Thyrotropin-releasing hormone hyperactivity in the preoptic area of spontaneously hypertensive rats

Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation through the activation of different neurotransmitter systems at distinct extrahypothalamic sites. To study possible alterations in the TRH system in the hypertensive state, we measured TRH concentration in cerebrospinal fluid and TRH content of the preoptic area in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) by radioimmunoassay. In addition, we also measured the density of the TRH receptor in this area by a rapid filtration technique using [3H]methyl-TRH. We found a significant increase in both the TRH content (634 +/- 61 versus 350 +/- 26 pg/mg protein, SHR versus WKY; P < .01, n = 5) and density of TRH receptors without changes in affinity (Bmax, 5.0 +/- 0.1 versus 3.3 +/- 0.1 fmol/mg protein, P < .01, n = 4). An increase in TRH concentration was also found in the cerebrospinal fluid of SHR (30 +/- 3 versus 21 +/- 2 pg/mL, P < .01, n = 5), suggesting increased TRH release in the central nervous system. Northern blot analysis indicated a threefold augmented abundance of TRH precursor mRNA in the preoptic area of SHR. A polyclonal antibody raised against TRH injected peripherally or intracerebroventricularly lowered arterial blood pressure in SHR but not in WKY. In addition, long-term treatment with enalapril (5 mg/kg twice daily), which was effective in inhibiting serum angiotensin-converting enzyme activity by more than 50%, decreased arterial blood pressure and preoptic area TRH content of SHR, whereas another vasodilator, diltiazem (10 mg/kg every 8 hours), failed to produce a similar change.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II-induced hypertension: effects on central and peripheral atrial natriuretic peptide

Angiotensin (Ang) II and atrial natriuretic peptide (ANP) have opposing effects on blood pressure, sympathetic activity, vasopressin and ACTH secretion, salt appetite, and drinking. We observed their interaction by infusing Ang II (7.2 nmol/h) into the peritoneum (i.p.) or into the lateral ventricle (i.c.v.) of rats with osmotic minipumps for seven days. At sacrifice, rats receiving Ang II-i.c.v. had a systolic blood pressure of 184 +/- 3 (SEM) mmHg, those receiving Ang II-i.p. had 159 +/- 5 mmHg (p < 0.05), while controls had 109 +/- 2 and 110 +/- 2 mmHg, respectively (p < 0.05). Drinking and urine volume increased similarly in rats receiving Ang II by either route, while Uosm decreased. Renin (PRA) values were lower (p < 0.05) in rats receiving Ang II-i.c.v. (0.7 +/- 0.2 ng Ang l/ml/h) or Ang II-i.p. (0.9 +/- 0.2) than in the respective controls (2.3 +/- 0.7 and 2.0 +/- 0.3). Plasma ANP values with Ang II-i.c.v. (18 +/- 1.6 pg/ml) or with Ang II-i.p. (49 +/- 6) were also lower (p < 0.05) than respective controls (89 +/- 12, 76 +/- 4). Vasopressin (AVP) concentrations in the plasma were not influenced by the regimens. In the brain, the ANP contents in areas of the so-called AV3V-region (organum vasculosum laminae terminalis, preoptic periventricular nucleus, medial preoptic nucleus) were similarly and significantly reduced by both Ang II-i.c.v. and Ang II-i.p.. ANP values were also reduced in the median eminence by both types of Ang II-treatment, while ANP concentrations in the supraoptic nucleus were increased. The data show that Ang II infusions producing a chronic rise in blood pressure exert similar effects on drinking behavior, PRA, and ANP concentrations in blood and brain. The AV3V area may be pivotal to both models.

Estradiol and testosterone in specific regions of the human female brain in different endocrine states

Post-mortem concentrations of estradiol and testosterone were measured in 17 brain areas, serum and fat in 6 fertile and 5 postmenopausal women. Steroid concentrations were measured with radioimmunoassay after extraction of brain tissue with ethanol and purification with celite chromatography. There were regional differences in brain concentrations of both steroids. The highest levels of estradiol and testosterone were noted in the hypothalamus, preoptic area and substantia nigra. These findings may assist in the interpretation of functional animal studies where the hypothalamus-preoptic area and the nigrostriatal dopamine system have proved to be target areas for estradiol. When compared to postmenopausal women, estradiol concentrations were significantly higher in the brains of fertile women, which indicates that peripheral serum levels of estradiol are reflected in the brain. This study has yielded information about steroid levels in different endocrine states and could provide a frame of reference for studies of estradiol and testosterone mediated effects on the central nervous system.

Differential cellular localization of oestrogen receptor immunoreactivity and oxytocin mRNA and immunoreactivity in the rat preoptic area

Oestrogen influences both oxytocin mRNA and peptide immunoreactivity in the preoptic area and the rat oxytocin gene contains functional oestrogen response elements. However, using combinations of immunocytochemistry and in situ hybridization for oxytocin and oestrogen receptor, we found that preoptic oxytocin neurons do not possess oestrogen receptors. This finding implies oestrogen actions on oxytocin synthesis in preoptic neurones are unlikely to be mediated directly.

Metabotropic glutamate receptor mGluR5 subcellular distribution and developmental expression in hypothalamus

The metabotropic glutamate receptor mGluR5 is a G-protein coupled receptor that plays a key role in release of Ca2+ from internal stores via inositol triphosphate mobilization. Western and Northern blot analyses revealed a greatly enhanced expression of mGluR5 in rats during early stages of hypothalamic development compared with the adult. This enhanced developmental expression provides an explanation for the dramatic physiological response of developing neurons to metabotropic glutamate receptor activation and supports the argument that metabotropic glutamate receptors may play an important role in hypothalamic development. During development, expression of the mGluR5 gene was reduced, not only in the hypothalamus but also in other regions of the brain. A differential decrease in mGluR5 protein was found in different brain regions with Western blot analysis. The hypothalamus showed a sixfold decrease in mGluR5 with development, whereas the cortex showed only a threefold decrease. Immunocytochemistry with an affinity-purified antibody against a peptide deduced from the cloned mGluR5 gene revealed selective expression in some regions in the adult hypothalamus. In the adult and developing (postnatal day 10) brain, immunoreactive neurons were found in the suprachiasmatic nucleus, preoptic area, lateral hypothalamus, and mammillary region, areas where the related metabotropic glutamate receptor mGluR1 is also found. In contrast, the ventromedial nucleus, an area critically involved in the regulation of food intake and metabolic balances, showed strong mGluR5 immunoreactivity but no mGluR1 immunoreactivity. Little or no mGluR5 staining was found in the neurosecretory neurons of the paraventricular, supraoptic, and arcuate nuclei. Ultrastructurally, mGluR5 was associated with the cytoplasmic face of the plasmalemma on hypothalamic dendrites, dendritic spines, and neuronal perikarya in the adult. The strongest immunoreactivity was found in patches on the membrane, sometimes associated with the postsynaptic side of synapses and sometimes associated with nonsynaptic dendritic or perikaryal membrane. Intense immunostaining was found on some astrocyte processes surrounding synaptic complexes containing asymmetrical synapses. These astrocytes would be in an ideal position to receive excitatory signals from glutamatergic axons. Unlike the punctate appearance of immunolabeling on neuronal membranes, astrocytes showed continuous staining along the plasma membrane.

Microdialysis measurement of intracerebral somatostatin in the goat

A microdialysis sampling technique for the intracerebral measurement of somatostatin (SS) in extracellular fluid was examined in the goat. The microdialysis probe (70-mm shaft, 0.5 mm outer diameter) contained at its tip a 4-mm length of copolymer dialysis membrane (20 kDa cut-off). Artificial cerebrospinal fluid (artificial CSF) was pumped through the probe tip at a rate of 4 microliters/min with a batter-driven syringe pump, and effluent fractions of dialysate (120 microliters) were collected every 30 min. An in vitro recovery test showed that changes in the SS concentration in dialysate were highly correlated (r = 0.95, P < 0.01) with those in the external medium, and the relative recovery averaged 2.0%. As a validation for in vivo microdialysis, trails were conducted with conscious behaving goats wherein the inflow dialysate was changed transiently from artificial CSF with low potassium (2.5 mM) to a solution of 300 mM KCl. Potassium-induced depolarization around the probe tip located in the preoptic area and in the hypothalamus induced an increase in SS concentrations in dialysate at each location. In the most remarkable response, the concentrations of SS were increased 6-fold and 11-fold in the first and second 30-min fractions, respectively, compared with prepotassium concentrations. These results suggest that intracerebral SS levels in extracellular fluid could be estimated from conscious behaving goats by the use of our intracerebral microdialysis system.

Migrating luteinizing hormone-releasing hormone (LHRH) neurons and processes are associated with a substrate that expresses S100

Luteinizing hormone-releasing hormone (LHRH) containing neurons arise in the region of the medial olfactory placode and migrate into the developing olfactory bulbs and basal forebrain along branches of the terminal and vomeronasal nerves. The neurons ultimately come to reside in olfactory and septo-preoptic areas and project extensively to several brain regions, including the preoptic area and median eminence. The present study examined the expression of a glial-associated guidance molecule, S100, as a possible substrate for this migration. Monodelphis domestica (the Brazilian grey, short-tailed opossum) was studied since this species gives birth to very immature, young, allowing access to early periods of mammalian forebrain development. Immunoreactivity for both S100 and LHRH-containing neurons and fibers were observed to be closely associated along the entire LHRH migratory route from the vomeronasal organ to the septo-preoptic areas as early as the day of birth (PO). By P10, S100-immunoreactivity was also seen in areas containing LHRH-immunoreactive fibers such as the preoptic area and median eminence. We suggest that S100, a protein with neurotrophic properties in vitro, acts as a guidance molecule for migrating LHRH-immunoreactive neurons and elongating processes.

Autoradiographic localization of D1-like dopamine receptors in the forebrain of male and female Japanese quail and their relationship with immunoreactive tyrosine hydroxylase

The distribution of D1-like dopamine receptors was studied in the brain of male and female Japanese quail (Coturnix japonica) by means of quantitative autoradiography with 3H-labelled D1 selective antagonist, SCH 23390, serving as a ligand. A specific, saturable, high affinity binding of this ligand was demonstrated. High densities of binding sites were detected in the lobus parolfactorius, olfactory tubercle, and paleostriatum augmentatum. Medium densities were observed in the entire neostriatum and in the external layers of the optic tectum. Similar levels of binding outlined the paleostriatum primitivum, the nucleus pretecalis and the nucleus intercollicularis. Low but significant levels of receptors were also present in the medial preoptic area at the level of the sexually dimorphic medial preoptic nucleus and throughout the infundibulum, as well as in the ectostriatum, medial and lateral septum, and nucleus accumbens. At the level of the medial septum, just dorsal to the anterior commissure, two circular areas of high receptor density corresponding to the nucleus of the septal commissure were also observed. No sex difference in receptor density could be detected in any of the areas. All areas containing high densities of D1 receptors also contained high densities of tyrosine hydroxylase (TH) fibers. However, certain areas characterized by a high density of TH-immunoreactive fibers did not contain appreciable densities of D1-like dopamine receptors. The distribution of this receptor and its relationship to TH-immunoreactivity is consistent with observations made in other vertebrates, suggesting that the dopaminergic system is evolutionarily highly conserved among amniote vertebrates.

Sequence analysis of a cDNA encoding an isotocin precursor and localization of the corresponding mRNA in the brain of the cartilaginous fish Torpedo marmorata

The nucleotide sequence of a cDNA encoding an isotocin hormone precursor has been elucidated by analyzing a lambda ZAPII library constructed using poly(A)+ RNA from the brain of the cartilaginous fish Torpedo marmorata. The sequence predicts a precursor of 126 amino acid residues that consists of a signal peptide, the isotocin moiety, and a neurophysin carrier protein. In contrast to other known fish isotocin precursor sequences, the Torpedo neurophysin moiety is not extended at its carboxy-terminus by a copeptin-like sequence. The T. marmorata isotocin precursor exhibits highest amino acid sequence identity (61%) to the toad mesotocin precursor. As demonstrated by in situ hybridization, the isotocin mRNA is present in neurons of the preoptic area of the Torpedo brain.

Non-NMDA glutamate receptors are present throughout the primate hypothalamus

To determine the distributions of glutamate receptors throughout the macaque hypothalamus, we utilized highly specific antipeptide antibodies to visualize alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunits (GluR1, GluR2 and GluR3 [designated as GluR2/3], and GluR4); kainate receptor subunits (GluR6 and GluR7, [designated as GluR6/7]), and a metabotropic receptor (mGluR1 alpha). The results indicate that these glutamate receptors are distributed differentially throughout the monkey hypothalamus. alpha-Amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors are the dominant non-N-methyl-D-aspartate glutamate receptors within the monkey hypothalamus, and the GluR2 subunit is most abundant. GluR1-immunoreactive neurons and neuropil are observed predominantly in the tuberal and mammillary nuclei. GluR2/3-immunoreactive neurons and neuropil have a broader distribution within preoptic, anterior, tuberal, and caudal regions. Separate (but partially overlapping) distributions of GluR1- and GluR2/3-immunoreactive neurons were found, suggesting that the GluR1, GluR2, and/or GluR3 subunits may be coexpressed in subsets of hypothalamic neurons. In contrast, GluR4 immunoreactivity was expressed minimally within monkey hypothalamus. GluR6/7 immunoreactivity was enriched selectively within the suprachiasmatic nucleus. mGluR1 alpha immunoreactivity was present in the mammillary complex. The localization of non-N-methyl-D-aspartate glutamate receptor subunits to neurons throughout the macaque hypothalamus provides further evidence for the glutamatergic regulation of neuroendocrine, autonomic, and limbic circuits. Differential distributions of glutamate receptor subunits may increase the dynamic range of the effects of presynaptic glutamate, allowing for the regulation of several distinct functions subserved by hypothalamic neurons.

Hypophysiotrophic systems in the brain of the Atlantic salmon. Neuronal innervation of the pituitary and the origin of pituitary dopamine and nonapeptides identified by means of combined carbocyanine tract tracing and immunocytochemistry

The neuroanatomical organization of neurons projecting to the pituitary and the origin of pituitary dopamine and nonapeptides were investigated in the brain of the Atlantic salmon (Salmo salar). Carbocyanine tract tracing in combination with tyrosine hydroxylase, arginine vasotocin and isotocin immunocytochemistry for double labelling revealed a previously unknown organization of hypophysiotrophic cell groups and their extrahypothalamic projections, and provide the first direct identification in a teleost fish of the origin of the dopaminergic and nonapeptidergic innervation of the pituitary. The present data include identification of (1) hypophysiotrophic neurons in the ventral telencephalon and in the periventricular preoptic nucleus, (2) large (magnocellular) vasotocinergic hypophysiotrophic neurons in the most rostral extension of the preoptic area, (3) a distinct neuronal group located in a supraoptic/suprachiasmatic position in the anterior periventricular nucleus, that seems to be the major source of dopaminergic innervation of the pituitary, (4) the nonapeptidergic hypophysiotrophic neurons in the preoptic nucleus, (5) hypophysiotrophic neurons in the ventral and posterior hypothalamus of which some are of liquor-contacting type, (6) projections from hypophysiotrophic and non-hypophysiotrophic neurons in the preoptic nucleus to extrahypothalamic areas such as thalamic and periventricular pretectal nuclei, and (7) subdivisions within the preoptic nucleus that exhibit different combinations of hypophysiotrophic and extrahypothalamic efferent connections. Together with previous studies of retinohypothalamic projections and neurochemical organization of hypothalamic/preoptic areas, the present data suggest that the preoptic nucleus and the anterior periventricular nucleus in teleosts possess functional subdivisions with features that resemble those of the paraventricular, supraoptic and suprachiasmatic nuclei of other vertebrates. In the Atlantic salmon, specific dopaminergic and nonapeptidergic neuronal subdivisions are proposed to play a role for photoperiod control of endocrine activity.

Concentration of chicken gonadotropin-releasing hormones I and II in microdissected areas of turkey hen brain during the reproductive cycle

Chicken gonadotropin-releasing hormones I and II (cGnRH I and II) were measured by radioimmunoassay (RIA) in extracts of microdissected regions of turkey hen brain (preoptic area [POA], region of periventricular nuclei [PHN], septum [SEP], hippocampus [HP], dorsomedial thalamus/habenula [DMT], midbrain central gray [MCG], and caudal lateral hypothalamus [LH]) at five stages of the reproductive cycle: before photostimulation, during egg laying, during incubation, during photorefractoriness, and after return to short daylengths. The highest concentration of cGnRH I occurred in PHN, followed by POA, SEP, DMT, HP, LH, and MCG, in decreasing order, whereas the highest concentration of cGnRH II occurred in SEP, followed by POA, DMT, HP, MCG, PHN, LH. These results agree, with some exceptions, with the distribution of fibers and cells as determined by immunohistochemistry. cGnRH II was from 1.3 to 24 times as abundant as cGnRH I in different brain areas. During incubation, cGnRH I concentrations were significantly elevated in the POA and cGnRH II levels were significantly elevated in HP; few other significant differences were detected. Correlation analysis detected occasional significant positive and negative correlations between cGnRH I and II concentrations in forebrain areas and MCG of laying birds and in PHN and LH of incubating birds. These results demonstrate an approximate correspondence between hormone concentrations measured in tissue extracts by RIA and immunohistochemistry and indicate an abundance of cGnRH II as compared with cGnRH I. cGnRH I and II concentrations did not, however, change in parallel in all brain areas, suggesting that these peptides do not function in an exactly parallel fashion. Thus, an extent to which cGnRH II is involved in gonadotropin release remains unresolved.

c-Fos expression during wakefulness and sleep

We have recently demonstrated that c-fos expression is strongly induced by both spontaneous and forced wakefulness in many brain regions. c-Fos expression was considerably increased in regions involved in the regulation of arousal states, such as the locus coeruleus (noradrenergic neurons) and the medial preoptic area (non-GABAergic neurons). With c-fos antisense injection in the medial preoptic area, we demonstrated that c-fos expression in this region is causally involved in sleep regulation. c-Fos expression in other areas, such as the cerebral cortex and the hippocampus, may be related to the functional consequences of prolonged wakefulness and to the need of sleep. Further work should explore the mechanisms leading to changes in the expression of c-fos, and possibly of its target genes, during the sleep-wake cycle.

Hypothalamic estrogen receptor-immunoreactivity in prepubertal vs adult female guinea pigs

Juvenile guinea pigs (18-20 days old) rarely display lordosis in response to estradiol and progesterone treatments that elicit sexual behavior in adult females. Nor do immature animals release a preovulatory-like surge of luteinizing hormone in response to estradiol. In vitro radioligand binding assays have revealed similar concentrations of estrogen receptors in the hypothalamus and preoptic area of prepubertal and adult guinea pigs. The aim of the present study was to compare estrogen receptor-immunoreactivity in a variety of forebrain regions of immature and adult guinea pigs, to determine whether age differences in estrogen receptor levels in more discrete portions of the hypothalamus and preoptic area exist. Forebrain tissue from juvenile (17 days) and adult females (> 6 weeks), ovariectomized 6 days previously, was processed for estrogen receptor-immunoreactivity, using Abbott Laboratories' H222 anti-human estrogen receptor antibody. Juveniles had estrogen receptor-immunoreactive cells in all of the same regions as adults: medial preoptic area, medial preoptic nucleus, bed nucleus of the stria terminalis, periventricular, paraventricular, dorsomedial and arcuate nuclei, ventrolateral and anterior hypothalamic regions, and amygdala. Among the areas in which estrogen receptor-immunoreactivity was quantified (medial preoptic area, medial preoptic nucleus, anterior periventricular nucleus, arcuate nucleus and ventrolateral hypothalamus), the only region in which an age difference in estrogen receptor-immunostaining was observed was the rostral portion of the ventrolateral hypothalamus. Juvenile females had, on average, 30% fewer estrogen receptor-immunoreactive cells in a sample of this region than adults (440 +/- 25 vs. 626 +/- 25, P = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogen receptor and neurotensin/neuromedin-N gene expression in the preoptic area are unaltered with age in Fischer 344 female rats

The sensitivity of hypothalamic centers to estrogenic regulation may be impaired with age and contribute to the loss of reproductive function in female rats. Here, we have tested the hypothesis that aging is associated with alterations in the level of expression of the estrogen receptor (ER) gene and/or the neurotensin/neuromedin-N (NT/N) gene in the preoptic area (POA) of female rats. We have used in situ hybridization histochemistry and quantitative autoradiography to compare ER gene expression and NT/N gene expression in the POA of ovariectomized and ovariectomized/estradiol-treated female rats at 3, 11, and 20 months of age. We found no evidence for an age-related impairment of either ER or NT/N gene expression in two subdivisions of the POA: the anterior medial preoptic nucleus and the medial preoptic nucleus. Likewise, estrogenic regulation of both ER messenger RNA levels and NT/N messenger RNA levels did not differ across age groups. These results indicate that transcription of the ER gene within the POA is not reduced with age and suggest that the receptor translated within the POA functions normally in old female rats. Our observations do not support a role for impaired expression of the ER gene or impaired estrogenic induction of NT/N gene expression by preoptic neurons in the development of reproductive acyclicity with aging.

Seasonal sexually dimorphic distribution of neuropeptide Y-like immunoreactive neurons in the forebrain of the lizard Podarcis hispanica

Since neuropeptide Y (NPY) is involved in several sex-specific physiological and behavioral processes, a sexual dimorphic distribution is expected in forebrain areas that take part in the control of reproduction physiology and sexual behavior. This question has been studied in the lizard Podarcis hispanica by comparing the distribution of NPY-like immunoreactive cells in several forebrain areas of males and females during the season of active (spring/summer) and inactive (fall/winter) reproductive activity. Both qualitative observations and statistical analysis (analysis of variance) indicate that the number of reactive cells within two forebrain areas, the lateral septum and the periventricular preoptic nucleus, depends on the sex (P = 0.02) and season (P = 0.03) and that, in fact, intersexual differences depend on the season of the reproductive annual cycle (P = 0.046). Other areas, such as the amygdaloid nucleus sphericus, show neither sexual dimorphism (P = 0.67), nor seasonal variation in the number of reactive cells (P = 0.18), nor seasonal variation of the intersexual differences (P = 0.75). When analyzed independently, the lateral septum shows a clear sexual dimorphism in favour of females (P = 0.003) whereas the number of reactive cells in the periventricular preoptic nucleus is significantly higher (P = 0.006) in males than in females. In the case of the preoptic nucleus, this sexual dimorphism is clearly accentuated during the season of reproductive activity (P = 0.007), but this dependence is not so clear for the lateral septum (P = 0.059).(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of estrogen receptor-immunoreactive cells in the brain of the rainbow trout (Oncorhynchus mykiss)

Using antibodies against the hormone binding domain of the trout estrogen receptor (ER), the distribution of ER-immunoreactive (ER-IR) cells was studied in the brain of maturing diploid and triploid female rainbow trout using a streptavidin-biotin-peroxidase method followed by a nickel-intensified diaminobenzidine reaction. This technique resulted in an excellent signal/background ratio allowing unambiguous identification of positive cells. In all animals, ER-IR cells were consistently located in three brain regions, the ventral telencephalon, the anterior ventral preoptic region, and the mediobasal hypothalamus. About 250 ER-IR cells were observed in the ventral and dorsal parts of the ventral telencephalon. In the anterior nucleus preopticus periventricularis, about 2400 ER-IR cells were observed surrounding the preoptic recess. In the posterior hypothalamus, approximately 2700 ER-IR cells were located in the anterior, posterior and inferior divisions of the nucleus lateralis tuberis and in the nucleus saccus vasculosus. In these regions cell nuclei exhibiting different densities of staining were observed and absolutely no labeling of cytoplasmic processes was detected. These results are in partial agreement with those obtained either after injection of tritiated-estradiol in other teleots species or in situ hybridization of ER mRNAs in trout. In particular, no immunoreactivity was observed in the thalamic region nor in the nucleus posterioris periventricularis. These data indicate that target cells for estradiol are essentially located in brain regions involved in the neuroendocrine control of pituitary functions and having direct connections with the hypophysis.

Vasotocinergic innervation of sexually dimorphic medial preoptic nucleus of the male Japanese quail: influence of testosterone

The distribution of vasotocin (VT)-immunoreactive (IR) fibers was described in the preoptic and septal regions of the male quail brain. The density of VT-IR fibers was measured in the sexually dimorphic preoptic nucleus (POM) and lateral septum (SL) of adult male quail (Coturnix japonica) by means of quantitative image analysis. Experimental manipulations of the hormonal environment in the peripubertal period influenced this distribution. In both regions, the VT immunoreactivity was reduced or absent when males were castrated. The immunoreactivity was restored to its original level in castrated males by Silastic implants of testosterone. These changes were anatomically specific as evidenced by the fact that the density of VT fibers did not vary in the hypothalamo-neurohypohysial tract as a function of the endocrine condition of the subjects. No change was also observed in the number of VT-IR cells in the periventricular region close to the POM. Previously published data show that VT or its mammalian homolog, vasopressin are implicated in the control of a wide range of instinctive behaviors. The steroid-dependent VT afferents to the POM, a key area controlling male copulatory behavior in quail could therefore be involved in the control of the sexual behavior in this species. The outputs of the POM which contains steroid-receptors could therefore be modulated by steroids in two different ways: directly through the steroid receptors it contains and indirectly through its steroid-sensitive peptidergic afferents.

Sex difference in the neurotensin-immunoreactive cell populations of the preoptic area in quail (Coturnix japonica)

The distribution of neurotensin-immunoreactive cells and fibers was analyzed by immunocytochemistry in the forebrain of male and female Japanese quail (Coturnix japonica) by using an antibody directed against the C-terminal part of the molecule. Immunoreactive perikarya were located almost exclusively in the medial preoptic area with small populations also being present in the nucleus paraventricularis and in the tuberal region. Immunoreactive fibers were observed not only throughout the preoptic area-hypothalamus, but also in the septal region, nucleus intercollicularis, substantia grisea centralis and the classical catecholaminergic areas of the mesencephalon, such as the area ventralis of Tsai and the nucleus tegmenti pedunculo-pontinus, pars compacta. The preoptic neurotensin-immunoreactive cells were exclusively located within the boundaries of the sexually dimorphic medial preoptic nucleus. They were significantly more numerous in females than in males. In females, the number of neurotensin cells varied during the ovulatory cycle: fewer cells were observed in birds that were about to lay an egg (they had a calcified egg in the oviduct) than in those that had already laid or were not going to lay on that day. These data indicate major variations in the expression of neurotensin in response to neurochemical or neuroendocrine changes associated with ovulation.

Regional distribution and in vitro secretion of salmon and chicken-II gonadotropin-releasing hormones from the brain and pituitary of juvenile and adult goldfish, Carassius auratus

The content of salmon (sGnRH) and chicken-II (cGnRH-II) gonadotropin-releasing hormones was measured in discrete brain regions and pituitaries of juvenile and postspawning adult goldfish, using specific radioimmunoassays. In juveniles, the content of both peptides was low. sGnRH was the predominant form in telencephalon-preoptic area (T-POA) (sGnRH:cGnRH-II ratio = 2.06 +/- 0.66) and diencephalon (DIEN) (sGnRH:cGnRH-II ratio = 2.72 +/- 0.32), whereas cGnRH-II was predominant in cerebellum-brain stem (STEM) (sGnRH:cGnRH-II ratio = 0.47 +/- 0.05). Equal amounts of the two peptides were present in pituitary (PIT) (sGnRH:cGnRH-II ratio = 1.04 +/- 0.18). In adults, the content of both peptides in all regions was significantly increased. The increase in sGnRH exceeded that of cGnRH-II in T-POA and PIT, resulting in an increased sGnRH:cGnRH-II ratio in these tissues (T-POA, 3.55 +/- 0.26; PIT, 7.85 +/- 2.28). In DIEN and STEM, the increase in cGnRH-II content equaled or exceeded that of sGnRH; the sGnRH:cGnRH-II ratio was unchanged in STEM (0.39 +/- 0.06) and decreased in DIEN (1.23 +/- 0.13). The secretion of sGnRH and cGnRH-II was investigated under static in vitro incubation conditions. Both forms of the peptide were secreted from T-POA slices and PIT fragments from juvenile and adult fish. Secretion was significantly increased under potassium depolarizing conditions. Secretion of the two peptides was proportional to their content in tissues from both juvenile and adult goldfish.

Effects of photoperiod on reproduction and the gonadotropin-releasing hormone-immunoreactive neuron system in the postpubertal male Djungarian hamster

The present study tested the hypothesis that photoperiodic control of reproductive function in the postpubertal Djungarian hamster is associated with changes in the number, morphology, or distribution of GnRH-immunoreactive cell bodies in the brain. To initiate or arrest sexual maturation, males were reared in long (LD, 16L:8D) or short (SD, 10L:14D) days from birth. In two other groups that were chronologically past the normal onset of puberty, males were transferred at 30 days of age from LD to SD or from SD to LD to arrest or initiate reproductive function, respectively. At 40, 60, or 90 days of age, 4-6 hamsters in each of the four photoperiod treatment groups were killed by intracardiac perfusion. Testes weights were significantly increased in males exposed to long days (LD and SD-to-LD groups) compared to those treated with short days (SD and LD-to-SD groups). Serum FSH concentrations at 40 days of age were also increased in the two groups of males in long days compared to those in both groups in short days (p < 0.05, ANOVA); LH concentrations were unaffected by photoperiod treatments. Brain sections (60 microns) from the corpus callosum decussation to the suprachiasmatic nucleus in the anterior hypothalamus were processed for GnRH immunocytochemistry. In brain regions that contained the majority of GnRH neurons, i.e., the medial preoptic area and diagonal band of Broca, the numbers of GnRH-immunoreactive cell bodies were the same among the four treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A sexually dimorphic population of CRF neurons in the medial preoptic area

The neuropeptide corticotropin-releasing factor (CRF) is thought to mediate the induction of a constellation of behavioral, endocrine, and autonomic responses which are important for an animal's adaptation to stressful events. We have found that the anteroventral periventricular preoptic nucleus (AVPv) and medial preoptic nucleus (MPN) of colchicine-injected female rats contained numerous intensely stained CRF-immunoreactive neurons. The AVPv/MPN in males contained very few CRF-immunoreactive neurons per section, even in colchicine-injected animals. This sexually dimorphic population of CRF-immunoreactive neurons in the AVPv may play some role in the sex-related differences in hormonal responses to stress and/or in the control of female reproductive events.

Relationship between Neuropeptide Y and Luteinizing-Hormone-Releasing Hormone Immunoreactivities in the Hypothalamus and Preoptic Region

The purpose of this study was to examine the anatomical relationships of perikarya and fibers containing neuropeptide Y (NPY) and luteinizing-hormone-releasing hormone (LHRH) in the hypothalamus and preoptic region of female rats. In view of our previous report of stimulatory effects of estrogen on LHRH and NPY levels in the median eminence, animals were bilaterally ovariectomized and subsequently implanted subcutaneously with capsules containing estradiol benzoate in oil or vehicle. Following intracerebroventricular injection of colchicine, rats were perfused with fixative and their brains sectioned and processed for immunohistochemical visualization of NPY and LHRH in the same section and in consecutive sections. Estrogen treatment had no discernible effect on the distribution or relationship of these peptides. NPY-immunoreactive fibers were intimately associated with LHRH-labeled primary dendrites and perikarya in the medial preoptic region and horizontal limb of the diagonal band of Broca. Fibers containing NPY or LHRH overlapped extensively in the lateral palisade region of the median eminence and also in the subependymal and internal zones. The external zone of the median eminence displayed relatively less overlap of these peptide systems. LHRH-immunoreactive axons coursed among NPY-labeled perikarya in the arcuate nucleus and appeared to contact these cells. These results suggest that NPY-containing axons may influence LHRH-positive neurons at the cell body and also at the site of axon termination in the median eminence. LHRH-containing axons appear to contact NPY-immunoreactive perikarya in the arcuate nucleus and may interact with terminals in the median eminence. This arrangement may provide a mechanism for communication between NPY and LHRH neurons and for the neuroendocrine coordination of hypothalamic NPY and LHRH secretion before ovulation.

Competitive PCR for quantitation of gonadotropin-releasing hormone mRNA level in a single micropunch of the rat preoptic area

A competitive polymerase chain reaction (PCR) for quantitating gonadotropin-releasing hormone (GnRH) mRNA level in a single micropunch of the rat preoptic area (POA) is described. The POA (600 microns in depth) was micropunched from frozen rat brain slices and used for mRNA isolation using Dynabeads-oligo(dT) magnetic separation technique. The target RNA combined with a synthetic, deletion mutant GnRH cRNA as an internal standard, is co-reverse transcribed, and their cDNAs are subsequently co-amplified by Taq DNA polymerase in the same tube in which the same GnRH primers are used. This PCR protocol is sensitive enough to detect GnRH mRNA level in a single POA micropunch derived from an individual rat. There is a linear increase of the amount of GnRH PCR products as a function of input RNA and of the number of PCR cycles. Addition of mutant GnRH cRNA as an internal standard allows us to quantitate GnRH mRNA level in biological samples and to compensate variations of PCR reaction between samples. Following preoptic treatment with 5'-ADMP, which depletes selectively norepinephrine (NE), GnRH mRNA level was significantly reduced. This simple, yet highly sensitive PCR method appears to be a valuable tool for the study of the cellular and molecular regulation of GnRH gene expression in a variety of experimental models.

Carbamazepine effects on preoptic GABA release and pituitary luteinizing hormone secretion in rats

In vivo effects of carbamazepine (CBZ) on the neuroendocrine preopticopituitary feedback system were studied by local application of CBZ through a push-pull cannula into the preoptic area and measurement of local effects on gamma-aminobutyric acid (GABA) and distant effects on a subsequent biologic response: luteinizing hormone (LH). Perfusion with 8 and 12 micrograms CBZ/ml cerebrospinal fluid caused a reduction in preoptic GABA release and concomitant suppression of plasma LH levels. These results suggest a GABA component to the mechanism(s) of action of CBZ: (a) CBZ reduces extracellular available GABA concentration, and (b) owing to the known inhibitory role of preoptic GABA in pituitary LH secretion, an increase of postsynaptic GABAergic transmission by CBZ itself could be inferred.