Cells In Preoptic Area Research Articles

Cytoglobin Attenuates Neuroinflammation in Lipopolysaccharide-Activated Primary Preoptic Area Cells via NF-κB Pathway Inhibition.

Cytoglobin (Cygb) is a hexacoordinate protein, associated with the transport of oxygen, nitric oxide scavenging, tumor suppression and protection against oxidative stress and inflammation. This protein is expressed in brain areas including the preoptic area (POA) of the anterior hypothalamus, the region responsible for the regulation of body temperature. In this study, we show that Cygb is upregulated in the rat hypothalamus 2.5 h and 5 h after intravenous administration of lipopolysaccharide (LPS). We investigated the effect of treatment with Cygb in POA primary cultures stimulated with LPS for 4 h. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) were measured and the results showed that Cygb reduced the concentrations of both cytokines. We further observed a decrease in immunoreactivity of the inflammatory transcription factor nuclear factor-κB (NF-κB), but not NF-IL6 and STAT3, in the nucleus of Cygb-treated POA cells. These findings suggest that Cygb attenuates the secretion of IL-6 and TNF-α in LPS-stimulated POA primary cultures via inhibition of the NF-κB signaling pathway, indicating that this protein might play an important role in the control of neuroinflammation and fever.

Sexually dimorphic oxytocin receptor-expressing neurons in the preoptic area of the mouse brain

Oxytocin is involved in the regulation of social behaviors including parental behaviors in a variety of species. Oxytocin triggers social behaviors by binding to oxytocin receptors (OXTRs) in various parts of the brain. OXTRs are present in the preoptic area (POA) where hormone-sensitive sexually dimorphic nuclei exist. The present study was conducted to examine whether sex differences exist in the distribution of neurons expressing OXTRs in the POA. Using OXTR-Venus (an enhanced variant of yellow fluorescent protein) mice, the distribution of OXTR-Venus cells in the POA was compared between sexes. The total number of OXTR-Venus cells in the medial POA (MPOA) was significantly greater in females than in males. No detectable OXTR-Venus cells were observed in the anteroventral periventricular nucleus (AVPV) within the MPOA in most of the brain sections from males. We further examined the total number of OXTR-Venus cells in the AVPV and the rest of the MPOA between the sexes. The total number of OXTR-Venus cells in the AVPV in females (615 ± 43) was significantly greater than that in males (14 ± 2), whereas the total number of OXTR-Venus cells in the rest of the MPOA did not differ significantly between the sexes. Thus, the sexually dimorphic expression of OXTR-Venus specifically occurred in the AVPV, but not in the rest of the MPOA. We also examined whether the expression of OXTR in the AVPV is driven by the female gonadal hormone, estrogen. Immunocytochemistry and single-cell RT-PCR revealed the presence of the estrogen receptor α in OXTR-Venus cells in the female AVPV. Moreover, ovariectomy resulted in the absence of OXTR-Venus expression in the AVPV, whereas estrogen replacement therapy restored OXTR-Venus expression. These results demonstrate that the expression of OXTR in the AVPV is primarily female specific and estrogen dependent. The presence of the sexually dimorphic expression of OXTR in the AVPV suggests the involvement of OXTR neurons in the AVPV in the regulation of female-specific behavior and/or physiology.

LHX1-a multifunctional regulator in preoptic area-derived interneuron development.

LHX1-a multifunctional regulator in preoptic area-derived interneuron development.

The DNA Methyltransferase 1 (DNMT1) Controls the Shape and Dynamics of Migrating POA-Derived Interneurons Fated for the Murine Cerebral Cortex.

The proliferative niches in the subpallium generate a rich cellular variety fated for diverse telencephalic regions. The embryonic preoptic area (POA) represents one of these domains giving rise to the pool of cortical GABAergic interneurons and glial cells, in addition to striatal and residual POA cells. The migration from sites of origin within the subpallium to the distant targets like the cerebral cortex, accomplished by the adoption and maintenance of a particular migratory morphology, is a critical step during interneuron development. To identify factors orchestrating this process, we performed single-cell transcriptome analysis and detected Dnmt1 expression in murine migratory GABAergic POA-derived cells. Deletion of Dnmt1 in postmitotic immature cells of the POA caused defective migration and severely diminished adult cortical interneuron numbers. We found that DNA methyltransferase 1 (DNMT1) preserves the migratory shape in part through negative regulation of Pak6, which stimulates neuritogenesis at postmigratory stages. Our data underline the importance of DNMT1 for the migration of POA-derived cells including cortical interneurons.

Characteristic of hypothalamic kisspeptin expression in the pubertal development of precocious female rats

To investigate the potential role of kisspeptin in the advance onset of puberty in precocious puberty, model rats induced by danazol were used to study the developmental expression of hypothalamic kisspeptin. Kisspeptin immunoreactive cells were observed in the arcuate nucleus (ARC), periventricular nucleus (PeN) and preoptic area (POA) in model rats on the day of onset-puberty. On the day of post-puberty, however, the number of kisspeptin immunoreactive cells in ARC and PeN decreased while the number of those cells in POA increased. Kisspeptin immunoreactive cells were not detected in hypothalamus in both normal and model rats at their pre-puberty stages. Furthermore, the expression of hypothalamic Kiss-1 mRNA reached top on the day of onset-puberty in both of the normal and model rats, and the expression of Kiss-1 mRNA increased significantly in the model rats compared with those in the normal ones. Our results indicated that kisspeptin might involve in the advance onset of puberty in danazol induced female precocious model rats.

NSCL-1 and NSCL-2 synergistically determine the fate of GnRH-1 neurons and control necdin gene expression.

To study the role of the bHLH genes NSCL-1 and NSCL-2 in the development of GnRH-1 neurons, we have generated compound mutant mice. Mutant animals die at birth and show a virtually complete absence of GnRH-1 neurons in the posterior parts of the brain at E18.5 and an aberrant morphology of the remaining GnRH-1 neurons in the anterior parts of the brain indicating that NSCL-1 and NSCL-2 might concomitantly control differentiation/migration of GnRH-1 neurons in a cell autonomous manner. To gain further insights into this process, we screened for NSCL target genes using DNA array hybridization and detected necdin, which is deleted in the human Prader-Willi syndrome phenotypically resembling the NSCL-2 mutation. Using chromatin immunoprecipitation and site-directed mutagenesis of the necdin promoter, we demonstrate that NSCLs together with additional cofactors directly control transcription of the necdin gene. NSCL-dependent control of necdin expression might be instrumental for proper neuronal cell differentiation and enable GnRH-1 neurons to migrate.

GABA and glutamate in mating-activated cells in the preoptic area and medial amygdala of male gerbils.

The posterodorsal medial amygdala (MeApd), the posterodorsal preoptic nucleus (PdPN), and the medial cell group of the sexually dimorphic preoptic area (mSDA) contain cells that are activated specifically at ejaculation as assessed by Fos expression. The mSDA also expresses Fos early in the mating context. Because little is known about the neurotransmitters of these activated cells, the possibility that they use gamma-aminobutyric acid (GABA) or glutamate was assessed. Putative glutamatergic cells were visualized with immunocytochemistry (ICC) for glutamate and its neuron-specific transporter. Their distributions were compared with those of GABAergic cells visualized with ICC for the 67-kDa form of glutamic acid decarboxylase (GAD(67)) and in situ hybridization for GAD(67) messenger RNA (mRNA). Colocalization of Fos and GAD(67) mRNA in recently mated males indicated that half of the activated cells in the PdPN, mSDA, and lateral MeApd are GABAergic. Colocalization of Fos and glutamate suggested that a quarter of the activated mSDA and lateral MeApd cells are glutamatergic. The PdPN does not appear to have glutamatergic cells. In the lateral MeApd, the percentage of activated cells that are GABAergic (45%) matches the percentage that project to the principal part of the bed nucleus of the stria terminalis (BST; 43%), and the percentage likely to be glutamatergic (27%) matches the percentage projecting to the mSDA (27%). The latter could help to trigger ejaculation. The distribution of GABAergic and putative glutamatergic cells in the caudal preoptic area, caudal BST, and medial amygdala of male gerbils is also described.

Preoptic AVT Immunoreactive Neurons of a Teleost Fish with Alternative Reproductive Tactics

Recent reports have implicated an important role for arginine vasotocin (AVT) in the socially mediated sexual differentiation of fishes. This study focuses on the plainfin midshipman (Porichthys notatus) which exhibits two male morphs, type I and type II, differing in a suite of behavioral, neurobiological, and endocrine traits. Immunocytochemical techniques were used to detect neurons containing AVT-like peptide in the forebrain of juveniles, adult females, and type I and type II males. AVT immunoreactive (ir) somata were localized to three regions: the terminal nerve ganglion, the preoptic area (POA), and the pineal stalk. The profile area, or size, of AVT-ir POA neurons differed across the four classes of midshipman and was strongly correlated to differences in body size among the groups. By contrast, the number of AVT-ir cells in the POA exhibited no difference across the classes of midshipman. The number of POA cells containing AVT is therefore likely to be set early in development and not to change with the growth of the animal. An analysis of AVT-ir cell number normalized by body mass revealed that the larger morphs, type I males and females, have fewer cells per gram body mass than type II males and juveniles. Therefore, type II males have a juvenile-like AVT POA phenotype with smaller cells and more numerous cells per unit body mass than type I males. Type II males also exhibit more variability in the number of AVT-ir cells found in the POA compared to type I males.

Role of Sex Steroids on the Survival, Neuritic Outgrowth of Neurons, and Dopamine Neurons in Cultured Preoptic Area and Hypothalamus

Morphological sex differences in some discrete brain regions are thought to be developed by the influence of circulating androgen during the perinatal period. In order to know whether the effect of androgen is a direct one, cells derived from neonatal rat preoptic area (POA) and/or hypothalamus were cultured in a serum-free medium, and the effects on survival, process growth of neurons, and dopaminergic function were examined. When the POA cells were exposed to testosterone (T), neuronal survival was greater than the controls, and the frequency distribution of total process length and the number of process branchings were significantly deviated from the controls. Estradiol-17β (E2) and 5α-dihydrotestosterone had less significant effects on these parameters than T. Moreover, the addition of T increased the dopamine (DA) contents of cells and medium DA in the hypothalamic culture. E2 also greatly increased DA content of the medium. These steroids failed to alter the DA levels in the POA cell cultures. These results generally conform to the notion of previous investigators that T has direct effects on the expansion of dendritic elements of the POA and the development of sex difference in the hypothalamic DA neurons, although the effect of T after conversion to E2 cannot be excluded.

Immunohistochemical double-labeling study of gonadotropin-releasing hormone (GnRH)-immunoreactive cells and oxytocin-immunoreactive cells in the preoptic area of the dwarf gourami, Colisa lalia

The distribution of gonadotropin-releasing hormone (GnRH)-immunoreactive (ir) cells in the preoptic area (POA) of the dwarf gourami, Colisa lalia, was immunohistochemically studied. These neurons form cell columns on both sides of the common ventricle, and their axons project to the pituitary gland by forming distinct bundles. Also examined was the distribution of isotocin (IST) cells in the POA by using an anti-oxytocin (OXT) serum which has been proven to crossreact with IST. These two kinds of immunoreactive cells were distributed quite similarly in the POA. However, by using an immunofluorescence double-labeling method on thinner sections we found that a population of small IST cells in the ventral POA were also immunoreactive to GnRH, but that large IST cells in the dorsal POA were not immunoreactive to GnRH, and small GnRH-ir cells in the most ventral POA were not immunoreactive to the OXT antiserum. In the pituitary gland, GnRH-ir fibers were found in both the neurohypophysis and proximal pars distalis, but IST fibers were found only in the neurohypophysis.

GnRH cell size and number in a teleost fish with two male reproductive morphs: sexual maturation, final sexual status and body size allometry.

Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50-100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Culture of rat brain preoptic area neurons: Effects of sex steroids

The aim of the present study was to investigate the direct effects of testosterone (T), estradiol-17α (E2) and 5α-dihydrotestosterone (5α-DHT) on the survival of neurons and the morphology of neuronal processes (the total process length, the number of processes and the number of process branchings) of the cells derived from neonatal rat preoptic area (POA) to analyze the bases of morphological sexual dimorphism of the POA. The POA cells were exposed to sex steroids during 2–14 days of culture in serum-free medium. Neuronal survival was significantly greater in cultures treated with 1.0 nM T than controls. Although T at any concentration tested (0.1,1.0 or 10.0 nM) failed to affect the mean value of the process length, a significant difference was observed in the frequency distribution of total process length between 1.0 nM T-treated cultures and control cultures. By 1.0 nM T, the number of process branchings was also significantly increased. In contrast, the number of neurons and the total process length of neurons were not affected by 5α-DHT. However, the number of process branchings was significantly increased by 0.1 nM 5α-DHT. E2 had no significant effect on any of these parameters. These results suggest that T directly enhances the survival of neurons and increases the dendritic and/or axonic field of the POA, which serves, at least partly, for the development of morphological sexual dimorphism in the rat.

Neuroanatomical specificity in the autoregulation of aromatase-immunoreactive neurons by androgens and estrogens: an immunocytochemical study

Testosterone (T) increases brain aromatase activity (AA) in quail and other avian and mammalian species. It was shown both in quail and in rat that this enzymatic induction results from a synergistic action of androgens and estrogens. These studies provide little information on possible anatomical or cellular specificity of the effect. Using a polyclonal antiserum against human placental aromatase, we have previously identified aromatase-immunoreactive (ARO-ir) neurons in the quail brain and demonstrated that T increases the number of ARO-ir cells in the quail preoptic area (POA) supporting previous evidence that T increases AA in the brain. However, which T metabolites are involved, the actual mechanism of regulation and the possibility of anatomical specificity for these effects are not yet clear. In the present study, we disassociated the effects of androgens and estrogens in aromatase induction by comparin ARO-in neurons of quail treated with T alone or T in the presence of a potent aromatase inhibitor (R76713), which has been shown to depress AA levels and to suppress T-activated copulatory behavior. T increased the number of ARO-ir cells in POA, bed nucleus striae terminalis (BNST) and tuberal hypothalamus (Tu). The T effect was inhibited by concurrent treatment with aromatase inhibitor in Tu, but not in POA and BNST. The differential effect of the aromatase inhibitor fits in very well with our previous studies of the co-localization of aromatase and estrogen receptors. The T effect was blocked by R76713 in areas where ARO-ir and estrogen receptor-ir are generally co-localized (Tu) and was not affected in areas with mainly ARO-ir positive, estrogen receptor-ir negative cells (POA, BNST). This suggests anatomical differences in the expression or clearance of aromatase which may be differentially sensitive to androgens and dependent upon the presence of sex steroid receptors.

Transmitter and peptide actions on hypothalamic neurons in vitro: Implications for lordosis

This article summarizes a series of studies using brain tissue slices of rats to record single-unit activity from the hypothalamic ventromedial nucleus (VMN) and preoptic area (POA), both of which are crucial for the regulation of the estrogen-dependent feminine mating behavior, lordosis. In these studies the actions of acetylcholine (ACh), serotonin (5HT), norepinephrine (NE), luteinizing hormone-releasing hormone (LHRH), arginine-vasopressin (AVP), and oxytocin (OXY) on neuronal activity were investigated. The results show that these agents could evoke either direct responses or neuromodulatory changes from VMN or POA cells in vitro. Comparison of the net neuronal actions of each of these agents with their effects on lordosis behavior revealed interesting correlations. All the excitatory agents i.e., ACh, AVP, OXY, and LHRH, have been indicated by intracerebral application studies to be facilitatory on lordosis. The inhibitory agent, 5HT, could inhibit lordosis, when applied to the VMN and its vicinity. Such correlations indicate that these transmitters and peptides can facilitate or inhibit lordosis by increasing or decreasing, respectively, the frequency of action potentials in the types of hypothalamic neurons recorded here.

Quantitative autoradiographic analysis of estradiol retention by cells in the preoptic area, hypothalamus and amygdala.

These experiments were done to compare quantitatively, on a cell-by-cell basis, estradiol retention by cells in the medial preoptic area, arcuate nucleus, ventrolateral subdivision of the ventromedial nucleus, and the caudal half of the medial nucleus of the amygdala. The steroid autoradiograms were prepared from 2 mu sections of brains from ovariectomized, adrenalectomized adult female rats that had been infused intravenously with [3H] estradiol (E2) in a regimen which kept circulating hormone concentration at or above proestrus levels for 3-4 h. Even in these brain regions, containing the most dense collections of E2-concentrating cells, a maximum of only 27-61% of the cells concentrated E2. Therefore, in these regions only a particular subset of the cells retain hormone; other cells in the region do not retain hormone. Frequency distribution histograms of the number of grains per cell versus the number of cells in each region showed a wide range in the amount of E2 retained per cell, and no modes among E2-retaining cells. The data followed a distribution markedly different from that predicted by a simple Poisson distribution, confirming that E2-retention does not result from a random, passive process such as diffusion. The overall quantitative characteristics of the frequency distribution histograms were similar across the four brain areas. Therefore, we propose that the different E2-sensitive functions of these brain areas must depend on differences in the neural connectivity or differences in hormone regulated peptide content of the areas.

Formation of behaviorally active estrogen in the dove brain: induction of preoptic aromatase by intracranial testosterone.

The preoptic area (POA) of the male ring dove is a target for specific behavioral effects of estrogen that are separable from those of androgen. Activity of the aromatase system in the POA, which converts testosterone to 17 beta-estradiol (E2), is increased by systemic androgen. Using crystalline steroid implants positioned stereotaxically in the brain, we examined whether aromatase induction is a result of direct steroid action on the POA, which can occur independently of the behavioral effects of androgen. Implants of testosterone propionate (TP) greater than 1.0 mm from POA nuclei were ineffective in increasing preoptic aromatase activity irrespective of whether the implants were unilateral, or bilateral with twice the potential output of testosterone. Within the 1.0-mm range, distance of implant from the POA nuclei was negatively correlated with induced aromatase activity in POA samples, indicating a direct effect of testosterone or its metabolites on enzyme activity. Induction of aromatase activity was higher in the right side of the POA than the left, suggesting asymmetry in inducible aromatase. Inactive 5 beta-reduced androstanes, 5 alpha-dihydrotestosterone and 17 beta-estradiol were formed from intracranial 3H-testosterone in POA. Since estradiol benzoate implants did not induce aromatase activity, this metabolite does not appear to act directly on the POA, although it is effective if administered systemically. Implants of TP in the region of the POA caused vocal behavior (perch calling) to be shown by some males. There was no correlation between the behavioral effectiveness of implants and induced POA aromatase activity. Since increase in E2 formation occurred in the absence of vocal behavior, activation of androgen-dependent behavior is not an absolute requirement for the induction effect. We conclude that testosterone can influence aromatase activity required for local production of E2 in the brain by direct action on POA cells.

Firing properties of cat basal forebrain neurones during sleep-wakefulness cycle

Neuronal activity was studied in the basal forebrain area (BFA) of freely moving cats during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS). Two classically synchronizing and hypnogenic regions, the preoptic area (POA) and the olfactory tubercle (OT) were explored by microelectrodes. Compared to W, the discharge rate in most of the POA cells was not modified or was slightly reduced by SWS, but it was increased by PS. Half of the OT cells increased slightly their firing frequency during falling asleep. A great proportion of OT neurones showed facilitation of activity during PS also, which in half of the cells started already in the last seconds of SWS. The results are discussed from the point of view of the synchronizing and hypnogenic influence attributed to POA and OT.