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PubMed1994

Estrogen-inducible neurotensin immunoreactivity in the preoptic area of the female rat.

Neurotensin (NT) neurons in the rat preoptic area are implicated in female-specific regulation of reproduction. Estrogen markedly increases expression of mRNA encoding the neurotensin/neuromedin N (NT/N) precursor in several cell groups of the preoptic area, including the anteroventral periventricular nucleus, periventricular preoptic nucleus, and medial preoptic nucleus. In the present study, immunohistochemistry was performed on tissue from ovariectomized females with or without estradiol treatment to test the hypothesis that increased levels of NT accompany hormonal induction of NT/N mRNA in these cell group. Since colchicine treatment is required for visualization of NT-immunoreactive cell bodies, an additional objective of this study was to determine whether colchicine alters expression of NT/N mRNA in this area. Estradiol caused a pronounced increase in the number of NT-immunoreactive cell bodies in the anteroventral periventricular nucleus, as well as adjacent parts of the periventricular preoptic nucleus and medial preoptic nucleus. In the absence of colchicine, estradiol increased the number of NT-immunoreactive fibers in these same regions. Surprisingly, NT-immunoreactive cell bodies with intense staining were abundant in certain parts of the medial preoptic nucleus regardless of hormonal condition. NT-immunoreactive cell bodies were also numerous in certain regions where NT/N mRNA-expressing cells are scarce, and in two of these regions, the median preoptic nucleus and vascular organ of the lamina terminalis, estradiol substantially reduced the number of immunoreactive cell bodies. Treatment of ovariectomized females with colchicine induced expression of NT/N mRNA in the same regions where NT-immunoreactive cell bodies were unexpectedly numerous, thus providing a compelling explanation for the discordant distributions of the mRNA and peptide. Together with previous findings, the present results indicate that increased levels of NT accompany hormonal induction of NT/N mRNA in the anteroventral periventricular nucleus, as well as adjacent parts of the periventricular preoptic nucleus and medial preoptic nucleus. In other regions of the preoptic area, colchicine-inducible expression of NT/N mRNA confounds assessment of hormonal influences on NT synthesis. Multiple populations of neurons capable of NT synthesis can be distinguished in the rostral preoptic area on the basis of differential responsiveness to estrogen or colchicine, thereby providing additional evidence for functional heterogeneity among NT-synthesizing neurons in this region.

Animals↗
PubMed1998

Effects of estrous cyclicity on the expression of the galanin receptor Gal-R1 in the rat preoptic area: a comparison with the male.

Variations in the number of galanin receptor (Gal-R1)-expressing cells and levels of Gal-R1 messenger RNA (mRNA) were determined in the preoptic area in intact female rats throughout the phases of the estrous cycle and compared with those in the male. Female and male Wistar rats were fixed by perfusion with 4% paraformaldehyde. Cryostat sections were hybridized with a 35S-labeled antisense Gal-R1 riboprobe. The number of Gal-R1 mRNA-expressing cells was lower in the rostral preoptic area than in the medial preoptic area. During the estrous cycle, the highest number of Gal-R1 mRNA-expressing cells in the rostral preoptic region was detected at 0800 h on proestrus, whereas in the medial preoptic area, the maximum number was observed at 1800 h on estrus. Gal-R1 mRNA levels in individual cells were low during diestrus and increased at estrus in both areas. In the male, the number of mRNA-expressing cells and the hybridization signal were significantly lower than those in females during estrus. The results demonstrate that Gal-R1 gene expression in the preoptic area varies during the estrous cycle and is low in males. Short term treatment of ovariectomized rats with estradiol plus progesterone caused significantly decreased preoptic Gal-R1 mRNA levels compared with those after treatment with estrogen only. These observations suggest that in the preoptic area, expression of Gal-R1 is influenced by progesterone. The variation in Gal-R1 expression is likely to influence the extent to which galanin can influence the preoptic cells implicated in the control of neighboring GnRH cells.

Animals↗
PubMed1999

Alterations in monoamine neurotransmitters and dendritic spine densities at the medial preoptic area after sleep deprivation.

The experiments were conducted on 24 adult male Wistar rats to find out the alterations in the levels of monoamines and dendritic spine densities in the medial preoptic area and cortex after total sleep deprivation. Noradrenaline was reduced in the medial preoptic area, though there was no significant change in the cortex. Dopamine and serotonin were decreased both in the medial preoptic area and in the cortex. Dendritic spine counts in the medial preoptic area and the motor cortex were increased after total sleep deprivation. Enhanced release of the monoamines and their subsequent breakdown during sleep deprivation could be responsible for the decreased levels of the transmitters. An increase in synaptic activity, resulting in the enhanced release of the transmitters, might be responsible for the increased spine density after total sleep deprivation. Localized changes in noradrenaline levels at the medial preoptic area suggest its involvement in sleep genesis and maintenance, though its possible contribution to other functions like thermoregulation and reproduction cannot be ruled out. As the available literature does not indicate a role for serotonin and dopamine at the medial preoptic area in sleep regulation, these changes may represent their participation in non-sleep functions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Integration between the lateral preoptic area and subfornical organ in the regulation of water intake and hemodynamics in the rat.

1. The injection of a hypertonic saline solution (0.2 M NaCl) into the lateral preoptic area of the rat produced an increase in water intake that was further increased by the injection of angiotensin II (4 ng) into the subfornical organ. An increase in arterial pressure was also observed. Increase in heart rate was noted after injection of 0.2 M NaCl into the lateral preoptic area. 2. The injection of hypertonic NaCl into the subfornical organ increased water intake and the injection of 4 ng of angiotensin II into the lateral preoptic area augmented this effect. The injection of 0.2 M NaCl into the subfornical organ did not affect blood pressure or heart rate, whereas the injection of angiotensin II into the lateral preoptic area resulted in an increase in these parameters. 3. Intravenous perfusion of angiotensin II (40 ng microliters-1 min-1) caused increased water intake, arterial pressure and heart rate. Dehydration of the lateral preoptic area by 0.2 M NaCl resulted in a summation of effects for water intake alone. 4. Intravenous perfusion with 0.5 M NaCl caused an increase in water intake which was further increased after the injection of angiotensin II (4 ng) into the subfornical organ and angiotensin II (4 ng) into the lateral preoptic area. Arterial pressure and heart rate also increased, remaining unchanged when angiotensin II was injected into the subfornical organ or into the lateral preoptic area. 5. These results suggest interactions between the two areas in the regulation of cardiovascular and thirst mechanisms. However, cardiovascular regulation and the regulation of body fluids may be stimulated by physiological responses to separate mechanisms.

Angiotensin II↗
PubMed1993

Neuronal projections to the medial preoptic area of the sheep, with special reference to monoaminergic afferents: immunohistochemical and retrograde tract tracing studies.

The preoptic area contains most of the luteinizing hormone releasing hormone immunoreactive neurons and numerous monoaminergic afferents whose cell origins are unknown in sheep. Using tract tracing methods with a specific retrograde fluorescent tracer, fluorogold, we examined the cells of origin of afferents to the medial preoptic area in sheep. Among the retrogradely labeled neurons, immunohistochemistry for tyrosine hydroxylase, dopamine-beta-hydroxylase, phenylethanolamine N-methyltransferase, and serotonin was used to characterize catecholamine and serotonin fluorogold labeled neurons. Most of the afferents came from the ipsilateral side to the injection site. It was observed that the medial preoptic area received major inputs from the diagonal band of Broca, the lateral septum, the thalamic paraventricular nucleus, the lateral hypothalamus, the area dorsolateral to the third ventricle, the perimamillary area, the amygdala, and the ventral part of the hippocampus. Other numerous, scattered, retrogradely labeled neurons were observed in the ventral part of the preoptic area, the vascular organ of the lamina terminalis, the ventromedial part of the hypothalamus, the periventricular area, the area lateral to the interpeduncular nucleus, and the dorsal vagal complex. Noradrenergic afferents came from the complex of the locus coeruleus (A6/A7 groups) and from the ventro-lateral medulla (group A1). However, dopaminergic and adrenergic neuronal groups retrogradely labeled with fluorogold were not observed. Serotoninergic fluorogold labeled neurons belonged to the medial raphe nucleus (B8, B5) and to the serotoninergic group situated lateral to the interpeduncular nucleus (S4). In the light of these anatomical data we hypothesize that these afferents have a role in the regulation of several functions of the preoptic area, particularly those related to reproduction. Accordingly these afferents could be involved in the control of luteinizing hormone releasing hormone (LHRH) pulsatility or of preovulatory LHRH surge.

Animals↗
PubMed1983

The hypothalamus of Lacerta sicula R. II. A Golgi study of the preoptic area.

An analysis of the preoptic area of the lizard, Lacerta sicula R., with the use of the Golgi method revealed that: 1) in principle, the dendritic pattern of its neurons is relatively simple; 2) the supraoptic nucleus contains large- to medium-sized bipolar or multipolar neurons together with small, usually multipolar nerve cells; 3) the preoptic periventricular gray and the paraventricular nucleus exhibit a varied neuronal typology, including large multipolar or bipolar elements, abundant CSF-contacting neurons and some tufted elements; and 4) the lateral regions display some conspicuous multipolar neurons.

Animals↗
PubMed1995

Estrogen receptor mRNA levels in the preoptic area of neonatal rats are responsive to hormone manipulation.

Testosterone, after conversion to estrogen, masculinizes the developing preoptic area (POA) of rats, via binding to intracellular estrogen receptors located within the POA. Our previous studies have shown what seems to be a paradox, in that the levels of estrogen receptor mRNA are lower in males than in females. In the present study, we examined the effects of hormone manipulations on estrogen receptor (ER) mRNA levels in the preoptic area of neonatal male and female rats to test the hypothesis that gonadal steroid hormones regulate ER mRNA during the perinatal period. The relative amount of steady state ER mRNA was assessed in the preoptic area of postnatal day 4 animals using in situ hybridization and film autoradiography. Hybridization density was approximately 2-fold higher in females compared with hybridization density in males. Depletion of testosterone by bilateral removal of the testes on the day of birth increased the level of ER mRNA in males to that observed in females. Treatment of females with the synthetic estrogen, diethylstilbestrol (1 microgram per day, in pellet form), reduced ER mRNA levels to a level comparable to that in intact males. The non-aromatizable androgen, dihydrotestosterone (50 micrograms per day, in pellet form), had no effect on ER mRNA in females. These results suggest that estrogen, derived from the local aromatization of circulating testosterone, down-regulates ER mRNA in the neonatal male preoptic area. Down-regulation of ER mRNA may be an important estrogen-regulated event in the process of sexual differentiation of the preoptic area.

Animals↗
PubMed1990

Ultrastructural analysis of estrogen receptor immunoreactive neurons in the medial preoptic area of the female rat brain.

Neurons of the medial preoptic area were studied in the brain of the female rat by means of ultrastructural immunocytochemistry using a monoclonal antibody generated against purified estrogen receptor (ER), in order to delineate the morphological correlates of estrogen feedback mechanisms. In addition to the preoptic area, the bed nucleus of the stria terminalis, the arcuate and ventromedial nuclei of the hypothalamus exhibited an intense labelling for estrogen receptor. At the light microscopic level, the cell nuclei were immunoreactive. No major alterations were detected in the ER expression of medial preoptic neurons sampled during the estrous cycle, but proestrous rats did exhibit a slightly increased intensity of staining. At the ultrastructural level, the ER immunoreactivity was primarily confined to the nuclei and associated with the chromatin. Long term steroid deprivation elicited by either ovariectomy or ovariectomy plus adrenalectomy resulted in a marked intensity of nuclear labelling. This pattern was not influenced by acute estradiol replacement. These morphological data indicate that neurons of the medial preoptic area have the capacity to detect estrogens via receptor mechanisms and that changes in the level of the circulating ligand are manifested in an alteration in the staining for the estrogen receptor. The study also supports the revised concept of estrogen receptor action by demonstrating the presence of receptors in the nuclei of the cells, whether or not they are occupied by their ligand.

Adrenal Glands↗
PubMed1996

Estradiol regulation of alpha 1b-adrenoceptor mRNA in female rat hypothalamus-preoptic area.

Estradiol treatment for 48 h increases the density of alpha 1B-adrenoceptors in the hypothalamus-preoptic area of ovariectomized female rats by five- to six-fold. Present studies tested the hypothesis that estradiol elevation of hypothalamus-preoptic area alpha 1B-adrenoceptor density is correlated with increased levels of mRNA for this receptor. We developed a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) protocol for measuring brain alpha 1b-adrenoceptor mRNA. The primers chosen yielded the predicted 409 base pair PCR product when used to amplify authentic alpha 1b-adrenoceptor cDNA. The identity of the RT-PCR products from rat brain was confirmed by restriction digest analysis and sequencing. Moreover, there was a good correlation between the levels of alpha 1b-adrenoceptor mRNA measured by RT-PCR in liver, whole brain and cerebellum with previous measurements using Northern blots and RNAse protection assays. We then performed RT-PCR on total RNA from hypothalamic-preoptic area tissue taken from ovariectomized control rats and from ovariectomized rats injected once or twice with 2 micrograms of estradiol benzoate at 24 or 24 and 48 h before sacrifice. Exposure to estradiol for either 24 or 48 h significantly increased levels of alpha 1b-adrenoceptor mRNA by 86-110% in the hypothalamus-preoptic area of ovariectomized female rats when compared to oil-treated controls. We also examined whether estradiol regulates alpha 1b-adrenoceptor mRNA in the cortex. Cortical alpha 1b-adrenoceptor mRNA levels were reduced to approximately 20% of control levels when measured 24 h after hormone injection. A similar decrease in cortical alpha 1b-adrenoceptor mRNA was observed 48 h after estrogen administration. In summary, estradiol treatment significantly increases the level of alpha 1b-adrenoceptor mRNA in the hypothalamus-preoptic area, a brain region involved in the control of reproductive function. In the cortex, a brain region with relatively few estrogen receptors, the same estrogen treatment reduces alpha 1b-adrenoceptor mRNA levels.

Animals↗
PubMed1996

Low doses of neurotensin in the preoptic area produce hyperthermia. Comparison with other brain sites and with neurotensin-induced analgesia.

High amounts of neurotensin (NT) are found in the preoptic area of the hypothalamus, an area known to be involved in the regulation of body temperature. It is generally believed that NT is a peptide that produces hypothermia, and several sites in the brain have been proposed to mediate NT-induced hypothermia, including the preoptic area. However, the doses of NT used in these experiments were always very high (microgram order) whereas, according to Goedert, the total brain content of NT in the rat does not exceed 10 ng. We therefore reinvestigated the effects of microinjections of NT in the brain, using high (5 micrograms) and low (50 and 5 ng) doses, into the preoptic area and other brain sites (cerebral ventricles, posterior hypothalamus, and nucleus accumbens), and we also studied, as a comparison, the effects of high and low doses of NT on pain sensitivity in the same sites. The results show that the preoptic area has unique properties in the regulation of body temperature: low doses of NT in the preoptic area produce a hyperthermic response, whereas high doses produce hypothermia. In comparison, NT produces hypothermia in the posterior hypothalamus whatever the dose, and NT has analgesic effects in the preoptic area only at high doses. Besides, NT has no thermic effect, but does have an analgesic effect, in the nucleus accumbens. The selectivity of the actions of high doses of NT, as well as the mechanism of action of NT (possibly an endogenous neuroleptic), are discussed.

Analgesia↗
PubMed2002

Regulation of glutamic acid decarboxylase 65 and 67 gene expression by ovarian steroids: identification of two functionally distinct populations of GABA neurones in the preoptic area.

GABA neurones in the preoptic area (POA) are critical for oestradiol (E2)-dependent surge release of luteinizing hormone (LH); however, it is not clear which population(s) of POA GABA neurones is involved. The goals of the present studies were: (i) to determine whether E2 regulates GABA neurones similarly in two subdivisions of the POA that play a role in LH surge release, the rostral POA region that contains the organum vasculosum of the lamina terminalis (rPOA/OVLT), and the region containing the anteroventral periventricular nucleus (AVPV) and medial preoptic nucleus (MPN) and (ii) to determine whether GABA neurones in either or both regions exhibit temporal changes consistent with a role in the regulation of LH surge release. To accomplish these goals, we measured glutamic acid decarboxylase (GAD) 65 and 67 mRNA levels at several time points in ovariectomized (OVX), E2-treated OVX rats exhibiting LH surge release, and in E2-treated OVX rats in which LH surge release was blocked by prior administration of progesterone (P4). Our findings demonstrate that, despite their close proximity, GABA neurones in the AVPV/MPN region are regulated differently from those in the rPOA/OVLT. Only neurones in the AVPV/MPN region show temporal changes in GAD 67 mRNA expression that appear to be linked to positive-feedback effects of E2 on luteinizing hormone-releasing hormone (LHRH) and LH release. Our findings also indicate that a morning rise and an afternoon fall in GAD 67 mRNA levels marks two E2-dependent signals required for LHRH and LH surge release. Finally, our results suggest that there are distinct E2-induced signals to the rPOA/OVLT and AVPV/MPN regions and that these signals differentially regulate GAD 65 and 67 gene expression.

Animals↗
PubMed1992

Distribution of substance P-immunoreactive elements in the preoptic area and the hypothalamus of the rat.

The localization and morphology of neurons, processes, and neuronal groups in the rat preoptic area and hypothalamus containing substance P-like immunoreactivity were studied with a highly selective antiserum raised against synthetic substance P. The antiserum was thoroughly characterized by immunoblotting; only substance P was recognized by the antiserum. Absorption of the antiserum with synthetic substance P abolished immunostaining while addition of other hypothalamic neuropeptides had no effect on the immunostaining. The specificity of the observed immunohistochemical staining pattern was further confirmed with a monoclonal substance P antiserum. The distribution of substance P immunoreactive perikarya was investigated in colchicine-treated animals, whereas the distribution of immunoreactive nerve fibers and terminals was described in brains from untreated animals. In colchicine-treated rats, immunoreactive cells were reliably detected throughout the preoptic area and the hypothalamus. In the preoptic region, labeled cells were found in the anteroventral periventricular and the anteroventral preoptic nuclei and the medial and lateral preoptic areas. Within the hypothalamus, immunoreactive cells were found in the suprachiasmatic, paraventricular, supraoptic, ventromedial, dorsomedial, supramammillary, and premammillary nuclei, the retrochiasmatic, medial hypothalamic, and lateral hypothalamic areas, and the tuber cinereum. The immunoreactive cell groups were usually continuous with adjacent cell groups. Because of the highly variable effect of the colchicine treatment, it was not possible to determine the actual number of immunoreactive cells. Mean soma size varied considerably from one cell group to another. Cells in the magnocellular subnuclei of the paraventricular and supraoptic nuclei were among the largest, with a diameter of about 25 microns, while cells in the supramammillary and suprachiasmatic nuclei were among the smallest, with a diameter of about 12 microns. Immunoreactive nerve fibers were found in all areas of the preoptic area and the hypothalamus. The morphology, size, density, and number of terminals varied considerably from region to region. Thus, some areas contained single immunoreactive fibers, while others were innervated with such a density that individual nerve fibers were hardly discernible. During the last decade, knowledge about neural organization of rodent hypothalamic areas and mammalian tachykinin biochemistry has increased substantially. In the light of these new insights, the present study gives comprehensive morphological evidence that substance P may be centrally involved in a wide variety of hypothalamic functions. Among these could be sexual behavior, pituitary hormone release, and water homeostasis.

Animals↗
PubMed1988

Positive feedback in hypogonadal female mice with preoptic area brain transplants.

When fetal preoptic area (POA) brain grafts that contain gonadotropin-releasing hormone cells are transplanted into the third ventricle of adult female hypogonadal mice, the animals respond with sexual maturation, persistent estrus, and the ability to ovulate reflexively after mating. However, the absence of normal spontaneous ovulatory cyclicity suggests an impairment in positive feedback. We, therefore, studied the effect of administration of progesterone alone or of sequential estradiol benzoate and progesterone on plasma levels of luteinizing hormone (LH) in groups of hypogonadal (HPG) mice in persistent estrus after receiving POA grafts (HPG/POA). Individual differences in responsivity to progesterone were related in part to the length of time in persistent estrus. Approximately 30% of HPG/POA grafts tested 2 months after graft showed increased levels of plasma LH. This was reduced to 10% when animals were tested 5 months after graft. Sequential administration of estradiol benzoate plus progesterone to intact HPG/POA mice was ineffective in elevating LH. The presence of corpora lutea in ovaries verified that only animals with a progesterone induced LH surge ovulated. Other HPG/POA mice were mated, and the occurrence of reflex ovulation was determined. Four of these mice delivered pups: 3 were previous responders to progesterone. One female mated again during the immediate postpartum period and delivered a second litter. Following weaning of all offspring, this animal displayed spontaneous ovarian cyclicity, confirmed by ovarian histology. This is the first proven example of spontaneous ovulation in a mutant mouse with a brain graft. The results show that some HPB/POA mice are capable of positive feedback responses, and rarely, of becoming spontaneous ovulators.

Animals↗
PubMed1978

Activation of hypothalamic neuronal activity by the electrolytic deposition of iron into the preoptic area.

Changes in brain activity after electrochemical stimulation of the preoptic area of pro-oestrous rats were studied by the measurement of the electro-encephalogram (EEG) of the frontal cortex and the recording of single neurones in the anterior hypothalamus. All rats were anaesthetized with urethane between 10.00 and 12.00 h to allow prolonged electrophysiological recording and to block the spontaneous surge of LH during the afternoon. Electrochemical stimulation was applied, between 12.00 and 14.00 h, as an anodal current through an implanted steel electrode; this caused the electrolytic deposition of iron and evoked the release of LH and ovulation. Electrochemical stimulation of the preoptic area changed the cortical EEG, either immediately or after a delay of a few minutes, from a labile pattern with alternate periods of arousal and slow-wave sleep, to a stage of continuous arousal which persisted for the remainder of the recording period (2--3 h). Conversely, the EEG pattern of the cortex was not disturbed by electrolytic lesions placed in the preoptic area through a platinum electrode. Electrochemical stimulation of the arcuate region of the hypothalamus, the lateral septal area, the medial amygdaloid complex and the anterior parts of the thalamus caused no obvious change in the EEG patterns. Ipsilateral anterior hypothalamic neurones, about 1 mm caudal to the focus of electrochemical stimulation, displayed an immediate decrease in electrical activity after application of the current. After 10--20 min however, the rates of discharge of action potentials in 9 out of the 16 neurones under consideration increased progressively from 0.5 to 15--25 action potentials/s and these rates were maintained until the recordings were lost after 90--230 min. No such acceleration in electrical activity was observed in neurones on the contralateral side. Iron deposited during electrochemical stimulation was precipitated as sulphide and stained by Timm's method. There was a central damaged area of radius 0.6 mm surrounded by an 'undamaged' area with considerable infiltration of iron, up to a distance of 1.7 mm from the electrode tip. Cells within the area of infiltration did not stain for iron 10 min after electrochemical stimulation, but after 30 min, neural elements in this peripheral zone were stained in a manner similar to the Golgi method. The concentrations of LH in the plasma remained unchanged in all rats for 10--15 min after electrochemical stimulation. Thereafter, the concentrations increased progressively and approximately in parallel to the changes in action potential activity until, after 2 h, the individual concentrations of 300--600 ng LH/ml were more than six times the values obtained before stimulation. Bilateral electrochemical stimulation resulted in appreciably higher concentrations of LH and produced values close to those observed during the pro-oestrous surge of the hormone...

Action Potentials↗
PubMed2000

Changes in sleep-wakefulness after 6-hydroxydopamine lesion of the preoptic area.

This study was undertaken to assess the role of catecholamine fibers, terminating in the preoptic area, in regulating sleep-wakefulness in rats. Sleep-wakefulness was assessed on the basis of 24h electroencephalogram, electromyogram and electro-oculogram recordings before and after destruction of catecholaminergic terminals at the medial preoptic area by bilateral intracerebral injection of 6-hydroxydopamine (8 microg in 0.2 microl). There was a mild reduction in sleep and increase in wakefulness after the lesion. The increase in active wakefulness observed after eight days of lesion persisted even on the 12th day. In spite of the reduction in sleep, the day-night sleep ratio was not affected by 6-hydroxydopamine lesion of the preoptic area. The results indicate that the noradrenergic fibers at the preoptic area have a hypnogenic role.

Activity Cycles↗
PubMed1993

Perinatal and adult factors responsible for the sexually dimorphic calcitonin gene-related peptide-containing cell population in the rat preoptic area.

Neurons containing calcitonin gene-related peptide in the medial preoptic nucleus exhibit the largest neurochemically defined sex difference in the rat preoptic area with a 20-fold difference in cell numbers. The gonadal steroid hormones responsible for this sexual dimorphism have been investigated by examining calcitonin gene-related peptide immunoreactivity in the preoptic area of adult rats receiving a variety of perinatal and adult gonadal steroid manipulations. Cells immunoreactive for calcitonin gene-related peptide were examined in two populations within the preoptic area, one in its ventrolateral aspect and the other located in the lateral division of the medial preoptic nucleus. Cell profile counts estimate numbers of calcitonin gene-related peptide-containing cells in the medial preoptic nucleus of the female to be 22.2 +/- 3.0 cells/section compared with 1.0 +/- 0.2 in the male (P < 0.01). No sex differences existed in the preoptic ventrolateral population of calcitonin gene-related peptide cells (males 4.3 +/- 0.2, females 4.4 +/- 0.6 cells/section). Gonadectomy of male rats on postnatal day 2 resulted in the appearance of a calcitonin gene-related peptide-containing cell population in the medial preoptic nucleus which was indistinguishable from intact female rats (19.3 +/- 2.2 cells/section). Gonadectomy of adult male rats resulted in a modest increase in calcitonin gene-related peptide cell numbers within the medial preoptic nucleus (8.8 +/- 0.4 cells/section) and this was fully reversed by replacement of testosterone (0.7 +/- 0.2 cells/section).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1988

Regional sex differences in cell nuclear estrogen-binding capacity in the rat hypothalamus and preoptic area.

Estrogen binding was compared in cell nuclear KCl extracts from microdissected brain regions of gonadectomized-adrenalectomized male and female rats treated with a near-saturating dose of 17 beta-estradiol. Injection of 3.6 or 36.0 micrograms 17 beta-estradiol/kg BW, iv, 1 h before death resulted in a higher level of estrogen binding in the periventricular preoptic area (PVPOA), medial preoptic area, and ventromedial nucleus of the hypothalamus (VMN) of the female than in comparable tissue samples from the male. No significant sex differences in nuclear estrogen binding were observed in the arcuate-median eminence region, bed nucleus of the stria terminalis, or corticomedial amygdala. Scatchard analysis of saturation binding data revealed that the sex differences in cell nuclear estrogen binding in the PVPOA, medial preoptic area, and VMN reflect a difference in binding capacity rather than binding affinity. These in vitro biochemical findings were confirmed by autoradiographic studies. Gonadectomized-adrenalectomized animals were injected with 125I-labeled 11 beta-methoxy-16 alpha-iodoestradiol (2.0 micrograms/kg BW). Thin frozen sections (10 microns) through the preoptic area and hypothalamus were thaw-mounted onto microscope slides, then exposed against LKB Ultrofilm for 21 days. The autoradiographic images exhibited similar silver distributions and densities in males and females in the arcuate-median eminence region bed nucleus of the stria terminalis, and amygdala. However, 11 beta-[125I]methoxy-16 alpha-iodoestradiol uptake was lower in males than in females in the PVPOA and VMN. These results suggest that sex differences in responsiveness to estrogen stimulation in the rat may be due in part to sex differences in estrogen-binding capacity in specific regions of the hypothalamus that play important roles in the control of pituitary function and reproductive behaviors.

Adrenalectomy↗
PubMed1985

Karyometric changes in the development of the medial and lateral preoptic area of the mouse after gonadectomy.

A karyometric study of the medial and the lateral preoptic area of the male albino mouse has been carried out with the aid of a Leitz Image Analysis System (ASM). We have measured nuclear sizes of a control group of sixty mice, aged from the 5th to the 190th day of life. Another group of prepuberally castrated male mice, has been studied at the 25th, 35th, 45th, 55th and 85th postnatal day. The medial and the lateral preoptic area show different development patterns in the control group, and differential effects of castration in these zones were observed. The medial preoptic area, which has frequently been related to changes of sex hormone levels, experiments more important and statistically significant variations than the lateral preoptic area.

Aging↗