A Comprehensive Method To Quantify Adaptations by Male and Female Mice With Hot Flashes Induced by the Neurokinin B Receptor Agonist Senktide

Vasomotor symptoms (VMS; or hot flashes) plague millions of reproductive-aged men and women who have natural or iatrogenic loss of sex steroid production. Many affected individuals are left without treatment options because of contraindications to hormone replacement therapy and the lack of equally effective nonhormonal alternatives. Moreover, development of safer, more effective therapies has been stymied by the lack of an animal model that recapitulates the hot-flash phenomenon and enables direct testing of hypotheses regarding the pathophysiology underlying hot flashes. To address these problems, we developed a murine model for hot flashes and a comprehensive method for measuring autonomic and behavioral thermoregulation in mice. We designed and constructed an instrument called a thermocline that produces a thermal gradient along which mice behaviorally adapt to a thermal challenge to their core body temperature set point while their thermal preference over time is tracked and recorded. We tested and validated this murine model for VMS by administration of a TRPV1 agonist and a neurokinin B receptor agonist, capsaicin and senktide, respectively, to unrestrained mice and observed their autonomic and behavioral responses. Following both treatments, the mice exhibited a VMS-like response characterized by a drop in core body temperature and cold-seeking behavior on the thermocline. Senktide also caused a rise in tail skin temperature and increased Fos expression in the median preoptic area, a hypothalamic temperature control center. This dynamic model may be used to fully explore the cellular and molecular bases for VMS and to develop and test new therapeutic options.

A microsomal based method to detect aromatase activity in different brain regions of the rat using ultra performance liquid chromatography-mass spectrometry

Aromatase (ARO) is a cytochrome P450 enzyme that accounts for local estrogen production in the brain. The goal of this study was to develop a microsomal based assay to sensitively and reliably detect the low levels of ARO activity in different brain regions. Enzyme activity was detected based on the conversion of testosterone to estradiol. Quantity of estradiol was measured using ultra performance liquid chromatography-mass spectrometry. Detection was linear over a range of 2.5-200pg/ml estradiol, and was reproducible with intra- and inter-assay coefficients of variation (CV) <15%. Estradiol production using isolated microsomes was linear with time up to 30min as well as linearly related to amount of microsome. Substrate concentration curves revealed enzymatic kinetics (hippocampus: Vmax and Km: 0.57pmol estradiol/h per mg microsome and 48.58nM; amygdala: Vmax and Km: 1.69pmol estradiol/h per mg microsome and 48.4nM; preoptic area: Vmax and Km: 0.96pmol estradiol/h per mg microsome and 44.31nM) with testosterone used at a saturating concentration of 400nM. Anastrozole treatment blocked ARO activity in hippocampal and ovarian microsomes, indicating that the assay is specific for ARO. Also, we showed that the distribution of the long form ARO mRNA (CYP19A1) in different regions of the brain is correlated with ARO activity, with highest levels in the amygdala, followed by preoptic area and hippocampus. In the frontal cortex, very little long form ARO mRNA, and little to no ARO activity, were detected. These findings demonstrate that the microsomal incubation (MIB) assay is a sensitive and reliable method for quantifying ARO activity in discrete brain regions.

Effects of Fluoxetine Administration on Regional Galanin Expression in Obese Zucker Rat Hypothalamus

The aim of the present work was to study the potential involvement of hypothalamic galanin system in the anorectic mechanism of fluoxetine in obese Zucker rats. Male obese Zucker (fa/fa) rats were administered fluoxetine (10 mg/kg; i.p.) daily for two weeks. The control group was given 0.9% NaCl solution. Significant decreases in food intake, final body weight and total body fat were observed after fluoxetine treatment. Although fluoxetine-treated rats showed a decrease in urine elimination, this effect was not enough to compensate decreased water intake, leading to dehydration, as showed by decreased body water content. Chronic fluoxetine administration increased the numbers of galanin positively immunostained neural cells in medial and lateral preoptic areas, lateral hypothalamic area and paraventricular nucleus (rostral and magnocellular regions), without changes in dorsomedial, ventromedial, supraoptic, suprachiasmatic and arcuate nuclei. Taken into account that galanin stimulates appetite, these results could represent rather a compensatory response against reduced food intake than a direct anorectic mechanism. Changes in the magnocellular region of the hypothalamic paraventricular nucleus suggest a role for galanin neural circuits at this level in fluoxetine-induced hydro-osmotic impairment.

GFAP Expression in Astrocytes of Suprachiasmatic Nucleus and Medial Preoptic Area are Differentially Affected by Malnutrition during Rat Brain Development

The aim of the present study was investigate, in young rats, the effects of malnutrition on astrocyte distribution of two hypothalamic regions, the circadian pacemaker suprachiasmatic nucleus (SCN) and the medial preoptic area (MPA). Control rats were born from mothers fed on commercial diet since gestation and malnourished rats from mothers fed on multideficient diet, from the beginning of gestation (GLA group) or from the onset of lactation (LA group). After weaning, pups received ad libitum the same diet as their mothers, and were maintained under a 12/12 h light/dark cycle. The animals were analyzed either at 30-33, or 60-63 days of life. Brain coronal sections (50 microm) were processed to visualize glial fibrillary acidic protein (GFAP) immunoreactivity. Compared to control rats, both malnourished groups of 30 and 60 days exhibited a reduced number of GFAP-immunoreactive astrocytes in the SCN. The total GFAP-immunoreactive area in the SCN of the GLA group differed from the control group at both age ranges analyzed. The GFAP expression as measured by the relative optical density (ROD) exhibited a 50-60% reduction in the MPA in both malnourished groups, compared to controls. The results suggest that malnutrition early in life leads to alterations in gliogenesis or glial cell proliferation in both nuclei, being these alterations greater in the MPA. Compensatory plasticity mechanisms in the GFAP-expression seem to be developed in the astrocyte differentiation process in the SCN, especially when the malnutrition is installed from the lactation.

Resonance micro-Raman investigations of the rat medial preoptic nucleus: effects of a low-iron diet on the neuroglobin content

The aim of this study was to investigate the medial preoptic nucleus (MPN) of the anterior hypothalamus by resonance Raman spectroscopy (514.5 nm) to determine if it is possible to enhance the Raman scattering of hemoproteins in fresh brain tissue slices. The resonance effect was compared with near-infrared Raman spectra. Two groups of male Sprague Dawley rats were studied, one control group on a normal diet and one group on a low-iron diet to evoke iron deficiency. Each group consisted of four rats, 38-41 days old. The diets lasted for 11, 12, and 15 days. The MPN regions of brain tissue slices were analyzed by monitoring raw and pre-processed mean data, by cluster analysis, and by deriving difference spectra from pre-processed mean spectra. Cluster analysis of the resonance Raman spectra could identify different hemoprotein groups, namely, hemoglobin (Hb) and neuroglobin (Ngb). Spectra from randomly distributed spots revealed high Hb content, whereas Ngb was evenly distributed in the MPN. The different spectra showed a decrease of the Ngb and lipid content for the animals on the low-iron diet. The Ngb decrease was approximately 20%. The data show that resonance Raman spectroscopy is well suited to study hemoproteins in fresh brain tissue.

Morphological evidence for direct interaction between kisspeptin and gonadotropin-releasing hormone neurons at the median eminence of the male goat: an immunoelectron microscopic study

Kisspeptin has been thought to play pivotal roles in the control of both pulse and surge modes of gonadotropin-releasing hormone (GnRH) secretion. To clarify loci of kisspeptin action on GnRH neurons, the present study examined the morphology of the kisspeptin system and the associations between kisspeptin and GnRH systems in gonadally intact and castrated male goats. Kisspeptin-immunoreactive (ir) and Kiss1-positive neurons were found in the medial preoptic area of intact but not castrated goats. Kisspeptin-ir cell bodies and fibers in the arcuate nucleus (ARC) and median eminence (ME) were fewer in intact male goats compared with castrated animals. Apposition of kisspeptin-ir fibers on GnRH-ir cell bodies was very rare in both intact and castrated goats, whereas the intimate association of kisspeptin-ir fibers with GnRH-ir nerve terminals was observed in the ME of castrated animals. Neurokinin B immunoreactivity colocalized not only in kisspeptin-ir cell bodies in the ARC but also in kisspeptin-ir fibers in the ME, suggesting that a majority of kisspeptin-ir fibers projecting to the ME originates from the ARC. A dual immunoelectron microscopic examination revealed that nerve terminals containing kisspeptin-ir vesicles made direct contact with GnRH-ir nerve terminals at the ME of castrated goats. There was no evidence for the existence of the typical synaptic structure between kisspeptin- and GnRH-ir fibers. The present results suggest that the ARC kisspeptin neurons act on GnRH neurons at the ME to control (possibly the pulse mode of) GnRH secretion in males.

Proteomic analysis of diaminochlorotriazine (DACT) adducts in three brain regions of Wistar rats

Atrazine (ATRA) is the most commonly applied herbicide in the United States and is detected frequently in drinking water at significant levels. Following oral exposure, metabolism of ATRA generates diaminochlorotriazine (DACT), an electrophilic molecule capable of forming covalent protein adducts. At high doses, both ATRA and DACT can disrupt the preovulatory luteinizing hormone (LH) surge in rats, thereby altering normal reproductive function. This research was designed to identify DACT protein adducts formed in three distinct brain regions of ATRA-exposed rats, including the preoptic area (POA), medial basal hypothalamus (MBH), and cortex (CTX). Proteins with DACT adducts were identified following 2-dimensional electrophoresis (2-DE), immunodetection, and MALDI-TOF mass spectrometry analysis. Western blots from exposed animals revealed over 30 DACT-modified spots that were absent in controls. Protein spots were matched to concurrently run 2-DE gels stained with Sypro Ruby, excised, and in-gel digested with trypsin.

Presence of beta-follicle-stimulating hormone and beta-luteinizing hormone transcripts in the brain of Cichlasoma dimerus (Perciformes: Cichlidae): effect of brain-derived gonadotropins on pituitary hormone release

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) play key roles in vertebrate gametogenesis and steroidogenesis. They are mainly synthesized in the pituitary gland. While investigating the ontogeny of FSH and LH cells in the cichlid fish Cichlasoma dimerus by immunohistochemistry (IHC), we unexpectedly found immunoreactive neurons in the preoptic area, sending their projections through different brain areas and neurohypophysis. Our previous work using Western blot and IHC techniques applied to the adult brain confirmed these findings. To further demonstrate the extrapituitary expression of these hormones, we performed RT-PCR detecting sequences coding for beta-FSH and beta-LH subunits in the C. dimerus pituitary and brain (preoptic-hypothalamic area). The expression of these transcripts in both organs was consistent with their peptide expression showing a high sequence homology when compared with other phylogenetically related fish. An individual pituitary in vitro culture system was utilized to study the possible modulatory effect of brain-derived gonadotropins on pituitary hormone secretion. Pituitary explants were cultured with different concentrations of LH or FSH, and the culture media were analyzed by Western blot. Exogenous LH produced a dose-dependent increase in pituitary beta-LH, beta-FSH and somatolactin (SL) releases. No effect was observed on growth hormone (GH). The effect on prolactin (PRL) was not consistent among treatments. Exogenous FSH produced an inhibition in beta-LH release, dose-dependent increases in beta-FSH and SL releases, and no effect on PRL and GH releases. These findings support the concept of regulation of pituitary trophic hormones by brain-derived gonadotropins.

Does nitric oxide act in the ventromedial preoptic area to mediate oestrogen negative feedback in the seasonally anoestrous ewe?

Seasonal anoestrus in the ewe results from enhanced oestrogen negative feedback. Recent data have implicated the ventromedial preoptic area (vmPOA) as an important site of oestrogen action. This study addressed whether NO acts within the vmPOA to inhibit LH during seasonal anoestrus. In Experiment 1, microimplants containingNω-nitro-l-arginine methyl ester (l-NAME, NOS inhibitor),S-methyl thiocitrulline (SMTC, neural NOS (nNOS) inhibitor) or empty implants (control) were administered during mid-anoestrus to the vmPOA.l-NAME, but not SMTC, significantly increased LH pulse frequency. For Experiment 2, ewes in late anoestrus were administered 7-nitroindazole (7NI; nNOS inhibitor),l-NAME, SMTC, or empty implants. 7NI, but notl-NAME or SMTC, increased LH pulse frequency. In Experiment 3, the effects of microimplants and microinjections ofl-NAME were compared in mid-anoestrus. Microinjections ofl-NAME (300 nl at 10 μg/μl) increased LH pulse frequency, but microimplants did not. In late anoestrus, similar microinjections were ineffective. Taken together, the results of Experiments 1–3 suggested that NO inhibition may be stronger during the middle than at the end of seasonal anoestrus. To test this hypothesis, ewes in Experiment 4 received microinjection ofl-NAME or vehicle thrice during the non-breeding season; none of the treatments increased LH pulse frequency. These results indicate that NO plays a role in the vmPOA in suppressing LH secretion during seasonal anoestrus because NOS inhibitors were consistently stimulatory when LH pulse frequency was low. However, the inconsistent and modest effects of these inhibitors suggest that NO actions in this area cannot completely account for the effects of inhibitory photoperiod.

Improvement in reproductive parameters in hypogonadal female mice by regulated gene replacement therapy in the central nervous system

One of the challenges of gene targeting is to achieve regulated transgene expression in specific target cells. The hypogonadal (hpg) mice are genetically deficient in hypothalamic gonadotropin-releasing hormone (GnRH) production due to a deletion in the GnRH gene, resulting in hypogonadotropic hypogonadism. Here we show an improvement in reproductive parameters of adult female homozygous hpg mice by direct infusion into the hypothalamic preoptic area (POA) of a herpes simplex virus (HSV)-based amplicon vector containing a 13.5 kb genomic fragment encoding the GnRH gene together with its cognate promoter and regulatory elements. Following vector injection, GnRH-expressing neurons were detected in the POA, and pituitary and plasma gonadotropin levels as well as ovarian and uterine weights increased. In addition, a subset of injected hpg mice demonstrated cyclic estrous changes, consistent with regulated control of GnRH production. Administration of kisspeptin-10 resulted in an increase in plasma luteinizing hormone levels, further supporting appropriate regulation of the introduced GnRH transgene. These findings indicate that delivery of the GnRH gene resulted in selective neuronal expression of GnRH and regulated hypothalamic GnRH release. To our knowledge, this is the first example of the correct targeting of a gene under its cognate promoter to neurons resulting in selective and regulated synthesis of a biologically active peptide, and thus may have a wide range of applications in the treatment of human disorders.

Pituitary atrial natriuretic peptide of paraventricular nucleus origin

Atrial natriuretic peptide-synthesizing neurons in the hypothalamic paraventricular nucleus constitute the major sources of ANP in the three lobes of the pituitary gland. Complete transection of the pituitary stalk eliminated 93% of ANP from the intermediate lobe, 47 and 77% from the anterior and the posterior lobes, respectively. Meantime, increased levels of immunoreactive ANP were measured in the median eminence, due to the accumulation of the peptide in the transected axons centrally to the transected stalk and in the paraventricular nucleus. It is likely that ANP neurons in the paraventricular nucleus innervate the pituitary, but those in the periventricular (median) preoptic nucleus and the organum vasculosum laminae terminalis may not contribute to the ANP innervation of the pituitary gland.

Alleviation of thermoregulatory dysfunction with the new serotonin and norepinephrine reuptake inhibitor desvenlafaxine succinate in ovariectomized rodent models

Hot flushes and night sweats, referred to as vasomotor symptoms (VMS), are presumed to be a result of declining hormone levels and are the principal menopausal symptoms for which women seek medical treatment. To date, estrogens and/or some progestins are the most effective therapeutics for alleviating VMS; however, these therapies may not be appropriate for all women. Therefore, nonhormonal therapies are being evaluated. The present study investigated a new reuptake inhibitor, desvenlafaxine succinate (DVS), in animal models of temperature dysfunction. Both models used are based on measuring changes in tail-skin temperature (TST) in ovariectomized (OVX) rats. The first relies on naloxone-induced withdrawal in morphine-dependent (MD) OVX rats, resulting in an acute rise in TST. The second depends on an OVX-induced loss of TST decreases during the dark phase as measured by telemetry. An initial evaluation demonstrated abatement of the rise in TST with long-term administration of ethinyl estradiol or with a single oral dose of DVS (130 mg/kg) in the MD model. Further evaluation showed that orally administered DVS acutely and dose dependently (10-100 mg/kg) abated a naloxone-induced rise in TST of MD rats and alleviated OVX-induced temperature dysfunction in the telemetry model. Oral administration of DVS to OVX rats caused significant increases in serotonin and norepinephrine levels in the preoptic area of the hypothalamus, a key region of the brain involved in temperature regulation. These preclinical studies provide evidence that DVS directly impacts thermoregulatory dysfunction in OVX rats and may have utility in alleviating VMS associated with menopause.

Hyperpolarization-activated cation channels are expressed in rat hypothalamic gonadotropin-releasing hormone (GnRH) neurons and immortalized GnRH neurons

OBJECTIVES

The current research was conducted to determine whether hyperpolarization-activated cyclic nucleotide-gated (HCN1-4) channels are expressed in gonadotropin-releasing hormone (GnRH) neurons in the female rat hypothalamus and immortalized GnRH neurons (GT1-7 cells).

METHODS

Double-label fluorescence immunohistochemistry was used to colocalize HCN1-4 channels and GnRH in GnRH neurons in the female rat hypothalamus. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunocytochemistry were used to analyze HCN channel gene expression in GT1-7 cells.

RESULTS

Double-label fluorescence immunohistochemistry showed that 43% of hypothalamic GnRH neurons immunostained for HCN2 and 90% of GnRH neurons immunostained for HCN3. RT-PCR and Western blot showed expression of all four HCN channel subunits in GT1-7 cells. Double-label immunocytochemistry showed cytoplasmic immunostaining of HCN2 and HCN3 in GT1-7 cells.

CONCLUSIONS

This study demonstrates for the first time that HCN channels are expressed in GnRH neurons in the rat hypothalamus and GT1-7 cells. Our research supports the hypothesis that HCN channels may be involved in electrical bursting activity and pulsatile GnRH secretion in endogenous GnRH neurons and GT1-7 cells.

The differential role of prostaglandin E2 receptors EP3 and EP4 in regulation of fever

The innate immune system of mammals is able to detect bacteria when they infect local tissue or enter the blood stream, and initiate an immediate immune response. Prostaglandin (PG) E2 is considered as the most important link between the peripheral immune system and the brain. Due to four PGE2 receptors (EP receptors) and their differential expression in various areas of the hypothalamus and brain stem, PGE2 mediates different components of the acute phase reaction. A fever model is discussed in which the preoptic area contains the mechanisms for both hyperthermic and hypothermic responses and EP receptors in the median preoptic area (MnPO) modulate the thermogenic system. The neuron-specific modulation of EP receptors in the MnPO can be critically tested by using Cre-recombinase-mediated DNA recombination in genetically engineered mice. A concept for mice with conditional expression of EP3R and EP4R to investigate the different roles of those receptors in lipopolysaccharide (LPS)-induced fever is presented.

Different neuronal populations of the rat median preoptic nucleus express c-fos during sleep and in response to hypertonic saline or angiotensin-II

The median preoptic nucleus (MnPN) of the hypothalamus contains sleep-active neurones, and sleep-related Fos-immunoreactivity (IR) in this nucleus is primarily expressed in GABAergic cells. The MnPN also contains cells responsive to hypertonic saline and to angiotensin-II (Ang-II). To clarify functional relationships between MnPN neurones involved in the regulation of sleep and body fluid homeostasis, we examined c-fos expression in the MnPN after administration of hypertonic saline and Ang-II in both spontaneously sleeping and sleep-deprived rats. Systemic administration of hypertonic saline and intracerebroventricular (i.c.v.) injection of Ang-II increased Fos-IR in both spontaneously sleeping and sleep-deprived rats, compared to control animals. To determine if the population of MnPN neurones activated in response to osmotic and hormonal stimuli is similar to or different from neurones activated during sleep, we quantified Fos-IR in MnPN GABAergic neurones in spontaneously sleeping hypertonic saline- and Ang-II-treated rats versus respective control rats. Fos-IR evoked by these treatments occurred primarily (80-85%) in non-GABAergic neurones. Findings of the present study provide evidence that separate populations of MnPN neurones are involved in the regulation of sleep and body fluid homeostasis.

Stress elevates corticotropin-releasing factor (CRF) and CRF-binding protein mRNA levels in rainbow trout (Oncorhynchus mykiss)

The objectives of this study were to characterize rainbow trout (Oncorhynchus mykiss) corticotropin-releasing factor (CRF)-binding protein (CRF-BP) cDNA and to examine the variations in CRF-BP and CRF mRNA levels in response to different intensities of stress. Trout were physically disturbed by a single or three consecutive periods of chasing until exhaustion followed by 2 h of recovery. The pituitary CRF-BP and preoptic area CRF1 mRNA contents were significantly increased only after repeated chasing events. Physical disturbance increased plasma cortisol levels with the largest change occurring in the group of trout that were exposed to repeated chasing events. Trout were also individually isolated in 120 l tanks or confined to 1.5 l boxes for 4, 24 or 72 h. CRF-BP mRNA levels in confined fish were greater than those of isolated fish at 72 h although there were no differences compared with the control group. CRF1 mRNA levels in the preoptic area were greater and remained elevated for a longer period in confined compared with isolated trout. Isolation led to a transient increase in plasma cortisol levels, but the higher cortisol values developed in the confined fish suggest that this treatment was more stressful than isolation. These results demonstrate that the intensity and duration of stress are important factors regulating CRF and CRF-BP mRNA levels in rainbow trout. We hypothesize that pituitary CRF-BP is involved in regulating the activity of the stress axis, possibly by reducing access to CRF1 receptors in the corticotropes.

Dual-phenotype GABA/glutamate neurons in adult preoptic area: sexual dimorphism and function

It is generally assumed that the inhibitory neurotransmitter GABA and the stimulatory neurotransmitter glutamate are released from different neurons in adults. However, this tenet has made it difficult to explain how the same afferent signals can cause opposite changes in GABA and glutamate release. Such reciprocal release is a central mechanism in the neural control of many physiological processes including activation of gonadotropin-releasing hormone (GnRH) neurons, the neural signal for ovulation. Activation of GnRH neurons requires simultaneous suppression of GABA and stimulation of glutamate release, each of which occurs in response to a daily photoperiodic signal, but only in the presence of estradiol (E2). In rodents, E2 and photoperiodic signals converge in the anteroventral periventricular nucleus (AVPV), but it is unclear how these signals differentially regulate GABA and glutamate secretion. We now report that nearly all neurons in the AVPV of female rats express both vesicular glutamate transporter 2 (VGLUT2), a marker of hypothalamic glutamatergic neurons, as well as glutamic acid decarboxylase and vesicular GABA transporter (VGAT), markers of GABAergic neurons. These dual-phenotype neurons are the main targets of E2 in the region and are more than twice as numerous in females as in males. Moreover, dual-phenotype synaptic terminals contact GnRH neurons, and at the time of the surge, VGAT-containing vesicles decrease and VGLUT2-containing vesicles increase in these terminals. Thus, we propose a new model for ovulation that includes dual-phenotype GABA/glutamate neurons as central transducers of hormonal and neural signals to GnRH neurons.

Neonatal handling and reproductive function in female rats

Neonatal handling induces anovulatory estrous cycles and decreases sexual receptivity in female rats. The synchronous secretion of hormones from the gonads (estradiol (E2) and progesterone (P)), pituitary (luteinizing (LH) and follicle-stimulating (FSH) hormones) and hypothalamus (LH-releasing hormone (LHRH)) are essential for the reproductive functions in female rats. The present study aimed to describe the plasma levels of E2 and P throughout the estrous cycle and LH, FSH and prolactin (PRL) in the afternoon of the proestrus, and the LHRH content in the medial preoptic area (MPOA), median eminence (ME) and medial septal area (MSA) in the proestrus, in the neonatal handled rats. Wistar pup rats were handled for 1 min during the first 10 days after delivery (neonatal handled group) or left undisturbed (nonhandled group). When they reached adulthood, blood samples were collected through a jugular cannula and the MPOA, ME and MSA were microdissected. Plasma levels of the hormones and the content of LHRH were determined by RIA. The number of oocytes counted in the morning of the estrus day in the handled rats was significantly lower than in the nonhandled ones. Neonatal handling reduces E2 levels only on the proestrus day while P levels decreased in metestrus and estrus. Handled females also showed reduced plasma levels of LH, FSH and PRL in the afternoon of the proestrus. The LHRH content in the MPOA was significantly higher than in the nonhandled group. The reduced secretion of E2, LH, FSH and LHRH on the proestrus day may explain the anovulatory estrous cycle in neonatal handled rats. The reduced secretion of PRL in the proestrus may be related to the decreased sexual receptiveness in handled females. In conclusion, early-life environmental stimulation can induce long-lasting effects on the hypothalamus-pituitary-gonad axis.

Experimental study of the connections of the telencephalon in the rainbow trout (Oncorhynchus mykiss). II: Dorsal area and preoptic region

In this study and the accompanying article (Folgueira et al., 2004a), the fluorescent carbocyanine dye 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used in fixed tissue to comprehensively analyze the connections of the different regions of the telencephalic lobes and the preoptic region of the rainbow trout. Here, we analyze the connections of the dorsal area (D; pallium) of the telencephalon, and the preoptic region, as well as the telencephalic connections of several structures in the diencephalon and brainstem of juvenile trout. The dorsal plus dorsolateral pallial zone of D (Dd+Dl-d) receives afferents from contralateral Dd+Dl-d, the ventral area of the telencephalon, preoptic nucleus, suprachiasmatic nucleus, medial thalamus, preglomerular complex, anterior and lateral tuberal nuclei, posterior tuberal nucleus, posterior hypothalamic lobe, superior raphe nucleus, and the rhombencephalic central gray and reticular formation, and projects to the central zone of D (Dc), medial thalamus, and some caudomedial hypothalamic regions. The medial zone of D (Dm) maintains reciprocal connections with the preglomerular complex and also receives afferents from the preoptic nucleus, suprachiasmatic nucleus, anterior tuberal nucleus, preglomerular tertiary gustatory nucleus, posterior tubercle, superior raphe nucleus, locus coeruleus, and the rhombencephalic central gray, and reticular formation. Dc receives fibers mainly from Dd+Dl-d, preoptic nucleus, preglomerular complex, and torus semicircularis and projects to several extratelencephalic centers, including the paracommissural nucleus, optic tectum, torus semicircularis, thalamus, preglomerular complex, posterior tubercle nuclei, and inferior hypothalamic lobes. The posterior zone of D (Dp) is mainly connected with the olfactory bulbs, the ventral and supracommissural nuclei of the ventral area (subpallium), the preoptic nucleus, and the preglomerular complex and projects to wide hypothalamic and posterior tubercular regions. The preoptic nucleus projects to the olfactory bulb, to most regions of the telencephalic lobes, and to several diencephalic and brainstem structures. These results reveal complex and specialized connectional patterns in the rainbow trout dorsal telencephalon and preoptic region. Most of these connections have not been described previously in salmonids. These connections indicate that the salmonid telencephalon is involved in multisensorial processing and modulation of brain activity.

Changes of body temperature and extracellular serotonin level in the preoptic area and anterior hypothalamus after thermal or serotonergic pharmacological stimulation of freely moving rats

Although many studies has been shown that serotonin (5-HT) in the preoptic area and anterior hypothalamus (PO/AH) is important for regulating body temperature (Tb), the exact role is not established yet due to conflicting results probably related to experimental techniques or conditions such as the use of anesthesia. The purpose of present study was to clarify the role of 5-HT in the PO/AH using the combined methods of telemetry, microdialysis and high performance liquid chromatography (HPLC), with a special emphasis on the regulation of Tb in freely moving rats. Firstly, we measured changes in Tb and levels of extracellular 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the PO/AH during cold (5 degrees C) and heat (35 degrees C) exposure. We also perfused fluoxetine (5-HT re-uptake inhibitor) and 8-hydroxy-2-(Di-n-propylamino)tetralin (8-OH-DPAT: 5-HT1A agonist) into the PO/AH. During both exposures, although Tb changed significantly, no significant changes were noted in extracellular levels of 5-HT and 5-HIAA in the PO/AH. In addition, although perfusion of fluoxetine or 8-OH-DPAT into the PO/AH increased or decreased extracellular 5-HT and 5-HIAA levels in the PO/AH respectively, but Tb did not change at all. Our results suggest that 5-HT in the PO/AH may not mediate acute changes in thermoregulation.

Serotonergic collateralized projections from Barrington's nucleus to the medial preoptic area and lumbo-sacral spinal cord

In this study, we employed triple fluorescent labelling to reveal the distribution of the direct serotonergic neurons within Barrington's nucleus (BN) that supply branching collateral input to the medial preoptic area (MPA) and to the lumbo-sacral spinal cord (LSC). Immunocytochemical detection of the monoclonal antibody raised against serotonin was used for identification of the neurons. The projections were defined by injections of two retrograde tracers: fluoro gold and rhodamine in the MPA and LSC, respectively. The aim of this study is to identify the direct projections to BN and MPA and/or LSC. The present study confirms findings of others describing BN-LSC projections and extends previous findings by demonstrating an single or collateralized fibers with MPA, and serotonergic immunoreactive fibers.

Localization, expression and control of adrenocorticotropic hormone in the nucleus preopticus and pituitary gland of common carp (Cyprinus carpio L.)

Adrenocorticotropic hormone (ACTH) takes a central role in the hypothalamo-pituitary-interrenal axis (HPI axis), which is activated during stress. ACTH is produced by the corticotrope cells of the pituitary pars distalis (PD) and is under control of factors from the nucleus preopticus (NPO). The distribution of ACTH in the hypothalamo-pituitary system in common carp (Cyprinus carpio L.) was assessed by immunohistochemistry. ACTH and beta-endorphin immunoreactivity was observed in the ACTH cells in the PD and in the NPO. Nerve fibers, originating from the NPO and projecting to the pituitary gland, contain beta-endorphin, but not ACTH, and these fibers either control the pituitary pars intermedia (PI) through beta-endorphin or release it to the blood. The release of pituitary ACTH (studied in a superfusion setup) must in vivo be under predominant inhibitory control of dopamine. Release of ACTH is stimulated by corticotropin-releasing hormone, but only when ACTH cells experience dopaminergic inhibition. The expression of the precursor pro-opiomelanocortin in (POMC) NPO, PD and PI was studied in an acute restraint stress paradigm by real-time quantitative polymerase chain reaction (RQ-PCR). POMC gene expression is upregulated in these three key tissues of the hypothalamo-pituitary complex, revealing a hitherto unforeseen complex role for POMC-derived peptides in the regulation of responses to stress.

FOS expression in orexin neurons following muscimol perfusion of preoptic area

Unilateral microdialysis-perfusion of the preoptic area with 50 microM muscimol decreased the sleep period of rats to less than 3% of the baseline value over a 90 min period before death (p = 0.018 by Wilcoxon signed-rank test). These rats showed the expression of FOS in 36% of the orexin neurons located in the perifornical/lateral hypothalamic areas on the side ipsilateral to the perfusion site, but in only 3% of the orexin neurons on the side contralateral to it (p = 0.018 by Wilcoxon signed-rank test). These results suggest that subpopulations of the preoptic neurons give an inhibitory tone to the activities of the orexin neurons in the perifornical/lateral hypothalamic areas.

The 26S proteasome participates in the sequential inhibition of estrous behavior induced by progesterone in rats

Estrous behavior induced by progesterone (P) treatment of estradiol-primed rats is followed by a period in which females do not respond behaviorally to a second administration of P [sequential inhibition (SI)]. SI is thought to involve P-dependent down-regulation of hypothalamic P receptor (PR) content. This study tested the hypothesis that the 26S proteasome participates in the regulation of SI and brain PR content in female rats. Ovariectomized, estrogen-primed (estradiol benzoate, 2 microg s.c.) adult rats were injected with P (1 mg s.c.) alone or P with the proteasome inhibitors Z-Ile-Glu (OBu(1))-Ala-Leu-H (PSI, 300 microg/100 g s.c.) or N alpha-tosyl-lysyl chloromethyl ketone (TLCK, 200 microg i.p.) administered 48 h after estradiol priming. Sexual behavior was assessed in all animals 4 h later. These two agents inhibit 26S proteasome-mediated protein degradation by different mechanisms. To explore SI, the animals received a second P injection 24 h after the first, and a second sexual behavior test was performed 4 h later. After this test, brains were excised, and proteins were extracted from the preoptic area and the hypothalamus and processed for semiquantitative immunoblotting. In the first sexual behavior test (facilitation test), all animals treated with estradiol + P exhibited intense lordosis behavior. In the second sexual behavior test (inhibition test), both lordosis and proceptivity were significantly reduced in response to the second administration of P (SI). The magnitude of SI was significantly attenuated by the administration of either PSI or TLCK concurrently with the first P injection. The first P injection reduced PR content in the hypothalamus but not in the preoptic area. In contrast, PSI and TLCK significantly increased PR content in both structures. Our results suggest that PR degradation by the 26S proteasome participates in the expression of P-induced SI in female rats.

Activation of c-fos in GABAergic neurones in the preoptic area during sleep and in response to sleep deprivation

Neurones in the median preoptic nucleus (MnPN) and the ventrolateral preoptic area (vlPOA) express immunoreactivity for c-Fos protein following sustained sleep, and display elevated discharge rates during both non-REM and REM sleep compared to waking. We evaluated the hypothesis that MnPN and vlPOA sleep-active neurones are GABAergic by combining staining for c-Fos protein with staining for glutamic acid decarboxylase (GAD). In a group of six rats exhibiting spontaneous total sleep times averaging 82.2 +/- 5.1% of the 2 h immediately prior to death, >75% of MnPN neurones that were Fos-immunoreactive (IR) were also GAD-IR. Similar results were obtained in the vlPOA. In a group of 11 rats exhibiting spontaneous sleep times ranging from 20 to 92%, the number of Fos + GAD-IR neurones in MnPN and vlPOA was positively correlated with total sleep time. Compared to control animals, Fos + GAD-IR cell counts in the MnPN were significantly elevated in rats that were sleep deprived for 24 h and permitted 2 h of recovery sleep. These findings demonstrate that a majority of MnPN and vlPOA neurones that express Fos-IR during sustained spontaneous sleep are GABAergic. They also demonstrate that sleep deprivation is associated with increased activation of GABAergic neurones in the MnPN and vlPOA.