Periventricular Preoptic Nucleus Research Articles

Ontogenetic changes in the tyrosine hydroxylase immunoreactive preoptic area in the small-spotted catshark Scyliorhinus canicula (L., 1758) females: catecholaminergic involvement in sexual maturation.

The catecholaminergic component of the brain-pituitary-gonadal axis, which mediates the influence of external and internal stimuli on the central nervous system and gonad development in vertebrates, is largely unexplored in Chondrichthyes. We considered Scyliorhinus canicula (L., 1758) females as a model for this vertebrate's class, to assess the involvement of the catecholaminergic system of the brain in its reproduction. Along the S. canicula reproductive cycle, we characterized and evaluated differences in somata morphometry and the number of putative catecholaminergic neurons in two brain nuclei: the periventricular preoptic nucleus, hypothesized to be a positive control for ovarian development, and the suprachiasmatic nucleus, examined as a negative control. 16 S. canicula wild females were sampled and grouped in maturity stages (immature, maturing, mature, and mature egg-laying). The ovary was histologically processed for the qualitative description of maturity stages. Anti-tyrosine hydroxylase immunofluorescence was performed on the diencephalic brain sections. The immunoreactive somata were investigated for morphometry and counted using the optical fractionator method, throughout the confocal microscopy. Qualitative and quantitative research confirmed two separate populations of immunoreactive neurons. The modifications detected in the preoptic nucleus revealed that somata were more numerous, significantly smaller in size, and more excitable during the maturing phase but decreased, becoming slightly bigger and less excitable in the egg-laying stage. This may indicate that the catecholaminergic preoptic nucleus is involved in the control of reproduction, regulating both the onset of puberty and the imminent spawning. In contrast, somata in the suprachiasmatic nucleus grew in size and underwent turnover in morphometry, increasing the total number from the immature-virgin to maturing stage, with similar values in the more advanced maturity stages. These changes were not linked to a reproductive role. These findings provide new valuable information on Chondrichthyes, suggesting the existence of an additional brain system implicated in the integration of internal and environmental cues for reproduction.

Regulation and neurochemical identity of melanin-concentrating hormone neurones in the preoptic area of lactating mice.

Neurones expressing the melanin-concentrating hormone (MCH) can be found in the medial preoptic area (mPOA) and ventral aspects of the periventricular preoptic nucleus of rats by mid-to-late lactation and this expression disappears after weaning. The transitory expression of MCH in the preoptic area suggests a role for these neurones in the control of the end of lactation. However, the neurochemical identity of mPOA MCH neurones and the regulatory factors that control the transient MCH expression remain largely unknown, especially in the mouse. In the present study, we showed that mice also present the transitory expression of MCH in the mPOA at late lactation. mPOA MCH cells did not colocalise significantly with markers of GABAergic (VGAT), glutamatergic (VGLUT2 and VGLUT3) or dopaminergic (tyrosine hydroxylase) neurones. mPOA MCH cells also did not express Kiss1 or oxytocin. By contrast, approximately 70% and 90% of mPOA MCH neurones colocalised with oestrogen receptor α and prolactin-induced phosphorylated signal transducer and activator of transcription 5 (STAT5), respectively. Finally, we demonstrated that the number of MCH neurones in the mPOA is significantly higher in females during the first lactation, compared to mice on the second lactation or pregnant mice during the first lactation or brain-specific STAT5 knockout mice during the first lactation. In summary, our findings indicate that MCH neurones in the mPOA of lactating mice are sensitive to oestrogens and prolactin. Thus, mPOA MCH expression is possibly influenced by hormonal variations. Furthermore, the STAT5 signalling pathway is likely involved in the regulation of MCH expression in the mPOA of lactating mice.

Genetic Deletion of Esr1 in the Mouse Preoptic Area Disrupts the LH Surge and Estrous Cyclicity.

Estrogen receptor α (ESR1) is critical for the generation of the preovulatory LH surge. Experiments in rodents have indicated a role for neurons located in the anteroventral periventricular area and preoptic periventricular nucleus [termed the rostral periventricular area of the third ventricle (RP3V)] in surge generation. In the current study, we aimed to examine whether ESR1 expressed by RP3V neurons was necessary for the LH surge. The estrous cycles of mice with estrogen receptor α (Esr1) exon 3 flanked by LoxP sites (Esr1 flox) and controls were monitored before and after bilateral stereotactic injection of adeno-associated virus encoding Cre recombinase into the RP3V. This resulted in 84% and 72% decreases in ESR1-immunoreactive cell numbers in the anteroventral periventricular area and preoptic periventricular nucleus, respectively, with no changes in the arcuate nucleus. Beginning three weeks after the adeno-associated virus injection, Esr1 flox mice began to show a loss of estrous cyclicity going, primarily, into constant estrus. Wild-type mice and Esr1 flox mice with injections outside the RP3V or unilateral ablations of ESR1 continued to exhibit normal estrous cycles. Mice were then gonadectomized and given an estradiol replacement regimen to generate the LH surge. This resulted in an absence of cFOS expression in GnRH neurons (1 ± 1% vs 28 ± 4% of GnRH neurons; P < 0.01) and markedly reduced LH surge levels (2.5 ± 0.6 vs 9.1 ± 1.0 ng/mL; P < 0.01) in Esr1 flox mice compared with controls. These results demonstrate that neurons expressing ESR1 within the RP3V are critical for the generation of the LH surge and estrous cyclicity in the mouse.

Tyrosine hydroxylase-immunoreactivity and its relations with gonadotropin-releasing hormone and neuropeptide Y in the preoptic area of the guinea pig

The present study examines the distribution of tyrosine hydroxylase (TH) immunoreactivity and its morphological relationships with neuropeptide Y (NPY)- and gonadoliberin (GnRH)-immunoreactive (IR) structures in the preoptic area (POA) of the male guinea pig. Tyrosine hydroxylase was expressed in relatively small population of perikarya and they were mostly observed in the periventricular preoptic nucleus and medial preoptic area. The tyrosine hydroxylase-immunoreactive (TH-IR) fibers were dispersed troughout the whole POA. The highest density of these fibers was observed in the median preoptic nucleus, however, in the periventricular preoptic nucleus and medial preoptic area they were only slightly less numerous. In the lateral preoptic area, the density of TH-IR fibers was moderate. Two morphological types of TH-IR fibers were distinguished: smooth and varicose. Double immunofluorescence staining showed that TH and GnRH overlapped in the guinea pig POA but they never coexisted in the same structures. TH-IR fibers often intersected with GnRH-IR structures and many of them touched the GnRH-IR perikarya or dendrites. NPY wchich was abundantly present in the POA only in fibers showed topographical proximity with TH-IR structures. Althoug TH-IR perikarya and fibers were often touched by NPY-IR fibers, colocalization of TH and NPY in the same structures was very rare. There was only a small population of fibers which contained both NPY and TH. In conclusion, the morphological evidence of contacts between TH- and GnRH-IR nerve structures may be the basis of catecholaminergic control of GnRH release in the preoptic area of the male guinea pig. Moreover, TH-IR neurons were conatcted by NPY-IR fibers and TH and NPY colocalized in some fibers, thus NPY may regulate catecholaminergic neurons in the POA.

Immunohistochemical detection of corticotropin-releasing hormone (CRH) in the brain and pituitary of the hagfish, Eptatretus burgeri

The distribution of corticotropin-releasing hormone (CRH) in the brain and pituitary of the hagfish Eptatretus burgeri, representing the earliest branch of vertebrates, was examined by immunohistochemistry to better understand the neuroendocrine system of hagfish. CRH-immunoreactive (ir) cell bodies were detected in the preoptic nucleus, periventricular preoptic nucleus, infundibular nucleus of the hypothalamus, and in the nucleus “A” of Kusunoki et al. (1982) in the medulla oblongata. In the brain, CRH-ir fibers were detected in almost all areas except for the olfactory bulb and telencephalon. Bundles of CRH-ir fibers were detected in the dorsal wall of the neurohypophysis. However, CRH-ir fibers were distant from adrenocorticotropic hormone (ACTH) cells in the adenohypophysis, as studied by dual-label immunohistochemistry. Cortisol and corticosterone were detected in the plasma by a combination of reverse-phase high performance liquid chromatography and a time-resolved fluoroimmunoassay. These results suggest that in the hagfish, CRH, ACTH, and corticosteroids exist and that CRH released in the neurohypophysis likely reaches the adenohypophysis via diffusion.

Diencephalic and septal structures containing the avian vasotocin receptor (V1aR) involved in the regulation of food intake in chickens, Gallus gallus

Recently, it was found that the avian central vasotocin receptor (V1aR) is associated with the regulation of food intake. To identify V1aR-containing brain structures regulating food intake, a selective V1aR antagonist SR-49059 that induced food intake was administrated intracerebroventricularly in male chickens followed by detection of brain structures using FOS immunoreactivity. Particularly, the hypothalamic core region of the paraventricular nucleus, lateral hypothalamic area, dorsomedial hypothalamic nucleus, a subnucleus of the central extended amygdalar complex [dorsolateral bed nucleus of the stria terminalis], medial septal nucleus and caudal brainstem [nucleus of the solitary tract] showed significantly increased FOS-ir cells. On the other hand, the supraoptic nucleus of the preoptic area and the nucleus of the hippocampal commissure of the septum showed suppressed FOS immunoreactivity in the V1aR antagonist treatment group. Further investigation revealed that neuronal activity of arginine vasotocin (AVT-ir) magnocellular neurons in the supraoptic nucleus, preoptic periventricular nucleus, paraventricular nucleus and ventral periventricular hypothalamic nucleus and most likely corticotropin releasing hormone (CRH-ir) neurons in the nucleus of the hippocampal commissure were reduced following the antagonist treatment. Dual immunofluorescence labeling results showed that perikarya of AVT-ir magnocellular neurons in the preoptic area and hypothalamus were colabeled with V1aR. Within the nucleus of the hippocampal commissure, CRH-ir neurons were shown in close contact with V1aR-ir glial cells. Results of the present study suggest that the V1aR plays a role in the regulation of food intake by modulating neurons that synthesize and release anorectic neuropeptides in the avian brain.

Neural basis of the stress response in a pufferfish, Takifugu obscurus.

When faced with danger, pufferfish react with both a fast-start escape response and inflation behavior. The neural basis of these stress responses in the pufferfish has not been described. The present study reveals that during inflation behavior, the buccal cavity expands and compresses as a pump to control the direction of water flow and draws water in and out. The inflation involves a series of major anatomical modifications of the head. The greatly enlarged first branchiostegal ray and its associated hyohyoideus abductor muscle are the key mechanisms responsible for this behavior. The nerve branch innervating the hyohyoideus abductor muscle is highly developed, and its central origin at the motor nucleus of the VIIth cranial nerve was revealed by tract-tracing using the carbocyanine dye DiI. The central connections from its origin were found to be several motor nuclei in the medulla and the spinal cord, the nuclei of cranial nerve III and IV in the mesencephalon, and the pretectalis superficialis and periventricular preoptic nuclei in the diencephalon. Both the sympathetic cells and the parvocellular part of the periventricular preoptic nucleus might play a neuro-endocrine role in the rapid movement of the buccal cavity during puffing behavior in this species of pufferfish. The central circuit revealed by this study is hypothesized to mediate the C-start escape behavior and puffing behavior.

Distribution of Galanin and Galanin Receptor 2 in the Pre-optic Area of the Female Guinea Pig.

This study describes the distribution of galanin (Gal) and galanin receptor 2 (GalR2) in the pre-optic area (POA) of the female guinea pig. Frozen sections were undergone for a routine immunofluorescence labelling. Gal and GalR2 display immunoreactivity in all parts of the pre-optic area. Gal shows reactivity both in perikarya and fibres, whereas GalR2 was observed only in perikarya. Gal- and GalR2-immunoreactive (-ir) perikarya were the most numerous in the medial pre-optic area (MPA) with the highest reactivity in its dorsal part. In the median pre-optic nucleus (MPN) and periventricular pre-optic nucleus (PPN), only single Gal- and GalR2-ir neurons were observed. The highest density of Gal-ir fibres was revealed in the PPN and the lowest in the lateral pre-optic area (LPA). The results of this study indicate that the distribution pattern of Gal containing neurons overlaps well with the distribution pattern of GalR2-positive neurons, especially in the MPA. This may suggest GalR2-dependent activity in this brain region.

Neuroendocrine and behavioral effects of maternal exposure to oral bisphenol A in female mice

Bisphenol A (BPA) is a widespread estrogenic compound. We investigated the effects of maternal exposure to BPA at reference doses on sexual behavior and neuroendocrine functions of female offspring in C57BL/6J mice. The dams were orally exposed to vehicle alone or vehicle-containing BPA at doses equivalent to the no observed adverse effect level (5 mg/kg body weight per day) and tolerable daily intake (TDI, 0.05 mg/kg body weight per day) level from gestational day 15 until weaning. Developmental exposure to BPA increased the lordosis quotient in naive females exposed to BPA at the TDI dose only. BPA exposure had no effect on olfactory preference, ability to express masculine behaviors or number of calbindin-positive cells, a sexually dimorphic population of the preoptic area. BPA at both doses selectively increased kisspeptin cell number in the preoptic periventricular nucleus of the rostral periventricular area of the third ventricle in adult females. It did not affect the number of GNRH-positive cells or percentage of kisspeptin appositions on GNRH neurons in the preoptic area. These changes were associated with higher levels of estradiol (E2) at the TDI dose while levels of LH, estrus cyclicity, ovarian and uterine weights, and fertility remained unaffected. Delay in the time of vaginal opening was observed during the postnatal period at TDI dose, without any alteration in body growth. This shows that developmental exposure to BPA at reference doses did not masculinize and defeminize the neural circuitry underlying sexual behavior in female mice. The TDI dose specifically exacerbated responses normally induced by ovarian E2, through estrogen receptor α, during the postnatal/prepubertal period.

Distribution and chemical coding pattern of the cocaine- and amphetamine-regulated transcript (CART) immunoreactivity in the preoptic area of the pig

This study provides a detailed description of cocaine-and amphetamine-regulated transcript (CART) distribution and the co-localization pattern of CART and gonadotropin releasing hormone (GnRH), somatostatin (SOM), neuropeptide Y (NPY), cholecystokinin (CCK), and substance P (SP) in the preoptic area (POA) of the domestic pig. The POA displays a low density of immunoreactive cells and rich immunoreactivity for CART in fibers. CART-immunoreactive (CART-IR) cell bodies were single and faintly stained, and located in the medial preoptic area (MPA) and the periventricular region of the POA. A high density of immunoreactive fibers was observed in the periventricular preoptic nucleus (PPN); a high to moderate density of fibers was observed in the MPA; but in the dorso-medial region of the MPA the highest density of fibers in the whole POA was observed. The lateral preoptic area (LPA) exhibited a less dense concentration of CART-immunoreactive fibers than the MPA. The median preoptic nucleus (MPN) showed moderate to low expression of staining fibers. In the present study, dual-labeling immunohistochemistry was used to show that CART-IR cell bodies do not contain any GnRH and SP. CART-positive fibers were identified in close apposition with GnRH neurons. This suggests that CART may influence GnRH secretion. Double staining revealed that CART-IR structures do not co-express any of the substances we studied, but a very small population of CART-IR fibers also contain SOM, CCK or SP.

Forebrain mapping of secretoneurin‐like immunoreactivity and its colocalization with isotocin in the preoptic nucleus and pituitary gland of goldfish

Secretoneurin, a 33-34 amino acid neuropeptide derived from the proteolytic processing of the secretogranin-II precursor protein, is reasonably well conserved in evolution. Goldfish secretoneurin shares >75% similarity overall with other vertebrate secretoneurin sequences. The secretoneurin peptide has numerous functions that include neuroinflammation, neurotransmitter release, and neuroendocrine regulation. A detailed description of the central distribution of secretoneurin immunoreactivity is only known for the rat. Using our polyclonal antibody against the central, conserved core of the secretoneurin peptide we studied the distribution of secretoneurin-like immunoreactivity in the goldfish brain. Secretoneurin immunoreactivity was found in the olfactory bulb, entopeduncular nucleus, preoptic nucleus, lateral part of the lateral tuberal nucleus, posterior periventricular nucleus, nucleus of the posterior recess, the nucleus of the saccus vasculosus, and nucleus isthmi. Secretoneurin-immunoreactive fibers were found in the dorsal part of the dorsal telencephalon, ventral and lateral parts of the ventral telencephalon, periventricular preoptic nucleus, pituitary, and the ventrocaudal aspect of the nucleus of the lateral recess. The most conspicuous secretoneurin immunoreactivity was found in the magnocellular and parvocellular cells of the preoptic nucleus that project to the pituitary. Double-labeling studies indicated coexpression with isotocin, the fish homolog of mammalian oxytocin. Clear colabeling for secretoneurin and isotocin in fibers terminating in the neurointermediate lobe suggests that secretoneurin maybe coreleased with isotocin. Previous work indicates that secretoneurin stimulates the release of luteinizing hormone from the goldfish anterior pituitary. Our findings further support a reproductive role for secretoneurin and related peptides, given the importance of oxytocin family peptides in reproductive behavior in vertebrates.

Kisspeptin neurons co‐express met‐enkephalin and galanin in the rostral periventricular region of the female mouse hypothalamus

It is now well established that the kisspeptin neurons of the hypothalamus play a key role in regulating the activity of gonadotropin-releasing hormone (GnRH) neurons. The population of kisspeptin neurons residing in the rostral periventricular region of the third ventricle (RP3V), encompassing the anteroventral periventricular (AVPV) and periventricular preoptic nuclei (PVpo), are implicated in the generation of the preovulatory GnRH surge mechanism and puberty onset in female rodents. The present study examined whether these kisspeptin neurons may express other neuropeptides in the adult female mouse. Initially, the distribution of galanin, neurotensin, met-enkephalin (mENK), and cholecystokinin (CCK)-immunoreactive cells was determined within the RP3V of colchicine-treated mice. Subsequent experiments, using a new kisspeptin-10 antibody raised in sheep, examined the relationship of these neuropeptides to kisspeptin neurons. No evidence was found for expression of neurotensin or CCK by RP3V kisspeptin neurons, but subpopulations of kisspeptin neurons were observed to express galanin and mENK. Dual-labeled RP3V kisspeptin/galanin cells represented 7% of all kisspeptin and 21% of all galanin neurons whereas dual-labeled kisspeptin/mENK cells represented 28-38% of kisspeptin neurons and 58-68% of the mENK population, depending on location within the AVPV or PVpo. Kisspeptin neurons in the arcuate nucleus were also found to express galanin but not mENK. These observations indicate that, like the kisspeptin population of the arcuate nucleus, kisspeptin neurons in the RP3V also co-express a range of neuropeptides. This pattern of co-expression should greatly increase the dynamic range with which kisspeptin neurons can modulate the activity of their afferent neurons.

Comparative distribution of cocaine- and amphetamine-regulated transcript (CART) in the hypothalamus of the capuchin monkey (Cebus apella) and the common marmoset (Callithrix jacchus)

Cocaine- and amphetamine-regulated transcript (CART) is widely distributed in the brain of many species. In the hypothalamus, CART neurotransmission has been implicated in diverse functions including energy balance, stress response, and temperature and endocrine regulation. Although some studies have been performed in primates, very little is known about the distribution of CART neurons in New World monkeys. New World monkeys are good models for systems neuroscience, as some species have evolved several behavioral and anatomical characteristics shared with humans, including diurnal and social habits, intense maternal care, complex manipulative abilities and well-developed frontal cortices. In the present study, we assessed the distribution of CART mRNA and peptide in the hypothalamus of the capuchin monkey (Cebus apella) and the common marmoset (Callithrix jacchus). We found that the distribution of hypothalamic CART neurons in these monkeys is similar to what has been described for rodents and humans, but some relevant differences were noticed. Only in capuchin monkeys CART neurons were observed in the suprachiasmatic and the intercalatus nuclei, whereas only in marmoset CART neurons were observed in the dorsal anterior nucleus. We also found that the only in marmoset displayed CART neurons in the periventricular preoptic nucleus and in an area seemingly comprising the premammillary nucleus. These hypothalamic sites are both well defined in rodents but poorly defined in humans. Our findings indicate that CART expression in hypothalamic neurons is conserved across species but the identified differences suggest that CART is also involved in the control of species-specific related functions.

Evidence for Suprachiasmatic Vasopressin Neurones Innervating Kisspeptin Neurones in the Rostral Periventricular Area of the Mouse Brain: Regulation by Oestrogen

In rodents, a circadian signal from the suprachiasmatic nucleus (SCN) is essential for the pro-oestrous surge of gonadotrophin-releasing hormone (GnRH), which, in turn, induces luteinising hormone (LH) surge and ovulation. We hypothesised that kisspeptin (KP) neurones in the anteroventral periventricular and periventricular preoptic nuclei (AVPV/PeN) form part of the communication pathway between the SCN and GnRH neurones. In anterograde track tracing studies, we first identified vasopressin (VP)-containing axons of SCN origin in apposition to KP-immunoreactive (IR) neurones. Studies to quantify this input relied on the observation that VP-synthesising neurones in the SCN differ from other VP systems in their lack of galanin expression. In ovariectomised mice, 30.79 +/- 1.63% of KP-IR perikarya and proximal dendrites within the AVPV/PeN received galanin-negative VP-IR varicosities. Oestrogen-treatment significantly increased the number of KP-IR neurones, with their percentage apposed by galanin-negative VP-IR varicosities (46.95 +/- 1.88%) and the number of VP-IR appositions on individual KP-IR neurones. At the ultrastructural level, the VP-IR terminals formed symmetric synapses with KP-IR neurones, which was in accordance with the morphology of inhibitory synapses established by SCN neurones. By contrast to VP, vasoactive intestinal polypeptide (VIP), which is synthesised by a distinct subset of SCN neurones, occurred only rarely in axons apposed to KP-IR neurones. Altogether, our results are consistent with the hypothesis that KP neurones located in the mouse AVPV/PeN receive circadian information from the SCN via a vasopressinergic monosynaptic pathway, which is enhanced by oestrogen.

Immunohistochemical localization of orexins (hypocretins) in the brain of reptiles and its relation to monoaminergic systems

With the aim of gaining more insight into the evolution of the orexinergic systems in the brain of vertebrates we have conducted a comparative analysis of the distribution of orexin-immunoreactive cell bodies and fibers in two reptiles, the lizard Gekko gecko and the turtle Pseudemys scripta elegans. In both species most immunoreactive neurons were found in the periventricular hypothalamic nucleus and in the infundibular hypothalamus. Only in the gecko, orexinergic cell bodies were present in the dorsolateral hypothalamic nucleus and the periventricular preoptic nucleus. Fiber labeling was observed in all main brain subdivisions but was more abundant in regions such as the septum, preoptic area, suprachiasmatic nucleus, lateral hypothalamic area and median eminence. Less conspicuous was the innervation of the olfactory bulbs, pallial regions, habenula, dorsomedial and dorsolateral thalamic nuclei, torus semicircularis and spinal cord. Double immunohistofluorescence techniques were applied for the simultaneous detection of the orexinergic systems and the catecholaminergic or serotoninergic systems in the brain of reptiles. Actual colocalization of orexins and catecholamines or serotonin in the same neurons was not observed. However, orexinergic innervation was found in dopaminergic, noradrenergic and serotoninergic cell groups, such as the substantia nigra and ventral tegmental area in the midbrain tegmentum, the locus coeruleus, the nucleus of the solitary tract and the raphe nuclei. The comparison of the distribution of orexin-immunoreactive neurons and fibers found in reptiles with those reported for other vertebrates reveals a strong resemblance but also notable variations. In addition, the relation between the orexinergic and monoaminergic systems observed in the brain of reptiles seems to be a shared feature among vertebrates.

Dopaminergic projections to the medial preoptic area of postpartum rats

Dopamine receptor activity in the rodent medial preoptic area (mPOA) is crucial for the display of maternal behaviors, as well as numerous other physiological and behavioral functions. However, the origin of dopaminergic input to the mPOA has not been identified through neuroanatomical tracing. To accomplish this, the retrograde tracer Fluorogold was iontophoretically applied to the mPOA of postpartum laboratory rats, and dual-label immunocytochemistry for Fluorogold and tyrosine hydroxylase later performed to identify dopaminergic cells of the forebrain and midbrain projecting to the mPOA. Results indicate that the number of dopaminergic cells projecting to the mPOA is moderate (∼90 cells to one hemisphere), and that these cells have an unexpectedly wide distribution. Even so, more than half of the dual-labeled cells were found in either what has been considered extensions of the A10 dopamine group (particularly the ventrocaudal posterior hypothalamus and adjacent medial supramammillary nucleus), or in the A10 group of the ventral tegmental area. The rostral hypothalamus and surrounding region also contained numerous dual-labeled cells, with the greatest number found within the mPOA itself (including in the anteroventral preoptic area and preoptic periventricular nucleus). Notably, dual-labeled cells were rare in the zona incerta (A13), a site previously suggested to provide dopaminergic input to the mPOA. This study is the first to use anatomical tracing to detail the dopaminergic projections to the mPOA in the laboratory rat, and indicates that much of this projection originates more caudally than previously suggested.

Prolactin Expression in the Sheep Brain

Accumulating evidence in rodents suggests that a prolactin locally synthesized and released within the brain can act together with that taken up from the circulation to modulate neuroendocrine responses. The present study was designed to identify the regional patterns of prolactin expression in the adult and developing sheep brain. Specifically, we tested the hypothesis that prolactin is expressed in regions of the adult and fetal sheep brain that are critical in the development of neuroendocrine homeostatic and behavioral functions. The expression of prolactin protein in sheep brain was demonstrated by Western blot analysis and brain prolactin mRNA was detected and sequenced using RT-PCR. In situ hybridization histochemistry revealed that prolactin mRNA was expressed in the medial preoptic area, periventricular preoptic nucleus, bed nucleus of the stria terminalis, and in the paraventricular nucleus of the hypothalamus, particularly the ventral region. The neuroanatomical distribution of prolactin mRNA was best visualized in the fetus and prolactin-immunoreactive neurons could also be identified in late gestation fetuses. Brain prolactin mRNA was expressed as early as day 60 of gestation and increased as the fetus aged and peaked at day 135 (term = 147 days). Prolactin mRNA expression did not exhibit a sex difference in the preoptic area, but in the amygdala prolactin mRNA was significantly higher in females than in males at day 100 of gestation. We conclude that prolactin expressed in adult and fetal sheep brain could be involved in neurodevelopment and/or modulation of the neuroendocrine stress axis, although it is too early to rule out other possibilities given the diverse actions that have been attributed to prolactin.

Postnatal Development of Kisspeptin Neurons in Mouse Hypothalamus; Sexual Dimorphism and Projections to Gonadotropin-Releasing Hormone Neurons

The neuropeptide kisspeptin has recently been implicated as having a critical role in the activation of the GnRH neurons to bring about puberty. We examined here the postnatal development of kisspeptin neuronal populations and their projections to GnRH neurons in the mouse. Three populations of kisspeptin neurons located in the 1) anteroventral periventricular nucleus (AVPV) and the preoptic periventricular nucleus (PeN), 2) dorsomedial hypothalamus, and 3) arcuate nucleus were identified using an antisera raised against mouse kisspeptin-10. A marked 10-fold (P<0.01), female-dominant sex difference in the numbers of kisspeptin neurons existed in the AVPV/PeN but not elsewhere. Kisspeptin neurons in the AVPV/PeN of both sexes displayed a similar pattern of postnatal development with no cells detected at postnatal day (P) 10, followed by increases from P25 to reach adult levels by puberty onset (P<0.01; P31 females and P45 males). This pattern was not found in the dorsomedial hypothalamus or arcuate nucleus. Dual immunofluorescence experiments demonstrated close appositions between kisspeptin fibers and GnRH neuron cell bodies that were first apparent at P25 and increased across postnatal development in both sexes. These studies demonstrate kisspeptin peptide expression in the mouse hypothalamus and reveal the postnatal development of a sexually dimorphic continuum of kisspeptin neurons within the AVPV and PeN. This periventricular population of kisspeptin neurons reaches adult-like proportions at the time of puberty onset and is the likely source of the kisspeptin inputs to GnRH neurons.

Analysis of GABAergic neurons in the medial preoptic nucleus and anteroventral periventricular nucleus of the guinea pig hypothalamus by single-cell RT-PCR

Analysis of GABAergic neurons in the medial preoptic nucleus and anteroventral periventricular nucleus of the guinea pig hypothalamus by single-cell RT-PCR

Ontogeny of the somatostatin variant [Pro2,Met13]somatostatin-14 in the brain, pituitary, and sensory organs of the frogRana esculenta

Two forms of somatostatin are expressed in the frog brain, i.e., somatostatin-14 (SS1) and the [Pro(2), Met(13)]somatostatin-14 variant (SS2). We have previously described the ontogeny of SS1-immunoreactive cells in the brain of Rana esculenta. In the present study, we have investigated the distribution of prepro-SS2 (PSS2)-expressing neurons in the brain of the same species during development by using antibodies directed against the N-flanking region of SS2 (PSS2(54-66)). Immunoreactive perikarya first appeared in the ventral hypothalamus at stages IV-VII. Subsequently, positive neurons were seen in the nucleus of the diagonal band of Broca, the anterior preoptic area, the posterior tuberculum (stages VIII-XII), as well as the dorsal (stages XIII-XV) and medial (stages XIX-XX) periventricular preoptic nucleus. At metamorphic climax and in newly metamorphosed frogs, positive perikarya were found in the striatum and in the interpeduncular nucleus. PSS2(54-66)-immunoreactive fibers were already widely distributed during the first stages of development, indicating that SS2 may act as a neuromodulator and/or neurotransmitter during ontogeny. The presence of PSS2(54-66)-positive nerve fibers in olfactory structures suggests that, in tadpoles, SS2 may be involved in the processing of olfactory information. The occurrence of PSS2(54-66)-like immunoreactivity in taste buds, and in the olfactory and vomeronasal organs indicates that SS2 may mediate the unconditioned and reinforcing properties of natural chemicals. Finally, the intenseexpression of PSS2(54-66)-like immunoreactivity in melanotrope cells of the pituitary suggests that SS2 may diffuse toward the pars distalis to regulate the activity of adenohypophysial cells during tadpole development.