Basal Hypothalamus Research Articles

The dendron and episodic neuropeptide release.

The unexpected observation that the long processes of gonadotrophin-releasing hormone (GnRH) neurons not only conducted action potentials, but also operated to integrate afferent information at their distal-most extent gave rise to the concept of a blended dendritic-axonal process termed the "dendron". The proximal dendrites of the GnRH neuron function in a conventional manner, receiving synaptic inputs and initiating action potentials that are critical for the surge mode of GnRH secretion. The distal dendrons are regulated by both classical synapses and volume transmission and likely operate using subthreshold electrotonic propagation into the nearby axon terminals in the median eminence. Evidence indicates that neural processing at the distal dendron is responsible for the pulsatile patterning of GnRH secretion. Although the dendron remains unique to the GnRH neuron, data show that it exists in both mice and rats and may be a common feature of mammalian species in which GnRH neuron cell bodies do not migrate into the basal hypothalamus. This review outlines the discovery and function of the dendron as a unique neuronal structure optimised to generate episodic neuronal output.

Neuroendocrine Mechanisms Regulating Reproductive Transition in the Ruminant Female: Is KNDy Required?

Abstract States of reproductive transition in female livestock represent important and economically significant periods of physiological change that have major impacts on the efficiency and success of breeding and production programs. These include, but are not limited to, the process of sexual maturation, postpartum resumption of ovarian cycles, and cyclical recrudescence in seasonal breeding species. Over the last four decades, our laboratory has focused primarily on determining the fundamental neuroendocrine mechanisms controlling states of reproductive transition in bovine and equine models, and applying principals learned to develop managerial approaches for positive intervention. The objectives of this presentation are to briefly review our understanding of external and internal signaling pathways that regulate two of these transitional states in the bovine female, postpartum resumption of ovulatory cycles and pubertal development. The focus will be to consider contrasts and commonalities of hypothalamic-pituitary signaling pathways that govern the temporal trajectories of these processes, with particular emphasis on those pathways that modulate the GnRH pulse generator. Notably (and until recently), the pulse generator has been a poorly defined “black box” with respect to its cellular origin and neurochemical character. Thus, the synchronous pattern of GnRH neuronal depolarization, multiunit electrical activity, and release of GnRH for the control of gonadotropins have been accepted as intrinsic features of GnRH neurons themselves. However, the identification of the neuropeptide kisspeptin in 1996, and more recently (2007) the description of a specialized population of kisspeptin-secreting neurons in the medial basal hypothalamus, termed KNDy neurons, have provided convincing evidence for an extrinsic source of pulse generation within the arcuate/infundibular region. How do KNDy neurons serve in this function, what is their role in transducing environmental, nutritional, and behavioral signals during transitional states, and what is the potential for neuropeptides of KNDy neuron origin to serve as pharmacological agents to control reproduction?

Early Treatment of Hypothalamic Hypogonadism With LH-RH Analog Improved the Long-Term Prognosis of Hypogonadism of Adult-Onset Craniopharyngioma

Object: Craniopharyngiomas frequently grow on the cisternal surface of the hypothalamic region. The survival rate for childhood craniopharyngioma has been improving with more long-term survivors. Long-term survivors of childhood craniopharyngioma suffer a number of impairments, which include visual loss, endocrinopathy, hypothalamic dysfunction, cerebrovascular problems, neurologic and neurocognitive dysfunction. GnRH neurons in hypothalamus that send axons to portal blood system in median eminence fire in coordinated, repetitive, episodic manner, producing distinct pulses of GnRH in the portal blood system. In 2001, we experienced the case of hypothalamic hypogonadism after the radical surgery of craniopharyngioma located in the right basal ganglia and hypothalamus. During the operation, pituitary gland and stalk were preserved. The patient had developed panhypopituitarism and hypothalamic hypogonadism after transcranial surgery. The diagnosis of oligospermia and asthenospermia was made. We hypothesized that the hypogonadism was due to the lack of distinct pulses of GnRH after the surgery. The aim of this program was to demonstrate the efficacy of the pulsatile subcutaneous LH-RH therapy for the recovery of gonadal function from hypothalamic hypogonadism and to observe the long-term prognosis after recovery.Method: After a diagnosis of hypothalamic hypogonadism, low dose LH-RH treatment was given to a 29-year-old male with small portable automatically-timed infusion pump, connected to a subcutaneous (s.c.) catheter. Gonadorelin acetate was prepared to the concentration of 0.8mg/ml. Sixteen micrograms of LH-RH s.c. was given every 120 min. Serum levels of gonadotropin and testosterone were monitored. The treatment was continued until his gonadal function normalized. Long-term follow up was continued after low dose LH-RH treatment.Result: After the six months of pulsatile LH-RH treatment, serum level of testosterone turned normal. Then the treatment was paused in 2003. His wife became pregnant with in-vitro fertilization (IVF) in 2007 and gave birth in 2008. Moreover, his wife became pregnant naturally without IVF in 2009 and gave birth in 2010, suggesting the recovery from oligospermia and asthenospermia of her husband. Early recovery from hypothalamic hypogonadism maintained normal gonadal function in 2020.Clinical Lessons: We demonstrated a case of successful treatment of the hypothalamic hypogonadism after the surgery of craniopharyngioma. The pulsatile subcutaneous LH-RH therapy is efficacious for the case with the lack of the distinct pulses of GnRH after radical surgery of craniopharyngioma. Early treatment of hypothalamic hypogonadism with LH-RH analog improved the long-term prognosis of hypogonadism of adult-onset craniopharyngioma.

Medial Parabrachial Nucleus Is Essential in Controlling Wakefulness in Rats.

Activation of the parabrachial nucleus (PB) in the brainstem induced wakefulness in rats, suggesting which is an important nucleus that controls arousal. However, the sub-regions of PB in regulating sleep-wake cycle is still unclear. Here, we employ chemogenetics and optogenetics strategies and find that activation of the medial part of PB (MPB), but not the lateral part, induces continuous wakefulness for 10 h without sleep rebound in neither sleep amount nor the power spectra. Optogenetic activation of glutamatergic MPB neurons in sleeping rats immediately wake rats mediated by the basal forebrain (BF) and lateral hypothalamus (LH), but not the ventral medial thalamus. Most importantly, chemogenetic inhibition of PB neurons decreases wakefulness for 10 h. Conclusively, these findings indicate that the glutamatergic MPB neurons are essential in controlling wakefulness, and that MPB-BF and MPB-LH pathways are the major neuronal circuits.

Neurobiology of sleep (Review)

Sleep is a physiological global state composed of two different phases: Non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. The control mechanisms of sleep manifest at the level of genetic, biological and cellular organization. Several brain areas, including the basal forebrain, thalamus, and hypothalamus, take part in regulating the activity of this status of life. The signals between different brain regions and those from cortical areas to periphery are conducted through various neuromediators, which are known to either promote wakefulness or sleep. Among others, serotonin, norepinephrine, histamine, hypocretin (orexin), acetylcholine, dopamine, glutamate, and gamma-aminobutyric acid are known to orchestrate the intrinsic mechanisms of sleep neurobiology. Several models that explain the transition and the continuity between wakefulness, NREM sleep and REM sleep have been proposed. All of these models include neurotransmitters as ligands in a complex reciprocal connectivity across the key-centers taking part in the regulation of sleep. Moreover, various environmental cues are integrated by a central pacemaker-located in the suprachiasmatic nucleus-which is able to connect with cortical regions and with peripheral tissues in order to promote the sleep-wake pattern.

Neuro-pharmacological reinstatement of ovulation and associated neurobiology in a macaque model of functional hypothalamic amenorrhoea.

What is the underlying neuropathology in a cynomolgus macaque model of functional hypothalamic amenorrhoea (FHA) and can it be normalized to restore ovulation? Anovulatory monkeys exhibited increased hypothalamic norepinephrine (NE), kisspeptin and gonadotropin-releasing hormone (GnRH) in the early follicular phase, but administration of the NE reuptake inhibitor (NRI), reboxetine (REB), restored ovulation during stress and normalized NE, kisspeptin and GnRH. Female cynomolgus macaques, like women, show individual reproductive sensitivity to modest psychosocial and metabolic stress. During stress, resilient females ovulate through two menstrual cycles whereas stress-sensitive (SS) macaques immediately cease ovulation. On Day 5 of a non-stressed menstrual cycle, resilient macaques have less NE synthesizing enzyme [dopamine β-hydroxylase (DBH)], kisspeptin and GnRH innervation of the medial basal hypothalamus but more endogenous serotonin than SS macaques. Stress increased DBH/NE, kisspeptin and GnRH but did not alter serotonin. In a longitudinal design, 27 adult (7-13 years) female cynomolgus macaques (Macaca fascicularis) with three different levels of sensitivity to stress were monitored with daily vaginal swabs and frequent serum progesterone (P) measurements. Three 90-day experimental periods called 'Cycle Sets' were monitored. A Cycle Set consisted of one ovulatory menstrual cycle without stress, and two cycles, or 60 days, with modest stress. Each Cycle Set was followed by a rest period. During a Cycle Set, individuals were either untreated (placebo) or administered escitalopram (CIT) or REB. Ultimately, half of each sensitivity group was euthanized during stress with CIT or REB treatment and the hypothalamus was obtained. Neurobiological endpoints were compared between CIT and REB treatment groups in stress resilient and SS monkeys. The monkeys were housed at the University of Pittsburgh primate facility for the duration of the experiments. Upon euthanasia, their brains and serum samples were shipped to the Oregon National Primate Research Center. The hypothalamus was examined with immunohistochemistry for the expression of DBH (a marker for NE axons), kisspeptin and GnRH. P was measured in the serum samples by radioimmunoassay. Daily administration of REB restored ovulation in 9 of 10 SS animals during stress. Of note, REB significantly increased P secretion during stress in the most sensitive group (P = 0.032), which indicates ovulation. CIT lacked efficacy. REB significantly reduced DBH/NE, kisspeptin and GnRH axon density in the hypothalamus relative to CIT treatment (P = 0.003. 0.018 and 0.0001, respectively) on Day 5 of the menstrual cycle in resilient and sensitive groups. N/A. The US FDA has not approved REB for human use, although it is used in Europe for the treatment of depression/anxiety as EdronaxTR. Whether REB could be useful for the treatment of FHA in women has not been determined. The use of an NRI to treat FHA is a novel approach and the potential reinstatement of ovulation could be straightforward compared to current treatment protocols. The underlying neurobiology provides a compelling case for treating the origin of the pathology, i.e. elevated NE, rather than circumventing the hypothalamus altogether with gonadotropins, which have associated risks such as hyperstimulation syndrome or multiple births. Portions of this study were supported by NIH grant HD062864 to C.L.B., NIH grant HD62618 to J.L.C. and C.L.B. and 1P51 OD011092 for the operation of the Oregon National Primate Research Center. There were no competing interests.

Dysregulated appetitive leptin signaling in male rodent offspring from post-bariatric dams.

Bariatric surgery produces significant positive benefits to recipients such as resolution of various obesity-related comorbidities, including improved reproductive function. Females of childbearing age seek bariatric surgical remedies to improve their chance of successful pregnancy; however, limited knowledge exists on the impact of surgical weight loss to subsequently born offspring.We previously reported that circulating leptin levels were reduced in pregnant females having previously received vertical sleeve gastrectomy (VSG) in comparison to control dams having received Sham surgery. Furthermore, the levels of leptin receptors in the VSG placenta were also reduced in comparison to controls in. These data suggest there may be a significant difference in leptin signaling during pregnancy that may produce an altered developmental environment for the offspring.Here, we investigate the adult offspring of dams having received VSG or Sham-VSG prior to pregnancy. Endogenous fasting plasma leptin levels were not different between Sham and VSG offspring. Fasting leptin receptor mRNA in the medial basal hypothalamus (MBH) was elevated in VSG offspring in comparison to Sham. Intraperitoneal administration of exogenous leptin produced reductions in acute food intake in male Sham offspring, but did not reduce food intake at any time point measured in male VSG offspring. Using Western blot, we identified elevated pSTAT3 and pSTAT3/STAT3 ratios in the MBH of post-VSG offspring in comparison to controls. Using immunohistochemistry, we found an increased number of pSTAT positive cells in the arcuate nucleus in the Sham offspring in comparison to VSG. In contrast, within the paraventricular and ventromedial hypothalamic nuclei the VSG offspring had elevated numbers of pSTAT-positive cells in comparison to controls. Collectively, these data support our hypothesis that leptin signaling is dysregulated in VSG offspring and may be partially responsible for the long-term impact of maternal bariatric surgery on the metabolic health of offspring.

Chronic alcohol exposure reduces acetylated histones in the sleep-wake regulatory brain regions to cause insomnia during withdrawal

BackgroundAlcohol use disorder (AUD) develops after chronic and heavy use of alcohol. Insomnia, a hallmark of AUD, plays a crucial role in the development of AUD. However, the causal mechanisms are unknown. Since chronic alcohol reduces acetylated histones and disrupts the epigenome, we hypothesized that chronic alcohol exposure will reduce acetylated histones in wake-promoting regions of the brain to cause insomnia during alcohol withdrawal. MethodsAdult male C57BL/6J mice, surgically instrumented for electrophysiological monitoring of sleep-wakefulness, were exposed to chronic alcohol (6.8%) consumption using Lieber-DeCarli liquid diet. Three experiments were performed. First, the effect of chronic alcohol consumption was examined on sleep-wakefulness during 7 days of withdrawal. Second, the expression of acetylated histones, H3 lysine 14 (AcH3K14), was examined in two major sleep-wake regulatory brain regions: basal forebrain (BF) and lateral hypothalamus (LH) of the brain by using western blotting. Next, blockade of histone deacetylase, via systemic administration of TSA was examined on alcohol-induced changes in sleep-wakefulness. ResultsAlcoholic mice displayed a significant reduction in the quality and quantity of NREM sleep coupled with a significant increase in wakefulness that lasted for several days during alcohol withdrawal. In addition, alcoholic mice displayed a significant reduction in the expression of AcH3K14 in both BF and LH. Systemic administration of TSA significantly attenuated insomnia and improved the quality and quantity of sleep during alcohol withdrawal. ConclusionsBased on our results, we suggest that a causal relationship exists between reduced histone acetylation and insomnia during alcohol withdrawal.

Estradiol and the feeding state modulate the interaction between leptin and the nitrergic system in female rats

Leptin mediates the interaction between reproductive function and energy balance. However, leptin receptors are not expressed in neurons that produce gonadotropin-releasing hormone (GnRH), likely indicating an indirect action through interneurons. Among likely neurons that modulate the secretion of GnRH are NO (nitric oxide) neurons. We assessed whether estradiol and feeding conditions modulate a possible interaction between leptin and NO in brain areas related to the control of reproductive function. Estradiol-treated and untreated ovariectomized rats were normally fed or fasted for 48 h. Then, saline (control) or leptin (3 μg/1 μl) intracerebroventricular microinjections were administered, and after thirty minutes, the brains collected subsequent to the decapitation or transcardially perfusion. Leptin and estradiol increased NO synthase (nNOS) gene expression (RT-PCR) and content (Western blotting) in the medial preoptic area (MPOA) and medial basal hypothalamus (MBH) only in fasted rats. Leptin increased: 1-phosphorylated-signal transducer and activator of transcription-3(pSTAT3) (immunohistochemistry) in the MPOA and various hypothalamic nuclei [arcuate (ARC); ventromedial (VMH); dorsal/ventral dorsomedial (dDMH/vDMH); premammilar ventral (PMV)], effects potentiated by estradiol/fasting interaction; 2- nNOS/pSTAT3 coexpression in the MPOA only in estradiol-treated, fasted rats; 3- nNOS-immunoreactive cell expression in the VMH, DMH and PMV (areas related to reproductive function control) of estradiol -treated rats. Thus, when leptin is reduced during fasting, leptin replacement effectively increased the expression of nitric oxide, which activated the HPG axis only in the presence of estradiol. Estradiol modulates the nitrergic system, leptin sensitivity and consequently leptin's effects on the nitrergic system in hypothalamus and in particular vDMH and PMV.

COVID-19 Catatonia—Would We Even Know?

COVID-19 Catatonia—Would We Even Know?

0156 Activation of Glutamatergic PPT Neurons and Their Projections Promotes Arousal, and Distinct Wake Behaviors

Abstract Introduction The pedunculopontine tegmental (PPT) region in the brainstem is crucial for the regulation of sleep/wake states. We recently showed that chemogenetic activation of glutamatergic PPT neurons promotes wakefulness for several hours. Here we used optogenetic activation of these neurons to further investigate the mechanisms and pathways through which PPT glutamatergic neurons produce wakefulness. Methods Using vGlut2-cre mice, we transfected neurons in the PPT region with a viral vector coding for cre-dependent ChR2 tagged with fluorescent mCherry and implanted bilateral optical fibers above the PPT nuclei as well as EEG/EMG leads. Two weeks later, we administered blue laser light to activate ChR2-expressing neurons and recorded sleep/wake states. Results Activation of ChR2-expressing glutamatergic neurons during NREM sleep rapidly elicited wakefulness in a stimulation-frequency dependent manner, with higher frequencies producing wake more quickly and with longer duration. Random, automated stimulation for 10 s at 5 Hz over 24 h revealed that activation of glutamatergic PPT neurons produces rapid arousals form NREM sleep. Importantly, stimulation did not wake mice from REM sleep, suggesting that glutamatergic PPT signaling does not interfere with REM sleep. To map the target areas through which PPT glut neurons produce wakefulness, we used a viral tracer to visualize PPT glutamatergic projections, and then optogenetically stimulated terminals in 1) basal forebrain, 2) lateral hypothalamus, 3) thalamus, and 4) substantia nigra. We found that stimulating terminals in all of these regions woke mice from NREM sleep, and stimulating terminals in the basal forebrain and lateral hypothalamus produced a number of active wake behaviors such as locomotion. In contrast, stimulation of PPT glut soma and terminals in the thalamus and substantia nigra results mainly in quiet wakefulness. Conclusion Glutamatergic PPT neurons potently promote arousal from NREM sleep but not REM sleep, and the resulting wake behavior is modulated by different projection targets. Support NIH grant P01 - HL095491

MKRN3 inhibits the reproductive axis through actions in kisspeptin-expressing neurons.

The identification of loss-of-function mutations in MKRN3 in patients with central precocious puberty in association with the decrease in MKRN3 expression in the medial basal hypothalamus of mice before the initiation of reproductive maturation suggests that MKRN3 is acting as a brake on gonadotropin-releasing hormone (GnRH) secretion during childhood. In the current study, we investigated the mechanism by which MKRN3 prevents premature manifestation of the pubertal process. We showed that, as in mice, MKRN3 expression is high in the hypothalamus of rats and nonhuman primates early in life, decreases as puberty approaches, and is independent of sex steroid hormones. We demonstrated that Mkrn3 is expressed in Kiss1 neurons of the mouse hypothalamic arcuate nucleus and that MKRN3 repressed promoter activity of human KISS1 and TAC3, 2 key stimulators of GnRH secretion. We further showed that MKRN3 has ubiquitinase activity, that this activity is reduced by MKRN3 mutations affecting the RING finger domain, and that these mutations compromised the ability of MKRN3 to repress KISS1 and TAC3 promoter activity. These results indicate that MKRN3 acts to prevent puberty initiation, at least in part, by repressing KISS1 and TAC3 transcription and that this action may involve an MKRN3-directed ubiquitination-mediated mechanism.

Deep brain stimulation of hypothalamus for narcolepsy-cataplexy in mice

BackgroundNarcolepsy type 1 (NT1, narcolepsy with cataplexy) is a disabling neurological disorder caused by loss of excitatory orexin neurons from the hypothalamus and is characterized by decreased motivation, sleep-wake fragmentation, intrusion of rapid-eye-movement sleep (REMS) during wake, and abrupt loss of muscle tone, called cataplexy, in response to sudden emotions. ObjectiveWe investigated whether subcortical stimulation, analogous to clinical deep brain stimulation (DBS), would ameliorate NT1 using a validated transgenic mouse model with postnatal orexin neuron degeneration. MethodsUsing implanted electrodes in freely behaving mice, the immediate and prolonged effects of DBS were determined upon behavior using continuous video-electroencephalogram-electromyogram (video/EEG/EMG) and locomotor activity, and neural activation in brain sections, using immunohistochemical labeling of the immediate early gene product c-Fos. ResultsBrief 10-s stimulation to the region of the lateral hypothalamus and zona incerta (LH/ZI) dose-responsively reversed established sleep and cataplexy episodes without negative sequelae. Continuous 3-h stimulation increased ambulation, improved sleep-wake consolidation, and ameliorated cataplexy. Brain c-Fos from mice sacrificed after 90 min of DBS revealed dose-responsive neural activation within wake-active nuclei of the basal forebrain, hypothalamus, thalamus, and ventral midbrain. ConclusionAcute and continuous LH/ZI DBS enhanced behavioral state control in a mouse model of NT1, supporting the feasibility of clinical DBS for NT1 and other sleep-wake disorders.

Nutritionally induced tanycytic plasticity in the hypothalamus of adult ewes

The blood–brain barrier regulates the transport of molecules that convey global energetic status to the feeding circuitry within the hypothalamus. Capillaries within the median eminence (ME) and tight junctions between tanycytes lining the third ventricle (3V) are critical components of this barrier. Herein, we tested the hypothesis that altering the plane of nutrition results in the structural reorganization of tanycytes, tight junctions, and capillary structure within the medial basal hypothalamus. Proopiomelanocortin (POMC) neuronal content within the arcuate nucleus of the hypothalamus (ARC) was also assessed to test whether reduced nutritional status improved access of nutrients to the ARC, while decreasing the access of nutrients of overfed animals. Multiparous, nongestating ewes were stratified by weight and randomly assigned to dietary treatments offered for 75 d: 200% of dietary recommendations (overfed), 100% of dietary recommendations (control), or 60% of dietary recommendations (underfed). The number of POMC-expressing neurons within the ARC was increased (P ≤ 0.002) in underfed ewes. Overfeeding increased (P ≤ 0.01) tanycyte cellular process penetration and density compared with control and underfeeding as assessed using vimentin immunostaining. Immunostaining of tight junctions along the wall of the 3V did not differ (P = 0.32) between treatments. No differences were observed in capillary density (P = 0.21) or classification (P ≥ 0.47) within the ME. These results implicate that changes within the satiety center and morphology of tanycytes within the ARC occur as an adaptation to nutrient availability.

Imaging the Premonitory Phase of Migraine.

Migraine is a common and disabling brain disorder with a broad and heterogeneous phenotype, involving both pain and painless symptoms. Over recent years, more clinical and research attention has been focused toward the premonitory phase of the migraine attack, which can start up to days before the onset of head pain. This early phase can involve symptomatology, such as cognitive and mood change, yawning, thirst and urinary frequency and sensory sensitivities, such as photophobia and phonophobia. In some patients, these symptoms can warn of an impending headache and therefore offer novel neurobiological insights and therapeutic potential. As well as characterization of the phenotype of this phase, recent studies have attempted to image this early phase using functional neuroimaging and tried to understand how the symptoms are mediated, how a migraine attack may be initiated, and how nociception may follow thereafter. This review will summarize the recent and evolving findings in this field and hypothesize a mechanism of subcortical and diencephalic brain activation during the start of the attack, including that of basal ganglia, hypothalamus, and thalamus prior to headache, which causes a top-down effect on brainstem structures involved in trigeminovascular nociception, leading ultimately to headache.

The quail genome: insights into social behaviour, seasonal biology and infectious disease response

BackgroundThe Japanese quail (Coturnix japonica) is a popular domestic poultry species and an increasingly significant model species in avian developmental, behavioural and disease research.ResultsWe have produced a high-quality quail genome sequence, spanning 0.93 Gb assigned to 33 chromosomes. In terms of contiguity, assembly statistics, gene content and chromosomal organisation, the quail genome shows high similarity to the chicken genome. We demonstrate the utility of this genome through three diverse applications. First, we identify selection signatures and candidate genes associated with social behaviour in the quail genome, an important agricultural and domestication trait. Second, we investigate the effects and interaction of photoperiod and temperature on the transcriptome of the quail medial basal hypothalamus, revealing key mechanisms of photoperiodism. Finally, we investigate the response of quail to H5N1 influenza infection. In quail lung, many critical immune genes and pathways were downregulated after H5N1 infection, and this may be key to the susceptibility of quail to H5N1.ConclusionsWe have produced a high-quality genome of the quail which will facilitate further studies into diverse research questions using the quail as a model avian species.

Conserved Genoarchitecture of the Basal Hypothalamus in Zebrafish Embryos.

Analyses of genoarchitecture recently stimulated substantial revisions of anatomical models for the developing hypothalamus in mammalian and other vertebrate systems. The prosomeric model proposes the hypothalamus to be derived from the secondary prosencephalon, and to consist of alar and basal regions. The basal hypothalamus can further be subdivided into tuberal and mamillary regions, each with distinct subregions. Albeit being a widely used model system for neurodevelopmental studies, no detailed genoarchitectural maps exist for the zebrafish (Danio rerio) hypothalamus. Here, we compare expression domains of zebrafish genes, including arxa, shha, otpa, isl1, lhx5, nkx2.1, nkx2.2a, pax6, and dlx5a, the orthologs of which delimit specific subregions within the murine basal hypothalamus. We develop the highly conserved brain-specific homeobox (bsx) gene as a novel marker for genoarchitectural analysis of hypothalamic regions. Our comparison of gene expression patterns reveals that the genoarchitecture of the basal hypothalamus in zebrafish embryos 48 hours post fertilization is highly similar to mouse embryos at E13.5. We found the tuberal hypothalamus in zebrafish embryos to be relatively large and to comprise previously ill-defined regions around the posterior hypothalamic recess. The mamillary hypothalamus is smaller and concentrates to rather medial areas in proximity to the anterior end of the neural tube floor plate. Within the basal hypothalamus we identified longitudinal and transverse tuberal and mamillary subregions topologically equivalent to those previously described in other vertebrates. However, the hypothalamic diencephalic boundary region and the posterior tuberculum still provide a challenge. We applied the updated prosomeric model to the developing zebrafish hypothalamus to facilitate cross-species comparisons. Accordingly, we applied the mammalian nomenclature of hypothalamic organization to zebrafish and propose it to replace some controversial previous nomenclature.

Regulation of prepubertal dynorphin secretion in the medial basal hypothalamus of the female rat.

The onset of puberty is the result of an increase in secretion of hypothalamic gonadotrophin‐releasing hormone (GnRH). This action is a result of not only the development of stimulatory inputs to its release, but also the gradual decrease in inhibitory inputs that restrain release of the peptide prior to pubertal onset. Dynorphin (DYN) is one of the inhibitory inputs produced in the medial basal hypothalamus (MBH); however, little is known about what substance(s) control its prepubertal synthesis and release. Because neurokinin B (NKB) increases in the hypothalamus as puberty approaches, we considered it a candidate for such a role. An initial study investigated the acute effects of an NKB agonist, senktide, on the secretion of DYN from MBH tissues incubated in vitro. In other experiments, central injections of senktide were administered to animals for 4 days then MBHs were collected for assessment of DYN synthesis or for the in vitro secretion of both DYN and GnRH. Because insulin‐like growth factor (IGF)‐1 has been shown to play an important role at puberty, additional animals received central injections of this peptide for 4 days to assess NKB and DYN synthesis or the in vitro secretion of NKB. The results obtained show that senktide administration up‐regulates the NKB receptor protein, at the same time as suppressing the DYN and its receptor. Senktide consistently suppressed DYN and elevated GnRH secretion in the same tissue incubates from both the acute and chronic studies. IGF‐1 administration caused an increase in NKB protein, at the same time as decreasing DYN protein. Furthermore, the central administration of IGF‐1 caused an increase in NKB release, an action blocked by the IGF‐1 receptor blocker, JB‐1. These results indicate that the IGF‐1/NKB pathway contributes to suppressing the DYN inhibitory tone on prepubertal GnRH secretion and thus facilitates the puberty‐related increase in the release of GnRH to accelerate the onset of puberty.

Glucose Increase DAGLα Levels in Tanycytes and Its Inhibition Alters Orexigenic and Anorexigenic Neuropeptides Expression in Response to Glucose

The endocannabinoid system (ECS) is composed of a group of Gi-coupled protein receptors and enzymes, producing and degrading the endocannabinoids, 2-arachidonoylglycerol (2-AG) and N-arachidonoyl-ethanolamine (AEA). Endocannabinoid-mediated signaling modulates brain functions, such as pain, mood, memory, and feeding behavior. The activation of the ECS is associated with overeating and obesity; however, the expression of components of this system has been only partially studied in the hypothalamus, a critical region implicated in feeding behavior. Within this brain region, anorexigenic, and orexigenic neurons of the arcuate nucleus (ARC) are in close contact with tanycytes, glial radial-like cells that line the lateral walls and floor of the third ventricle (3V). The specific function of tanycytes and the effects of metabolic signals generated by them on adjacent neurons is starting to be elucidated. We have proposed that the ECS within tanycytes modulates ARC neurons, thus modifying food intake. Here, we evaluated the expression and the loss of function of the 2-AG-producing enzyme, diacylglycerol lipase-alpha (DAGLα). Using Western blot and immunohistochemistry analyses in basal hypothalamus sections of adult rats under several glycemic conditions, we confirm that DAGLα is strongly expressed at the basal hypothalamus in glial and neuronal cells, increasing further in response to greater extracellular glucose levels. Using a DAGLα-inhibiting adenovirus (shRNA), suppression of DAGLα expression in tanycytes altered the usual response to intracerebroventricular glucose in terms of neuropeptides produced by neurons of the ARC. Thus, these results strongly suggest that the tanycytes could generate 2-AG, which modulates the function of anorexigenic and orexigenic neurons.

Multiple failures in the lutenising hormone surge generating system in GABAB1KO female mice.

Female mice lacking GABAB receptors, GABAB1KO, show disrupted oestrous cycles, reduced pregnancies and increased hypothalamic Gnrh1 mRNA expression, whereas anteroventral periventricular/periventricular preoptic nucleus (AVPV/PeN) Kiss1 mRNA was not affected. In the present study, we characterise the important components of the gonadotrophic preovulatory surge, aiming to unravel the origin of this reproductive impairment. In GABAB1KO and wild-type (WT) females, we determined: (i) hypothalamic oestrogen receptor (ER)α and β and aromatase mRNA and protein expression; (ii) ovulation index and oestrus serum follicle-stimulating hormone (FSH) and pituitary Gnrh1r expression; (iii) in ovariectomised-oestradiol valerate-treated mice, we evaluated ex vivo hypothalamic gonadotrophin-releasing hormone (GnRH) pulsatility in the presence/absence of kisspeptin (Kiss-10, constant or pulsatile) and oestradiol (constant); and (iv) in ovariectomised-oestradiol silastic capsule-treated mice (proestrous-like environment), we evaluated morning and evening kisspeptin neurone activation (c-Fos+) and serum luteinising homrone (LH). In the medial basal hypothalamus of oestrus GABAB1KOs, aromatase and ERα mRNA and protein were increased, whereas ERβ was decreased. In GABAB1KOs, the ovulation index was decreased together with decreased first oestrus serum FSH and increased pituitary Gnrh1r mRNA. Under constant Kiss-10 stimulation, hypothalamic GnRH pulse frequency did not vary, although GnRH mass/pulse was increased in GABAB1KOs. In WTs, pulsatile Kiss-10 together with constant oestradiol significantly increased GnRH pulsatility, whereas, in GABAB1KOs, oestradiol alone increased GnRH pulsatility and this was reversed by pulsatile Kiss-10 addition. In GABAB1KOs AVPV/PeN kisspeptin neurones were similarly activated (c-Fos+) in the morning and evening, whereas WTs showed the expected, marked evening stimulation. LH correlated with activated kisspeptin cells in WT mice, whereas GABAB1KO mice showed high, similar LH levels both in the morning and evening. Taken together, all of these alterations point to impairment in the trigger of the preovulatory GnRH surge that entails the reproductive alterations described.