not detected in the Golgi apparatus or neurosecretory granules. It is inferred that as far as ultrastructural evidence is concerned, these neurons do not have a secretory function before they attain their target organs.

Animals↗
PubMed1992

LHRH neurons: functions and development.

Examination of the properties of developing LHRH neurons, by in situ hybridization procedures or LHRH immunocytochemistry, showed that these cells (1) are unique among neuroendocrine cells in their origin from the epithelium of the medial olfactory pit, and (2) express LHRH mRNA. LHRH neurons, visualized by either method, tended to be clustered when seen along the migration route in the nasal mesenchyme. Neural cell adhesion molecule (NCAM) is present on the central processes of the olfactory, vomeronasal and terminalis nerves, which form the scaffold along which LHRH neurons migrate into the brain. Injection of a small amount (1 microliter) of antiserum to NCAM into the olfactory pits of 10-day-old embryonic mice, while not sufficient to break up the NCAM scaffolding, appeared to decrease the number of LHRH-immunoreactive cells in the epithelium of the medial olfactory pit, and retarded their migration in the nasal mesenchyme. This suggest that NCAM is important for LHRH cell migration. Never found actually colocalized with LHRH in the same neurons, NCAM nevertheless may be required for the migration of LHRH-expressing cells.

Adult↗
PubMed1992

Immunocytochemical study of GnRH and GnRH-associated peptide in male Syrian hamsters as a function of photoperiod and gonadal alterations.

Hypothalamic luteinizing-hormone-releasing hormone (GnRH) and gonadotropin-releasing-hormone-associated peptide (GAP) biosynthesis and storage were estimated by immunocytochemistry in male golden hamsters maintained in different photoperiods. Intact or castrated male hamsters with subcutaneously inserted testosterone implants were exposed to long-day (14:10) or short-day photoperiods (10:14) for 4-8 weeks. Exposure to short photoperiod for 4 weeks, an interval characterized by a suppression of gonadotropin secretion but not gonadal regression, was associated with an increase in the number of GnRH- and GAP-immunoreactive cells in the diagonal band of Broca/medial septum. Furthermore, morphometric analysis revealed that these animals displayed significantly more GnRH but not GAP immunoreactivity in the median eminence as opposed to hamsters exposed to long-day photoperiods. In additional studies, gonadally regressed hamsters exposed to short day lengths for 8 weeks had equal numbers of GnRH cells as did the long-day controls. These patterns suggest that reproductive quiescence in golden hamsters is not the result of depletions of neuronal GnRH stores available for secretion.

Animals↗
PubMed1992

Steady state analysis of hypothalamic GnRH mRNA levels in male Syrian hamsters: influences of photoperiod and androgen.

An in situ hybridization assay, utilizing a free floating technique was used to estimate the steady state levels of hypothalamic luteinizing hormone-releasing hormone (GnRH) mRNA levels in the brains of male golden hamsters maintained in different photoperiods. In situ histochemistry was performed using a 32P-labelled 66-nucleotide long oligomer complementary to the sequence of the human GnRH mRNA coding region. The oligonucleotide hybridized specifically to mRNA encoding the GnRH precursor as suggested by the distribution of labelled neurons and as shown by an RNAse protection assay on septal and preoptic-hypothalamic mRNA from gonadally regressed hamsters. To test the hypothesis that short-day photoperiods reduce GnRH synthesis, intact male hamsters or castrated males bearing subcutaneously inserted testosterone implants were exposed to long-day (14 h light:10 h dark) or short-day (10 h light 14 h dark) photoperiods for 4 weeks. Exposure to short day lengths never caused a decrease in GnRH expressing neurons and actually was associated with an increase in the number of radiolabelled cells specifically in the diagonal band of Broca/medial septum in the gonadally intact group. The mean number of grains per labelled cell for the short day animals similarly was not reduced from that seen in long day animals. The results are consistent with previous studies on photoperiod and GnRH content in the same brain regions and support the notion that the suppression of the synthesis of GnRH does not accompany the low levels of LH secretion observed during the early stages of reproductive quiescence in this species.

Animals↗
PubMed1992

Electrophysiological analyses of serotonergic actions on neurons in hypothalamic ventromedial nucleus in vitro: receptor subtypes involved and implications for regulation of feeding and lordosis behaviors.

Previously, we have shown that serotonin (5-HT) can inhibit, excite, or biphasically inhibit and excite individual neurons of the ventromedial nucleus (VMN) in hypothalamic slices from female rats. In the present study, similar in vitro methods were used to further characterize VMN neurons responsive to 5-HT, and to identify the receptor subtypes involved in mediating these 5-HT actions. Results from a dose-response experiment indicate that increasing the dose of 5-HT can transform an inhibitory response into a biphasic or even an excitatory response. This indicates that modulation of 5-HT release in the VMN could alter the net response of the VMN to this transmitter. By comparing the actions of 5-HT with the effects of selective agonists and antagonists, the inhibitory action was found to be mediated predominantly, if not exclusively, by 5-HT1A receptors, while the excitatory action was mediated predominantly or exclusively through 5-HT2 receptors. There appear to be few, if any, 5-HT3 receptors in the VMN, and their functions are unclear. The inhibitory and the excitatory phases of the biphasic responses were not mediated together by a single receptor subtype but were mediated separately by 5-HT1A and 5-HT2 receptors, respectively. The presence of the biphasic response in a large proportion of neurons, therefore, indicates the coexistence of different subtypes of 5-HT receptors in many individual VMN neurons. The use of selective agonists and antagonists further indicates that the coexistence also occurs in neurons showing monophasic responses, and that the opposite actions mediated by the coexisting receptor subtypes can interact with each other. Therefore, changing the ratio of coexisting receptor subtypes could modify the net output of the VMN response to 5-HT. Together with behavioral studies by others, it emerges from our findings that the inhibitory action of 5-HT on VMN neurons is associated with, and may be responsible for, the stimulation of feeding and inhibition of lordosis, while the excitatory action is related and may lead to the opposite behavioral effects. Finally, with the coexistence in VMN neurons of two receptor subtypes that can mediate 5-HT effects on both feeding and lordosis, the VMN can serve as a substrate for 5-HT to coordinate these two behaviors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1991

Effects of daytime and nighttime stress on Fos-like immunoreactivity in the paraventricular nucleus of the hypothalamus, the habenula, and the posterior paraventricular nucleus of the thalamus.

Circadian effects on basal and stress-induced Fos-like immunoreactivity (IR) in the paraventricular nucleus of the hypothalamus (PVN), the habenula (Hab) and the posterior paraventricular nucleus of the thalamus (PVN-Thal) were examined. Stress induced a significant increase in the number of Fos-like IR cells within all 3 brain regions. In the Hab, expression was localized specifically to the medial region of the lateral Hab. No differences between the effects of daytime vs nighttime stress on numbers of Fos-like IR cells in the PVN and PVP-Thal were observed. Significantly fewer Fos-like IR cells were observed, however, in the lateral habenula of nighttime vs daytime non-stressed controls, resulting in a significantly greater percentage increase in Fos-like IR in the lateral habenula following nighttime vs daytime stress.

Animals↗
PubMed1991

Ovarian steroid modulation of [3H]muscimol binding in the spinal cord of the rat.

[3H]Muscimol binding was measured in the lumbar spinal cord of female rats by in vitro quantitative autoradiography. Ovariectomized rats were treated subcutaneously with either oil, estradiol benzoate (EB) or EB plus progesterone (P) in a regime known to reliably induce sexual receptivity. The level of [3H]muscimol binding was highest in laminae I-III and in the region around the central canal. Binding was lower in laminae IV-VI and was frequently undetectable in the ventral horn. There was a significant increase in the level of binding in laminae I-III after EB treatment. There was also a significant increase after treatment with EB+P in comparison to both the ovariectomized and EB-treated groups in this same region of the spinal cord.

Animals↗
PubMed1991

Estrogen influences on oxytocin mRNA expression in preoptic and anterior hypothalamic regions studied by in situ hybridization.

Possible estrogen influences on oxytocin mRNA expression were studied in preoptic and anterior hypothalamic regions as might be important for behavioral as well as neuroendocrine controls. In situ hybridization for oxytocin mRNA determination was supported by immunocytochemical identification and was compared with vasopressin mRNA in situ hybridization. With these techniques, oxytocin-expressing neurons were identified in medial preoptic, anterior commissural, periventricular, paraventricular, supraoptic, and perifornical nuclei as well as the bed nucleus of the stria terminalis and intersupraopticoparaventricular (internuclear) islands. Distribution and number of oxytocin mRNA-containing neurons and oxytocin mRNA levels were compared between ovariectomized control rats given cholesterol implants and ovariectomized rats given short-term (2 days) or long-term (2 months) estradiol treatment (10% estradiol, subcutaneous silastic implants). Effectiveness of long-term estrogen treatment was confirmed behaviorally. While there was a trend in several cell groups for a larger number of oxytocin-mRNA-containing neurons to be observed following 2 days of estrogen treatment, this was not statistically significant. Moreover, additional oxytocin-mRNA containing cell groups were not seen after short or long estradiol treatment. With computer-aided analysis, mean pixels per oxytocin-mRNA expressing neuron (reflecting oxytocin mRNA content) were compared between groups: In the supraoptic nucleus and the anterior commissural nucleus, these were increased both by 2 days and 2 months of estradiol treatment. These differences may be important in modulating female reproductive behavior. Present findings also suggest that estradiol can affect the oxytocinergic system via an indirect route since the cell groups influenced here by estradiol do not contain estrogen receptors. Oxytocinergic neurons may serve as a good system to compare direct transcriptional with indirect effects of hormones.

Animals↗
PubMed1991

Effects of gamma-aminobutyric acid receptor agonists and antagonist on LHRH-synthesizing neurons as detected by immunocytochemistry and in situ hybridization.

Gamma-aminobutyric acid (GABA) is thought to play an important role in the regulation of luteinizing hormone-releasing hormone (LHRH) release but its role in the regulation of LHRH gene expression and LHRH synthesis is not known. We hypothesized that since GABA appears to have primarily inhibitory effects on LHRH cells (at the level of the cell body), GABA may act to decrease LHRH gene expression and peptide synthesis. This hypothesis was tested by examining the effect of GABA receptor activation and GABA receptor blockade on LHRH mRNA and peptide levels employing in situ hybridization and immunocytochemistry. Cells in the preoptic area (POA) of ovariectomized (ovx) rats were selectively exposed in vivo to specific GABA-ergic receptor agonists or an antagonist for up to 24 h. THIP, a specific GABAA receptor agonist, did not have a significant effect on either the intensity of LHRH immunoreactivity, or the number of LHRH-ir cells, observed as compared to controls. Baclofen, a GABAB receptor agonist appeared to decrease the number of cells with the greatest intensity of LHRH immunoreactivity, compared to controls. In situ hybridization, with either a tritiated RNA probe or a 32P-labelled oligonucleotide, complementary to LHRH mRNA, revealed that THIP either had no effect on the labelling intensity (32P-labelled oligonucleotide) or (contrary to our hypothesis) a slight excitatory effect on the level of LHRH mRNA detected per cell (tritiated RNA probe). Bicuculline (a specific GABAA receptor antagonist) decreased both the number of labelled cells observed per section through the POA, and the intensity of labelling observed in sections hybridized with the 32P-labelled oligonucleotide. These results suggest that in the POA GABAA receptors do not exert an inhibitory effect on LHRH gene expression, but rather could affect LH perhaps by electrically inhibiting LHRH neurons. In contrast, baclofen appeared to exert an inhibitory effect on LHRH gene expression, since the number of grains per labelled cell in the POA of baclofen-treated rats was lower than the grains per labelled cell of control rats. Also, similar to the results obtained with immunocytochemistry, in situ hybridization following baclofen treatment suggested that activation of GABAB receptors is able to reduce the number of neurons with the highest levels of LHRH mRNA. Thus, in the POA, GABA acting through GABAB receptors could be effective through changes in mRNA or peptide synthesis.

Animals↗
PubMed1991

Effects of GABA and related agents on the electrical activity of hypothalamic ventromedial nucleus neurons in vitro.

Functional and neurochemical evidence suggests significant GABA participation in the basomedial hypothalamus. We have investigated electrophysiological effects of GABA using in vitro recording from hypothalamic tissue slices. Exogenous GABA inhibited 94 out of 121 ventromedial hypothalamic (VMN) neurons tested. In sixty-one percent of these GABA-responsive neurons, the inhibitory action of GABA was blocked by GABAA antagonists, bicuculline methiodide (BMI) and picrotoxin (PTX). Nevertheless, many (27/69) GABA-responsive neurons were not sensitive to GABAA blockers: BMI and PTX failed to antagonize inhibitory action of GABA. Most, if not all, of these inhibitions can be accounted for by GABAB effects, since baclofen powerfully inhibited 42 of 44 neurons tested. In addition to blocking the inhibitory action of exogenous GABA, BMI (55%) and PTX (36%) also caused changes of neuronal activity indicating blockade of intrinsic GABAergic action. Altogether, our results showed that, in the VMN, GABA acts through not only GABAA but also GABAB receptors to inhibit neuronal activity, and that there is tonic inhibition by intrinsic GABA neurons. These GABA actions may participate in behaviorally-relevant VMN hypothalamic mechanisms.

Animals↗
PubMed1991

Midbrain central gray GABAA receptor activation enhances, and blockade reduces, sexual behavior in the female rat.

The inhibitory neurotransmitter, GABA, has been implicated in the control of lordosis behavior. Previous studies indicate that modulation of GABAA transmission can have dual effects on lordosis, being facilitative in the ventromedial hypothalamus and inhibitory in the preoptic area. The midbrain central gray (MCG) is also known to be an important neural site for regulating lordosis as well as defensive and escape behaviors, and plays an integral role in the control of nociception. Because of the multitude of behaviors regulated at the level of the MCG, we utilized a two-chamber testing apparatus that allowed simultaneous measurement of the females' proceptive (hopping and darting), receptive and rejection behaviors, as well as an index of nociception and general motor activity. We found that microinfusion of the GABAA antagonist, bicuculline, into the MCG of steroid-primed female rats resulted in a significant decrease in lordosis and proceptive behaviors at 5 min post-infusion. There was full recovery to pretest levels by 60 min. Furthermore, microinfusion of the GABAA agonist, muscimol, to estrogen-treated females that displayed low levels of receptivity and high levels of rejection behavior during a pretest, resulted in a significant increase in lordosis responding and a decrease in rejection behaviors. Neither drug significantly affected time spent in the vicinity of the male, motor activity or vocalizations. It is concluded that the decrease in lordosis resulting from blockade of GABA transmission is not solely due to the induction of antagonistic behaviors since there was no increase in rejections after bicuculline administration. The current findings are consistent with the interpretation that GABA facilitates lordosis in the MCG via disinhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The effects of the TRH metabolite cyclo(His-Pro) and its analogs on feeding.

Cyclo(His-Pro), or cHP, is a putative metabolite of thyrotropin-releasing hormone (TRH), and, like TRH, can inhibit food intake but requires higher doses. In attempts to improve the anorectic effects of cHP through modification of its structure, a number of its analogs were synthesized. These analogs or cHP itself were administered to rats either by intracerebroventricular (ICV) infusion or systemic injection, and their effects on food intake were measured. None of the synthetic analogs was more potent than cHP, although several analogs demonstrated comparable potencies to the parent compound. Interestingly, one cHP analog reversed the suppressive effect and stimulated feeding. This reversal, as well as the preservation of the anorectic effect by some but not all the analogs, suggests that the cHP effect on feeding does require specific structural features.

Animals↗
PubMed1991

Cyclo(His-Pro) potentiates the reduction of food intake induced by amphetamine, fenfluramine, or serotonin.

Electrophysiological and pharmacological evidence suggests that cyclo(His-Pro) (cHP) could reduce food intake by modulating the actions of relevant neurotransmitters. We tested this hypothesis by giving rats a combination of cHP or its analogs centrally and an anorectic, amphetamine or fenfluramine, systemically. Compared to saline control, cHP at doses too low to affect food intake by itself significantly potentiated the reduction of food intake by amphetamine. This potentiation is thought to be due to cHP modulation of norepinephrine (NE) action, because at the low dose used amphetamine acts mainly through NE to inhibit food intake. The modulation has specific requirements for cHP structure, since it was mimicked by one but not two other analogs tested. The anorectic effect of fenfluramine was also potentiated and prolonged by cHP at a dose not effective by itself. Since fenfluramine is known to act by increasing brain serotonin (5-HT), the potentiation was apparently a result of an interaction between cHP and 5-HT effects. To examine this interaction more directly, we administered both cHP and 5-HT centrally. Again, cHP potentiated the reduction of food intake caused by 5-HT. Thus the neuromodulation of feeding-relevant neurotransmitter effects, following NE and 5-HT, is probably a mechanism by which cHP reduces food intake.

Animals↗