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PubMed1981

The influence of gonadectomy, androgen exposure, or a gonadal graft in the neonatal rat on the volume of the sexually dimorphic nucleus of the preoptic area.

Although the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of the adult rat has been shown to be modified by the hormone environment early in postnatal life, the present study was performed to clarify several fundamental questions related to this process. This study was designed to evaluate the ability of exogenous testosterone propionate (TP), or a gonadal graft, to influence SDN-POA volume in rats which were gonadectomized as neonates. Orchidectomy on day 1 resulted in an approximately 50% decrease in adult SDN-POA volume; however, the influence of the testes on their resulting SDN-POA volume was replaced affectively by the administration of 100 micrograms or 1 mg of TP on postnatal day 2 or by a testicular (but not ovarian) graft on the day of castration. In the female, ovariectomy on postnatal day 1 failed to alter SDN-POA volume relative to that of sham-operated females. Exogenous TP, but neither testicular nor ovarian grafts, resulted in a larger SDN-POA volume when observed in the adult female. Thus, the development of the SDN-POA of the neonatal male is significantly influenced by the hormonal activity of the testes at this time period. While the SDN-POA of the neonatal female is potentially responsive to androgen, the role played by the ovaries in the development of the SDN-POA remains unclear. In addition, the different response of the developing male and female SDN-POA to a testicular graft suggests that the hormonal sensitivity of this nucleus may differ in the two sexes.

Animals↗
PubMed1990

Dorsolateral connections of the medial preoptic area and maternal behavior in rats.

The lateral connections of the medial preoptic area (MPOA) are essential for maternal behavior in rats. The purpose of this study was to more exactly specify the nature of this pathway. Experiment 1 found that knife cuts that severed the dorsolateral connections of the MPOA were as effective as complete cuts in disrupting maternal behavior, whereas knife cuts that severed the ventrolateral MPOA connections were ineffective. These results suggest that MPOA efferents and afferents critical for maternal behavior leave or enter the MPOA dorsolaterally. Experiment 2 located possible sources of critical afferent input. Lactating rats received MPOA lateral cuts with a horseradish peroxidase (HRP)-coated wire knife. Full lateral cuts and dorsolateral cuts disrupted maternal behavior and labeled more cells with HRP in the nucleus of the solitary tract and the locus coeruleus than did ventrolateral cuts, which did not disrupt maternal behavior.

Animals↗
PubMed2002

Neuronal inputs from the hypothalamus and brain stem to the medial preoptic area of the ram: neurochemical correlates and comparison to the ewe.

The retrograde tracer, FluoroGold, was used to trace the neuronal inputs from the septum, hypothalamus, and brain stem to the region of the GnRH neurons in the rostral preoptic area of the ram and to compare these imputs with those in the ewe. Sex differences were found in the number of retrogradely labeled cells in the dorsomedial and ventromedial nuclei. Retrogradely labeled cells were also observed in the lateral septum, preoptic area, organum vasculosum of the lamina terminalis, bed nucleus of the stria terminalis, stria terminalis, subfornical organ, periventricular nucleus, anterior hypothalamic area, lateral hypothalamus, arcuate nucleus, and posterior hypothalamus. These sex differences may partially explain sex differences in how GnRH secretion is regulated. Fluorescence immunohistochemistry was used to determine the neurochemical identity of some of these cells in the ram. Very few tyrosine hydroxylase-containing neurons in the A14 group (<1%), ACTH-containing neurons (<1%), and neuropeptide Y-containing neurons (1-5%) in the arcuate nucleus contained FluoroGold. The ventrolateral medulla and parabrachial nucleus contained the main populations of FluoroGold-containing neurons in the brain stem. Retrogradely labeled neurons were also observed in the nucleus of the solitary tract, dorsal raphe nucleus, and periaqueductal gray matter. Virtually all FluoroGold-containing cells in the ventrolateral medulla and about half of these cells in the nucleus of the solitary tract also stained for dopamine beta-hydroxylase. No other retrogradely labeled cells in the brain stem were noradrenergic. Although dopamine, beta-endorphin, and neuropeptide Y have been implicated in the regulation of GnRH secretion in males, it is unlikely that these neurotransmitters regulate GnRH secretion via direct inputs to GnRH neurons.

Adrenocorticotropic Hormone↗
PubMed1992

Estradiol plus progesterone promote glutamate-induced release of gamma-aminobutyric acid from preoptic area synaptosomes.

Treatment of ovariectomized rats with both estradiol and progesterone in vivo resulted in a marked enhancement of glutamate-induced release of newly synthesized [3H]gamma-aminobutyric acid (GABA) from synaptosomes of the preoptic area in vitro. With this treatment, as little as 0.01 nM glutamate, in vitro, enhanced release of GABA. In contrast, glutamate, in vitro, did not stimulate release of GABA from synaptosomes, obtained from rats treated with either estradiol or progesterone alone and only large concentrations of glutamate (1.0 and 10 mM) caused a modest release of GABA from synaptosomes from ovariectomized, vehicle-treated rats. Also, treatment with estradiol plus progesterone did not alter glutamate-induced release or exchange of [3H]glutamate. Glutamate-induced release of GABA was calcium-independent and attenuated by the putative chloride channel antagonist, 4,4'-diisothiocyanatostilbene-2,2'-DL-disulfonic acid. Thus, glutamate-induced, steroid-enhanced release of GABA may occur through a chloride-dependent carrier rather than by exocytosis. In addition to enhancement by glutamate, release of GABA was also enhanced by D-aspartate, an agent that is transported by the neuronal glutamate carrier. It is postulated that enhancement of glutamate-induced release of GABA, by estradiol plus progesterone in the preoptic area, represents one process by which these steroids modulate reproductive function in female rats.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1993

Hyperthermia induces c-fos expression in the preoptic area.

To identify thermosensitive areas of brain, we exposed rats to warm or cool environments and used the expression of the protein Fos as a marker of neuronal activity. In hyperthermic, heat-exposed rats, the median preoptic nucleus, and the medial and lateral preoptic areas had significantly more Fos immunoreactive neurons than control or cold-exposed animals. These observations add to the physiologic evidence that neurons of the preoptic area participate in thermoregulation and provide a means to identify the neurotransmitter systems involved.

Animals↗
PubMed1987

Lateralized functional relationship between the preoptic area and lateral hypothalamic reinforcement.

Electrical self-stimulation in the lateral hypothalamus of both hemispheres was recorded in 14 rats before and after administration of a unilateral ibotenic acid lesion of the cell bodies in the region of the lateral preoptic area. A significant decrease in the rate of self-stimulation at each of two stimulation intensities was found when the electrode was placed in the hemisphere in which the ibotenic acid lesion was made. This decrease remained constant over 21 days of testing. No changes were detected in rate of self-stimulation in the intact contralateral hemisphere. These results provide evidence for a role in lateral hypothalamic self-stimulation of intrinsic neurons located in the region of the lateral preoptic area.

Animals↗
PubMed1999

Identification and characterization of estrogen receptor alpha-containing neurons projecting to the vicinity of the gonadotropin-releasing hormone perikarya in the rostral preoptic area of the rat.

Gonadal steroids exert a powerful regulatory influence upon the functioning of gonadotropin-releasing hormone (GnRH) neurons despite the apparent absence of gonadal steroid receptors in these cells. By using retrograde-tracing techniques combined with dual-labeling immunocytochemistry, we show here that distinct populations of estrogen receptor alpha (ERalpha)-containing neurons located in the hypothalamus and caudal brainstem project to the vicinity of the GnRH perikarya located in the rostral preoptic area (rPOA). The strongest estrogen-receptive afferent projection to this area originated from neurons located in the anteroventral periventricular and medial preoptic nuclei of the preoptic area. Approximately 50% of arcuate nucleus neurons projecting to the rPOA were demonstrated to synthesize either neuropeptide Y or beta-endorphin, but little evidence was found for ERalpha immunoreactivity in either of these specific subpopulations. Over 80% of all tyrosine hydroxylase-expressing neurons in the arcuate nucleus expressed ERalpha, but none projected to the rPOA. In the caudal brainstem, the A1 and A2 norepinephrine neurons comprised nearly all of the retrogradely labeled neurons. However, only the A2 afferents expressed ERalpha immunoreactivity, whereas the A1 afferents coexpressed neuropeptide Y. These observations, combined with the anterograde labeling data of others, provide neuroanatomical evidence for the existence of specific estrogen-receptive neuronal cell populations that project to the rPOA and may be involved in the estrogen-dependent transsynaptic regulation of GnRH neurons in the rat.

Afferent Pathways↗
PubMed1971

Sexual dimorphism in the preoptic area of the rat.

A quantitative evaluation of the relative distribution of synapses on dendritic shafts and spines serves to differentiate the neuropil of the preoptic area from that of the ventromedial hypothalamic nucleus; it also shows that the neuropil of the preoptic area is sexually dimorphic.

Amygdala↗
PubMed1994

Effect of carbachol injection in the medial preoptic area on sleep-wakefulness and body temperature in free moving rats.

The aim of the present study was to find out the changes in sleep-wakefulness and body temperature brought about by application of cholinergic agonist, carbachol, in the medial preoptic area (mPOA). Carbachol, when injected bilaterally into the mPOA of male rats, through chronically implanted cannulae, produced a fall in rectal temperature and long lasting arousal. There was temporal dissociation in the duration of changes produced in the two parameters. It is suggested that the cholinergic system at the medial preoptic area brings about arousal response and fall in body temperature through different circuits.

Analysis of Variance↗
PubMed1985

Sexually dimorphic regions in the medial preoptic area and the bed nucleus of the stria terminalis of the guinea pig brain: a description and an investigation of their relationship to gonadal steroids in adulthood.

Sexually dimorphic regions are described in two areas of the guinea pig brain: the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST). The volume of a darkly staining portion of the MPOA is approximately 4-fold larger in male than in female guinea pigs, and the volume of a darkly staining portion of the BNST is approximately 36% larger in male than in female animals. The sex differences in both of these areas are present in animals that have been gonadectomized as adults as well as in intact animals, suggesting that they result from differences between the sexes in the hormonal environment during early development. Both the MPOA and the BNST bind high levels of gonadal steroids early in life, during the period when functional differentiation occurs. It is possible that dramatic morphological sex differences characterize such steroid-binding areas. Furthermore, these sexually dimorphic areas may form an anatomically and functionally interrelated system. Attention to these possibilities may help elucidate more precisely the neural basis for sexually dimorphic functions, as well as the basic mechanisms underlying sexual differentiation of behavior and the brain.

Animals↗
PubMed1995

Branching serotonergic and non-serotonergic projections from caudal brainstem to the medial preoptic area and the lumbar spinal cord, in the rat.

The distribution and the chemical identity of retrogradely single and double labeled neurons in the caudal raphe nuclei were analyzed in the rat following injection of two fluorescent tracers into the medial preoptic area and the ventral/intermediate grey of the lumbar spinal cord, and serotonin immunocytochemistry. The results suggest that (1) neurons in the caudal raphe nuclei exhibit highly collateralized axons, able to simultaneously innervate rostrally- and caudally-located targets; (2) a large proportion (40-50%) of the raphe-spinal projection does not contain serotonin, which by contrast is present in more than 70% of the neurons projecting to the medial preoptic area; (3) only a small fraction of the observed collateralized projection is serotonergic. Thus, multiple transmitter systems are likely to be involved in the diffuse ascending and descending influence arising from these nuclei.

Animals↗
PubMed1979

Neural connexions between the medial forebrain bundle, the preoptic area and the basal hypothalamus in the rat: an electrophysiological study.

1. Electrophysiological experiments have been performed on intact cycling female rats to investigate the neural connexions that exist between the medial forebrain bundle, the anterior hypothalamic region, which included the preoptic area, and the basal hypothalamus. Recordings have been made from a total of 351 neurones in the anterior hypothalamus of which 216 were responsive to stimulation of either or both the medial forebrain bundle and basal hypothalamus (arcuate and ventromedial nuclei).2. Forty-six of these cells were responsive to a stimulus applied both to the medial forebrain bundle and the basal hypothalamus with a variety of response combinations. The majority of neurones were orthodromically activated by stimulation in both sites. Inhibition by stimulation of the medial forebrain bundle coupled with orthodromic excitation from the basal hypothalamus, or the reverse situation, was also encountered frequently.3. A few cells were antidromically invaded by the stimulation of the medial forebrain bundle and these received orthodromic or inhibitory inputs from the basal hypothalamus, although one unit outside the anterior hypothalamus was antidromically activated by both stimuli.4. Ninety per cent of all the doubly responsive units that could be antidromically activated by stimulation of the basal hypothalamus received an orthodromic input from the medial forebrain bundle, and no cells in the anterior hypothalamus that projected to the basal hypothalamus were found to receive an inhibitory input from the medial forebrain bundle.5. These results provide electrophysiological evidence for inhibitory and excitatory inputs from the medial forebrain bundle to the preoptic and anterior hypothalamic cells that either project to, or receive connexions from, the basal hypothalamus. Neurones in the preoptic area which project to the basal hypothalamus are implicated in the control of anterior pituitary function, particularly gonadotrophin secretion. These experiments, coupled with functional studies, suggest that there is an excitatory input from the medial forebrain bundle to these preoptic and anterior hypothalamic cells which may modulate adenohypophyseal secretions.

Animals↗
PubMed1999

Mating-induced Fos and aromatase are not co-localized in the preoptic area.

Male sexual behavior is determined by the interaction of endocrine and environmental stimuli originating from the female, yet it is unknown how and where these stimuli are integrated within the brain. Activation of copulatory behavior by testosterone is limited by its central aromatization into an estrogen in the preoptic area. We investigated whether mating-induced neuronal activation as identified by the expression of the immediate early gene Fos occurs in aromatase-immunoreactive (ARO-ir) cells of the male quail preoptic area. Fos-immunoreactive (ir) cells were observed within and lateral to these ARO-ir cells groups but few ARO-ir cells contained Fos-ir indicating that mating-related stimuli do not directly affect estrogen-synthesizing cells.

Animals↗
PubMed1989

Alpha-adrenergic regulation of androgen receptor concentration in the preoptic area of the rat.

We examined the effect of the pharmacological disruption of the catecholaminergic system on the concentration of nuclear androgen receptor, as measured by the in vitro binding of methyltrienolone ([3H]R1881) to salt extracts of anterior pituitary (AP), preoptic area (POA) and medial basal hypothalamus (MBH). Treatment of gonadectomized male and female rats with the dopamine-beta-hydroxylase inhibitor, diethyldithiocarbamate (400 mg/kg b. wt.), 30 min before treatment with dihydrotestosterone (1 mg/animal) produced a decrease in the number of nuclear androgen receptor compared with saline-treated controls (P less than 0.05). This effect was specific for the POA and was not present 15 h after DHT treatment. There was no effect on cytosolic androgen receptor nor was there a drug effect on the apparent dissociation constant (Kd) of [3H]R1881 binding to hypothalamus-preoptic area cytosols. Treatment of intact males and castrated, testosterone-treated males with the alpha 1- and alpha 2-adrenergic antagonists, prazosin (5 mg/kg b. wt.) and yohimbine (2 mg/kg b. wt.), respectively, resulted in a significant decrease in the number of nuclear AR 2 h following drug treatment (P less than 0.05). There was no effect of the beta-adrenergic receptor antagonist propranolol (10 mg/kg b. wt.) when given to intact animals, nor was there an effect of idazoxan (5 mg/kg) when given to testosterone-treated animals. The effects of yohimbine and prazosin were restricted to the POA. None of the drugs competed with the binding of [3H]R1881 for the androgen receptor nor did they alter the Kd of cytosol or nuclear androgen receptor. These data provide evidence for an adrenergic interaction with the POA androgen receptor and suggest a role for catecholamines in modulating androgen sensitivity in the rat brain.

Adrenergic Fibers↗
PubMed2003

Estrogen receptor alpha expression in the medial preoptic area and the medial basal hypothalamus under different physiological conditions in cattle.

The distribution and morphology of immunoreactive estrogen receptor alpha (ERalpha)- containing cells were examined in the cattle brain. The brains were collected from two cows and a male calf. One of the cows was sacrificed one week after parturition. ERalpha expressions in the preoptic area of the rostral forebrain and the medial basal hypothalamic area were evaluated immunohistochemically using a mouse monoclonal antibody. In all animals, the signals that indicate ERalpha were detected in the medial preoptic area, the level of the organum vasculosum of the lamina terminalis and the bed nucleus of the stria terminalis. In the caudal hypothalamic region, they were detected in the arcuate nucleus, the periventricular and ventromedial hypothalamic nuclei. ERalpha-containing cells were characterized by a dense nuclear reaction product. In all the subjects examined, ERalpha signals were clearly detected in the cytoplasm as well. The density of ERalpha expression was different among the three cattle; the number of ERalpha containing cells in the postpartum cow was much lower than that in the other cow and the male calf. The present findings suggest that ERalpha expression in the forebrain is influenced by the reproductive status in the cattle.

Animals↗
PubMed1985

Evidence that prostaglandins within preoptic area (POA) may mediate the antidipsogenic effect of Escherichia coli endotoxin in the rat.

Intravenous injection of Escherichia coli endotoxin (LPS; 640 micrograms/kg) produced an antidipsogenic effect in 48-h water-deprived rats, which was antagonized by acetylsalicylic acid (ASA; 0.45, 0.9 microM) injected directly into cerebral preoptic area (POA). ASA (0.9 microM) when injected into POA did not elicit, by itself, any effect on drinking. Endotoxin (0.5, 1, and 2 micrograms), when injected directly into POA, produced a dose-dependent inhibition of drinking stimulated by water deprivation. This effect was antagonized by ASA (0.45 microM) injected into POA 15 min before LPS. Injection of LPS (2 micrograms) into brain areas not involved in drinking regulation (superior colliculus or nucleus caudatus) was without effect on 48-h water deprivation-induced thirst. PGI2 (5, 50, and 500 ng) injected ino POA showed a dose-dependent antidipsogenic effect on drinking stimulated by water deprivation. The data suggest that prostaglandins, within the preoptic area, might be involved in the antidipsogenic effect of E coli LPS, given either intravenously or directly into POA.

Animals↗
PubMed1990

Neurons containing messenger RNA encoding glutamate decarboxylase in rat hypothalamus demonstrated by in situ hybridization, with special emphasis on cell groups in medial preoptic area, anterior hypothalamic area and dorsomedial hypothalamic nucleus.

Previous deafferentation studies have suggested that most hypothalamic GABAergic innervation originates from neurons within the hypothalamus. We have investigated the distribution of GABAergic cell groups in the rat hypothalamus by means of the in situ hybridization technique, using a cDNA probe for messenger RNA encoding glutamate decarboxylase. Several major GABAergic cell groups were demonstrated, including cells of the tuberomammillary nucleus, arcuate nucleus, suprachiasmatic nucleus, medial preoptic area, anterior hypothalamic area, the dorsomedial hypothalamic nucleus, perifornical area, and lateral hypothalamic area. The most prominent glutamate decarboxylase mRNA-containing cell groups were located in the medial preoptic area, anterior hypothalamic area and dorsomedial hypothalamic nucleus, and were composed of small- to medium-sized neurons. Compared to previously well-characterized GABAergic cell groups in the tuberomammillary nucleus, reticular thalamic nucleus, and non-pyramidal cells of cerebral cortex, the cells of these GABAergic groups demonstrated only weak cDNA labelling, indicating that they contain lower levels of glutamate decarboxylase mRNA. Several types of control experiments supported the specificity of this cDNA labelling, and the GABAergic nature of these cell populations was further supported by detection of glutamate decarboxylase and GABA immunoreactivity. Abundance of GABAergic cells in many hypothalamic nuclei indicates that GABA represents quantitatively the most important transmitter of hypothalamic neurons, and may be involved in neuroendocrine and autonomic regulatory functions.

Animals↗
PubMed2004

Glutamic acid decarboxylase 67 (GAD67) gene expression in discrete regions of the rostral preoptic area change during the oestrous cycle and with age.

Gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, is important to the timing and amplitude of the gonadotrophin-releasing hormone (GnRH)-induced luteinizing hormone (LH) surge on pro-oestrus. Data suggest that GABA input in the preoptic area must decrease for a normal LH surge to occur in young rats. We have previously found that ageing alters the timing and amplitude of the LH surge. Therefore, this study focused on changes in GAD(67) gene expression, a reflection of GABA synthesis, in two regions of the rostral preoptic area, the organum vasculosum of the lamina terminalis (OVLT) and the anteroventral periventricular nucleus (AVPV) during the oestrous cycle and with age. We assessed the possibility that the expression of GAD(67) mRNA in these regions displays time-related and age-dependent changes on pro-oestrus. Our results demonstrate that, with age, overall expression of GAD(67) mRNA decreases in the area surrounding the OVLT and in the AVPV. Young rats display a diurnal rhythm in GAD(67) mRNA in both regions. GAD(67) mRNA expression is high during the early morning hours of pro-oestrus and then declines around the time of the GnRH-induced LH surge. In addition, the diurnal rhythm disappears in the AVPV and is attenuated in the area surrounding the OVLT of middle-aged proestrous rats. These findings suggest that a loss of rhythmicity in GAD(67) gene expression and maintenance of inhibitory tone on proestrous afternoon may alter the timing and amplitude of the LH surge, as previously observed in middle-aged rats.

Aging↗