Preoptic Nucleus Research Articles

Providing or receiving alloparental care promote partner preference and alter central oxytocin and dopamine systems in adult mandarin voles

Juveniles of cooperative breeding species usually remain in the natal area and provide care to younger siblings, a behavior considered one form of alloparenting in the natural condition. Previous studies have demonstrated the effects of providing or receiving alloparental care on adult behaviors, including anxiety-like behavior, social interaction, and parental behavior, but little is known about the influences on species-typical bonding behaviors, such as pair-bond formation. In this study, we explored this concept using socially monogamous mandarin voles (Lasiopodomys mandarinus). As the oxytocin (OT) and dopamine systems are involved in alloparental and pair-bonding behaviors, we also examined the levels of central OT and tyrosine hydroxylase (TH), as well as OT receptor (OTR) and dopamine D1-type and D2-type receptors (D1R and D2R) mRNA expression in the nucleus accumbens (NAcc) and amygdala to investigate the underlying mechanisms. Our results show that mandarin voles providing alloparental care to younger siblings displayed facilitation of partner preference formation, lower levels of OT expression in the paraventricular nucleus of the hypothalamus (PVN) and lateral hypothalamus (LH), and increased OTR and D2R mRNA expression in the NAcc compared to controls. Individuals receiving alloparental care also demonstrated facilitation of partner preference formation in adult voles. Additionally, alloparental care enhanced OT expression in the PVN, anterior medial preoptic nucleus (MPOAa), medial amygdala (MeA), and TH expression in the ventral tegmental area (VTA) and zona incerta (ZI). Furthermore, males displayed decreased D1R mRNA expression in the NAcc, whereas females showed slightly increased D2R expression in the amygdala. These results demonstrate that providing or received alloparental care can promote partner preference formation in monogamous species and that these changes are associated with altered OT and dopamine levels and their receptors in specific brain regions.

Ontogenetic variations of proteins in neurons of the lateral preoptic nucleus of rats' hypothalamus under a modified light regime.

Proteins can be key biochemical markers for evaluating the functional activity of nervous system cells. They are involved in the proliferation and differentiation of nerve and glial cells and the arrangement of many metabolic functions of the brain. This study aimed to analyze the concentration of proteins in the neurons of the lateral preoptic nucleus (LPON) of the hypothalamus in mature and old rats under standard and altered lighting conditions. Our results show that the concentration of proteins in mature rats was significantly higher than in old rats (0.274±0.0017 optical density units), with a predominance of carboxyl groups, indicating a high intensity of protein metabolism. Additionally, we found that changes in the lighting regime have a differential effect on the optical density of specific staining for protein in LPON neurons. Specifically, light deprivation did not significantly alter the optical density of specific staining for protein in neurons of the hypothalamus LPON of mature rats regardless of the period of the day, while in old rats, the intensity of protein staining decreased. Light exposure, on the other hand, led to an increase in the average color intensity for protein in neurons of the hypothalamus LPON in mature rats (0.326±0.0014 optical density units), while in old rats, a decrease in the average color intensity for protein in neurons of the hypothalamus LPON was observed (0.196±0.0017 optical density units).

A progestin regulates the prostaglandin pathway in the neuroendocrine system in female mudskipper Boleophthalmus pectinirostris

Sex hormones regulate the reproductive cycle through brain-pituitary axis, but the molecular mechanism is still enigmatic. In the reproductive season, the mudskipper Boleophthalmus pectinirostris possesses a semilunar periodicity spawning rhythm, which coincides with the semilunar periodicity variations in 17α-hydroxyprogesterone, the precursor of 17α,20β-dihydroxy-4-pregnen-3-one (DHP), a sexual progestin in teleosts. In the present study, we investigated in vitro the brain transcriptional differences between DHP-treated tissues and control groups using RNA-seq. Differential expression analysis revealed that 2700 genes significantly differentially expressed, including 1532 up-regulated and 1168 down-regulated genes. The majority of prostaglandin pathway-related genes were dramatically up-regulated, especially the prostaglandin receptor 6 (ptger6). Tissue distribution analysis revealed that ptger6 gene was ubiquitously expressed. In situ hybridization results showed that ptger6, nuclear progestin receptor (pgr), and DHP-induced c-fos mRNA were co-expressed in the ventral telencephalic area, the ventral nucleus of ventral telencephalic area, the anterior part of parvocellular preoptic nucleus, the magnocellular part of magnocellular preoptic nucleus, the ventral zone of periventricular hypothalamus, the anterior tubercular nucleus, the periventricular nucleus of posterior tuberculum, and the torus longitudinalis. DHP significantly enhanced promoter activities of ptger6 via Pgr. Together, this study suggested that DHP regulates the prostaglandin pathway in the neuroendocrine system of teleost fish.

Cellular Localization of Orexin 1 Receptor in Human Hypothalamus and Morphological Analysis of Neurons Expressing the Receptor.

The orexin system is related to food behavior, energy balance, wakefulness and the reward system. It consists of the neuropeptides orexin A and B, and their receptors, orexin 1 receptor (OX1R) and orexin 2 receptor (OX2R). OX1R has selective affinity for orexin A, and is implicated in multiple functions, such as reward, emotions, and autonomic regulation. This study provides information about the OX1R distribution in human hypothalamus. The human hypothalamus, despite its small size, demonstrates a remarkable complexity in terms of cell populations and cellular morphology. Numerous studies have focused on various neurotransmitters and neuropeptides in the hypothalamus, both in animals and humans, however, there is limited experimental data on the morphological characteristics of neurons. The immunohistochemical analysis of the human hypothalamus revealed that OX1R is mainly found in the lateral hypothalamic area, the lateral preoptic nucleus, the supraoptic nucleus, the dorsomedial nucleus, the ventromedial nucleus, and the paraventricular nucleus. The rest of the hypothalamic nuclei do not express the receptor, except for a very low number of neurons in the mammillary bodies. After identifying the nuclei and neuronal groups that were immunopositive for OX1R, a morphological and morphometric analysis of those neurons was conducted using the Golgi method. The analysis revealed that the neurons in the lateral hypothalamic area were uniform in terms of their morphological characteristics, often forming small groups of three to four neurons. A high proportion of neurons in this area (over 80%) expressed the OX1R, with particularly high expression in the lateral tuberal nucleus (over 95% of neurons). These results were analyzed, and shown to represent, at the cellular level, the distribution of OX1R, and we discuss the regulatory role of orexin A in the intra-hypothalamic areas, such as its special role in the plasticity of neurons, as well as in neuronal networks of the human hypothalamus.

Activation of the nociceptin/orphanin-FQ receptor promotes NREM sleep and EEG slow wave activity

Sleep/wake control involves several neurotransmitter and neuromodulatory systems yet the coordination of the behavioral and physiological processes underlying sleep is incompletely understood. Previous studies have suggested that activation of the Nociceptin/orphanin FQ (N/OFQ) receptor (NOPR) reduces locomotor activity and produces a sedation-like effect in rodents. In the present study, we systematically evaluated the efficacy of two NOPR agonists, Ro64-6198 and SR16835, on sleep/wake in rats, mice, and Cynomolgus macaques. We found a profound, dose-related increase in non-Rapid Eye Movement (NREM) sleep and electroencephalogram (EEG) slow wave activity (SWA) and suppression of Rapid Eye Movement sleep (REM) sleep in all three species. At the highest dose tested in rats, the increase in NREM sleep and EEG SWA was accompanied by a prolonged inhibition of REM sleep, hypothermia, and reduced locomotor activity. However, even at the highest dose tested, rats were immediately arousable upon sensory stimulation, suggesting sleep rather than an anesthetic state. NOPR agonism also resulted in increased expression of c-Fos in the anterodorsal preoptic and parastrial nuclei, two GABAergic nuclei that are highly interconnected with brain regions involved in physiological regulation. These results suggest that the N/OFQ-NOPR system may have a previously unrecognized role in sleep/wake control and potential promise as a therapeutic target for the treatment of insomnia.

The hyperthermic response to intra-preoptic area administration of agmatine in male rats

Agmatine is an endogenous biogenic amine that exerts various effects on the central nervous system. The hypothalamic preoptic area (POA, thermoregulatory command center) has high agmatine immunoreactivity. In this study, in conscious and anesthetized male rats, agmatine microinjection into the POA induced hyperthermic responses associated with increased heat production and locomotor activity. Intra-POA administration of agmatine increased the locomotor activity, the brown adipose tissue temperature and rectum temperature, and induced shivering as demonstrated by increased neck muscle electromyographic activity. However, intra-POA administration of agmatine almost had no impact on the tail temperature of anesthetized rats. Furthermore, there were regional differences in the response to agmatine in the POA. The most effective sites for the microinjection of agmatine to elicit hyperthermic responses were localized in the medial preoptic area (MPA). Agmatine microinjection into the median preoptic nucleus (MnPO) and lateral preoptic nucleus (LPO) had a minimal effect on the mean core temperature. Analysis of the in vitro discharge activity of POA neurons in brain slices when perfused with agmatine showed that agmatine inhibited most warm-sensitive but not temperature-insensitive neurons in the MPA. However, regardless of thermosensitivity, the majority of MnPO and LPO neurons were not responsive to agmatine. The results demonstrated that agmatine injection into the POA of male rats, especially the MPA, induced hyperthermic responses, which may be associated with increased BAT thermogenesis, shivering and locomotor activity by inhibiting warm-sensitive neurons.

The effects of delta-9-tetrahydrocannabinol administration in the regulation of female rat sociosexual behaviour.

By targeting the endocannabinoid system, delta-9-tetrahydrocannabinol (THC) modulates female motivated behaviours, influenced by sex hormones. Both medial preoptic nucleus (MPN) and ventromedial nucleus of the hypothalamus (VMN) are involved in the modulation of female sexual responses. The first triggers proceptivity, whereas the ventrolateral division of the latter (VMNvl) triggers receptivity. These nuclei are modulated by glutamate, which inhibits female receptivity, and GABA, which has a dichotomous action in female sexual motivation. Here, we evaluated the action of THC on the modulation of social and sexual behaviours, on signalling pathways of MPN and VMNvl and how sex hormones influence these parameters. Young ovariectomized female rats, given sex hormones (oestradiol benzoate, EB, and progesterone, P) and THC were used for behavioural testing and for immunofluorescence analyses of vesicular glutamate transporter 2 (VGlut2) and GAD (glutamic acid decarboxylase)67 expression. Results showed that females given EB + P exhibited a higher preference for male partner, as well as higher proceptivity and a higher receptivity than control or females given only EB. Females treated with THC presented similar responses in control or EB + P female rats and even more facilitated behavioural responses in EB females than the ones that did not receive THC. Immunofluorescence results in the MPN exhibited a decreased expression of GAD67 and VGlut2 in EB + THC-treated female rats. Within VMNvl of EB-primed rats no changes in the expression of both proteins were observed after THC exposure. This study demonstrates how the possible outcomes of endocannabinoid system instability within hypothalamic neuron connectivity can modify female rat sociosexual behaviour.

Prostaglandin D2 Controls Local Blood Flow and Sleep-Promoting Neurons in the VLPO via Astrocyte-Derived Adenosine.

Prostaglandin D2 (PGD2) is one of the most potent endogenous sleep-promoting molecules. However, the cellular and molecular mechanisms of the PGD2-induced activation of sleep-promoting neurons in the ventrolateral preoptic nucleus (VLPO), the major nonrapid eye movement (NREM)-sleep center, still remains unclear. We here show that PGD2 receptors (DP1) are not only expressed in the leptomeninges but also in astrocytes from the VLPO. We further demonstrate, by performing real-time measurements of extracellular adenosine using purine enzymatic biosensors in the VLPO, that PGD2 application causes a 40% increase in adenosine level, via an astroglial release. Measurements of vasodilatory responses and electrophysiological recordings finally reveal that, in response to PGD2 application, adenosine release induces an A2AR-mediated dilatation of blood vessels and activation of VLPO sleep-promoting neurons. Altogether, our results unravel the PGD2 signaling pathway in the VLPO, controlling local blood flow and sleep-promoting neurons, via astrocyte-derived adenosine.

Plastic rearrangement of basal forebrain parvalbumin-immunoreactive neurons in the kainite model of epilepsy.

Temporal lobe epilepsy (TLE) is the most prevalent form of epilepsy, through the neuronal mechanisms of this syndrome remain elusive. In addition to the temporal lobe structures, it was found that the basal forebrain cholinergic cells are also involved in epileptogenesis. However, little is known about the involvement of the basal forebrain GABAergic neurons in epilepsy; despite this, they largely project to the temporal lobe and are crucial for the regulation of the hippocampal circuitry. In this study, we assessed epilepsy-induced changes in parvalbumin (PARV) immunoreactive neurons of the medial septum (MS) and of the magnocellular preoptic nucleus (MCPO) using the kainic acid (KA) model in rats. In addition, we estimated the respective changes in the cholinergic varicosities in the MS, where we observed a significant reduction in the PARV cell number (12849 ± 2715 vs. 9372 ± 1336, p = .029) and density (16.2 ± 2.62 vs. 10.5 ± 1.00 per .001 mm3, p =.001), and an increase in the density of cholinergic varicosities (47.9 ± 11.1 vs. 69.4 ± 17.8 per 30,000 µm2, p =.036) in KA-treated animals. In the MCPO, these animals showed a significant increase in somatic volume (827.9 ± 235.2 µm3 vs. 469.9 ± 79.6 µm3, p = .012) and total cell number (2268.6 ± 707.1 vs. 1362.4 ± 262.0, p =.028). These results show that the basal forebrain GABAergic cell populations undergo numerical and morphological changes in epileptic animals, which may contribute to an increased vulnerability of brain circuits to epilepsy and epilepsy-related functional impairments.

Male minipuberty involves the gonad-independent activation of preoptic nNOS neurons.

The maturation of the hypothalamic-pituitary-gonadal (HPG) axis is crucial for the establishment of reproductive function. In female mice, neuronal nitric oxide synthase (nNOS) activity appears to be key for the first postnatal activation of the neural network promoting the release of gonadotropin-releasing hormone (GnRH), i.e. minipuberty. However, in males, the profile of minipuberty as well as the role of nNOS-expressing neurons remain unexplored. nNOS-deficient and wild-type mice were studied during postnatal development. The expression of androgen (AR) and estrogen receptor alpha (ERα) as well as nNOS phosphorylation were evaluated by immunohistochemistry in nNOS neurons in the median preoptic nucleus (MePO), where most GnRH neuronal cell bodies reside, and the hormonal profile of nNOS-deficient male mice was assessed using previously established radioimmunoassay and ELISA methods. Gonadectomy and pharmacological manipulation of ERα were used to elucidate the mechanism of minipubertal nNOS activation and the maturation of the HPG axis. In male mice, minipubertal FSH release occurred at P23, preceding the LH surge at P30, when balanopreputial separation occurs. Progesterone and testosterone remained low during minipuberty, increasing around puberty, whereas estrogen levels were high throughout postnatal development. nNOS neurons showed a sharp increase in Ser1412 phosphorylation of nNOS at P23, a phenomenon that occurred even in the absence of the gonads. In male mice, nNOS neurons did not appear to express AR, but abundantly expressed ERα throughout postnatal development. Selective pharmacological blockade of ERα during the infantile period blunted Ser1412 phosphorylation of nNOS at P23. Our results show that the timing of minipuberty differs in male mice when compared to females, but as in the latter, nNOS activity in the preoptic region plays a role in this process. Additionally, akin to male non-human primates, the profile of minipuberty in male mice is shaped by sex-independent mechanisms, and possibly involves extragonadal estrogen sources.

Bulbar projecting subcortical GABAergic neurons send collateral branches extensively and selectively to primary olfactory cortical regions.

Circuit operations of the olfactory bulb are modulated by higher order projections from multiple regions, many of which are themselves targets of bulbar output. Multiple glutamatergic regions project to the olfactory bulb, including the anterior olfactory nucleus (AON), prefrontal cortex (PFC), piriform cortex (PC), entorhinal cortex (EC), and tenia tecta (TT). In contrast, only one region provides GABAergic projections to the bulb. These GABA neurons are located in the horizontal limb of the diagonal band of Broca extending posteriorly through the magnocellular preoptic nucleus to the nucleus of the lateral olfactory bulb. However, it was unclear whether bulbar projecting GABAergic neurons collaterallize projecting to other brain regions. To address this, we mapped collateral projections from bulbar projecting GABAergic neurons using intersectional strategies of viral and traditional tract tracers. This approach revealed bulbar projecting GABAergic neurons show remarkable specificity targeting other primary olfactory cortical regions exhibiting abundant collateral projections into the accessory olfactory bulb, AON, PFC, PC, and TT. The only "nonolfactory" region receiving collateral projections was sparse connectivity to the medial prefrontal orbital cortex. This suggests that basal forebrain inhibitory feedback also modulates glutamatergic feedback areas that are themselves prominent bulbar projection regions. Thus, inhibitory feedback may be simultaneously modulating both synaptic processing of olfactory information in the bulb and associational processing of olfactory information from primary olfactory cortex. We hypothesize that these olfactory GABAergic feedback neurons are a regulator of the entire olfactory system.

Divergent Neural Activity in the VLPO During Anesthesia and Sleep.

The invention of general anesthesia (GA) represents a significant advance in modern clinical practices. However, the exact mechanisms of GA are not entirely understood. Because of the multitude of similarities between GA and sleep, one intriguing hypothesis is that anesthesia may engage the sleep-wake regulation circuits. Here, using fiber photometry and micro-endoscopic imaging of Ca2+ signals at both population and single-cell levels, it investigates how various anesthetics modulate the neural activity in the ventrolateral preoptic nucleus (vLPO), a brain region essential for the initiation of sleep. It is found that different anesthetics primarily induced suppression of neural activity and tended to recruit a similar group of vLPO neurons; however, each anesthetic caused comparable modulations of both wake-active and sleep-active neurons. These results demonstrate that anesthesia creates a different state of neural activity in the vLPO than during natural sleep, suggesting that anesthesia may not engage the same vLPO circuits for sleep generation.

Neurons of the median preoptic nucleus contribute to chronic angiotensin II-salt induced hypertension in the rat.

Experiments were designed to test the hypothesis that median preoptic (MnPO) neurons are necessary for the full hypertensive response to chronic angiotensin II (AngII) in rats consuming a high salt diet. The MnPO is implicated in many of the physiologic actions of AngII, primarily acting as a downstream nucleus to AngII binding at circumventricular organs such as the organum vasculosum of the lamina terminalis (OVLT). We have previously shown a prominent effect of lesion of the OVLT on the chronic hypertensive effects of AngII in rats consuming high salt. Additionally, we have shown that lesion of the MnPO attenuated the hypertensive response to chronic intravenous infusion of AngII in rats. However, whether MnPO neurons or fibers of passage contribute to this response is not clear. Male Sprague Dawley rats were randomly assigned to either sham (SHAM; n=8) or ibotenic acid lesion of the MnPO (MnPOx; n=6). In the MnPOx group, 200 nl of ibotenic acid in phosphate buffer saline (5 μg/μl) was injected into each of 3 predetermined coordinates targeted at the entire MnPO. After a week of recovery, rats were instrumented with radiotelemetric pressure transducers, provided 2.0% NaCl diet and distilled water ad libitum and given another week to recover. After 3 days of baseline measurements, osmotic minipumps were implanted subcutaneously in all rats for administration of AngII at a rate of 150 ng/kg/min. Blood pressure measurements were made for 14 days after minipump implantation. By day 7 of AngII treatment, blood pressure responses appeared to plateau in both groups while the hypertensive response was markedly attenuated in MnPOx rats (MnPOx, 122 ± 6 mmHg; SHAM, 143 ± 8 mmHg). These results support the hypothesis that neurons of the MnPO are involved in the central pathway mediating the chronic hypertensive effects of AngII in rats consuming a high salt diet.

Sedative-hypnotic effects of Boropinol-B on mice via activation of GABAA receptors.

Boropinol-B is a phenylpropanoid compound originally isolated from Boronia pinnata Sm. (Rutaceae). This study aimed to evaluate the sedative-hypnotic effects of Boropinol-B and explore the underlying mechanisms. Pentobarbital sodium-induced sleep mouse model and caffeine-induced insomnia mouse model were used to investigate the sedative effects of Boropinol-B. Pharmacokinetics profiles of Boropinol-B in rats were evaluated by high-performance liquid chromatography. The effects of Boropinol-B on the γ-aminobutyric acid (GABA)ergic system were investigated using ELISA assay and patch-clamp technique. Immunohistochemistry and immunofluorescence were carried out to assess the effects of Boropinol-B on sleep-related brain nucleus. Boropinol-B showed significant sedative effects, including reduced sleep latency, increased sleep duration in pentobarbital sodium-treated mice and decreased locomotor activity in insomnia mice. Pharmacokinetics studies demonstrated that Boropinol-B had a rapid onset of action, a short half-life and no accumulation. It increased the GABA level in mice's brain, and promoted chloride ions influx mediated by the γ-aminobutyric acid type A (GABAA) receptors in neurons. Also, it increased the c-Fos positive ratio of GABAergic neurons in ventrolateral preoptic nucleus and decreased c-Fos expression in tuberomammillary nucleus. Boropinol-B showed significant sedative-hypnotic effects in mice by activating the GABAA receptors and stimulating the sleep-related brain nucleus.

Hypothermia evoked by stimulation of medial preoptic nucleus protects the brain in a mouse model of ischaemia

Therapeutic hypothermia at 32-34 °C during or after cerebral ischaemia is neuroprotective. However, peripheral cold sensor-triggered hypothermia is ineffective and evokes vigorous counteractive shivering thermogenesis and complications that are difficult to tolerate in awake patients. Here, we show in mice that deep brain stimulation (DBS) of warm-sensitive neurones (WSNs) in the medial preoptic nucleus (MPN) produces tolerable hypothermia. In contrast to surface cooling-evoked hypothermia, DBS mice exhibit a torpor-like state without counteractive shivering. Like hypothermia evoked by chemogenetic activation of WSNs, DBS in free-moving mice elicits a rapid lowering of the core body temperature to 32-34 °C, which confers significant brain protection and motor function reservation. Mechanistically, activation of WSNs contributes to DBS-evoked hypothermia. Inhibition of WSNs prevents DBS-evoked hypothermia. Maintaining the core body temperature at normothermia during DBS abolishes DBS-mediated brain protection. Thus, the MPN is a DBS target to evoke tolerable therapeutic hypothermia for stroke treatment.

Human thirst behavior requires transformation of sensory inputs by intrinsic brain networks

BackgroundTo survive and thrive, many animals, including humans, have evolved goal-directed behaviors that can respond to specific physiological needs. An example is thirst, where the physiological need to maintain water balance drives the behavioral basic instinct to drink. Determining the neural basis of such behaviors, including thirst response, can provide insights into the way brain-wide systems transform sensory inputs into behavioral outputs. However, the neural basis underlying this spontaneous behavior remains unclear. Here, we provide a model of the neural basis of human thirst behavior.ResultsWe used fMRI, coupled with functional connectivity analysis and serial-multiple mediation analysis, we found that the physiological need for water is first detected by the median preoptic nucleus (MnPO), which then regulates the intention of drinking via serial large-scale spontaneous thought-related intrinsic network interactions that include the default mode network, salience network, and frontal-parietal control network.ConclusionsOur study demonstrates that the transformation in humans of sensory inputs for a single physiological need, such as to maintain water balance, requires large-scale intrinsic brain networks to transform this input into a spontaneous human behavioral response.

Relative enlargement of the medial preoptic nucleus in the Etruscan shrew, the smallest torpid mammal

Endothermy is a key feature of mammalian biology and enables mammals to maintain stable body temperature and homeostatic functions in the face of a rapidly changing environment. However, when faced with harsh environmental conditions, certain mammalian species enter torpor, a state characterized by reduced metabolism, body temperature, and activity, to minimize energy loss. Etruscan shrews are the smallest mammals, with a surface-to-volume ratio that is very unfavorable for endothermic animals. As a result, Etruscan shrews have an extremely high metabolic rate and are known to enter torpor frequently, presumably as an energy-saving measure. Despite the recent identification of medial preoptic area (MPA) as a key brain region to regulate torpor in mouse, little is known about neural control of torpor in other endothermic animals, including the Etruscan shrew. Here, we confirmed that Etruscan shrews readily enter torpor even in the absence of strong physiological triggers. We then compared the medial preoptic nucleus (MPN) within the MPA of Etruscan shrew and rat, a mammal that does not enter torpor under physiological conditions. While rats have roughly 100 times the body weight and 33 times the brain weight of Etruscan shrews, we find that the male rat MPN exhibits only 6.7 times the volume of that of the male Etruscan shrew. Accordingly, the relative brain volume of the MPN was 6.5-fold larger in shrews, a highly significant difference. Moreover, MPN neuron counts were only roughly twofold lower in shrews than in rats, an astonishing observation considering the interspecies size difference and that neocortical neurons are ~ 20 × more numerous in rats than in shrews. We suggest that the extraordinary enlargement of the Etruscan shrew MPN is a specialization for orchestrating torpor in a mammal with an exceptional metabolism.

LBMON139 A Case of Adipsic Diabetes Insipidus In Patient With Third Ventricular Tumor And Right Frontal Craniotomy.

Abstract Introduction Adipsic diabetes insipidus (ADI) is a rare hypothalamic disorder consisting of central diabetes insipidus (CDI) and loss of thirst. In hyperosmolar state, signals from osmosensors integrate in the central thirst center resulting in stimulatory signals between subfornical-oragan, organum-vasculosm of lamina terminalis and median preoptic nucleus increasing thirst and release of vasopressin. Disruption in this mechanism leads to adipsia. Case presentation 27 yr old male with history of prediabetes, 4.6cm third ventricular epidermoid cyst s/p endoscopic ventriculosmoy, hypogonadotropic hypogonadism, central hypothyroidism, and CDI underwent right frontal craniotomy for residual third ventricular cyst. Developed worsening DI, new onset hyperglycemia, and secondary adrenal insufficiency. Discharged with oral DDAVP 300mcg oral twice daily for CDI. 1 week later presented to ED with weakness. BP 132/112, HR 139, RR 38, SPO2 94%. Labs significant for corrected sodium of 172 (136-145mmol/L), glucose 699 (70-99mg/dl), calcium 11.8 (8.3-10.6 mg/dl). Discharged after 3 weeks with intranasal DDAVP 10mcg twice daily (BID). Again presented 1 week after for weakness. Vitals BP 105/64, HR 134, F 37.3 C, RR 31, SPO2 96%. Corrected sodium of 174 (136-145mmol/L) and glucose 708 (70-99mg/dl). Denied missing medication. Reported no increased water intake. Patient was diagnosed with adipsic DI based on subjective lack of thirst during period of significant hyperosmolar hypernatremia state. Overtime switched to 10mcg BID intranasal DDAVP and started on 4L fixed water intake. Had 5L urine output daily. Sodium levels ranged from 132-137. Discharged on intranasal DDAVP 10mcg AM/20mcg PM, 4L daily fixed water intake, and twice weekly sodium checks as outpatient. Goal sodium 135-140. DDAVP adjusted after sodium rose to 145. At recent clinic visit continued fixed 4L fluid intake with extra 500-1L intake for increased sweating/exercise, and sodium level 134. A1c 10% on insulin, and weight gain of 70lbs since surgery (8mon piror), BMI of 45. Started on GLP-1RA and sleep study. Learning points: Less than 100 cases of ADI reported worldwide and associated with increased morbidity/mortality1. This patient likely developed ADI due to disruption of central thirst center from epidermoid cyst and trans frontal craniotomy. We must be hypervigilant for ADI in patients with third ventricular tumors who undergo frontal craniotomy. Management is complex and requires patients are followed closely with weekly labs, either fixed water intake or fixed DDAVP dose and adjustment depending on labs. Important to screen these patients for obesity and sleep apnea given increased likelihood of hypothalamic dysfunction1. Reference: Cuesta, M., Hannon, M. J. & Thompson, C. J. Adipsic diabetes insipidus in adult patients. Pituitary 20, 372-380 (2017). https://doi.org/10.1007/s11102-016-0784-4 Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

ODP297 Analysis of the responsible region of TRH in the hypothalamus-pituitary-thyroid axis using the Paraventricular nucleus-specific TRH deficient mice.

Abstract Objectives Thyrotropin-releasing hormone (TRH) was the first hypothalamic hormone isolated that stimulates pituitary thyroid-stimulating hormone (TSH) secretion. TRH was later found to be distributed throughout the brain, gastrointestinal tract and pancreaticβ-cells. We previously reported the TRH null mice (conventional TRHKO) which exhibit characteristic tertiary hypothyroidism, however the responsible regionfor the hypothalamic-pituitary-thyroid (HPT) axis remained obscure because of the broad expression of TRH in hypothalamus. Previous studies suggested that TRH in the hypothalamic paraventricular nucleus (PVN) was secreted through the median eminence (ME), however it was not directly demonstrated . To determine the region functionally responsible for the HPT axis, we established and analyzed PVN-specific TRH knock-out (PVN-TRHKO) mice. Methods For the targeting vector, a Neo-loxP cassette was inserted into the 3′-UTR of the Trh gene in ES cells. Another loxP site was placed at intron 1. After we obtained the Trh +/lox [neo+] founder mice, we crossed them with the CAG-FLPe transgenic mice to remove the Neo cassette. The offspring were backcrossed to wild-type mice, producing conditional knock-out mice without the Neo cassette, which were labeled as Trh +/lox . We crossed Trh +/lox with transgenic mice expressing Single-minded homolog (Sim)1-Cre recombinase and created PVN-TRHKO mice (Sim1-Cre; Trh lox/lox mice). We confirmed that most Sim1 was expressed in the PVN using Sim1-Cre/tdTomato mice. We performed the following experiments using PVN-TRHKO andTrh lox/lox mice as control (Ct). 1) immunostaining of TRH using antibody forproTRH in cerebrum, 2)qPCR analysis detecting the expression of preproTrh mRNA in hypothalamic PVN, 3) measurement of the level of serum free-T4 and TSH, 4)qPCR analysis detecting theexpression levels of Tshβ, Prl, Cga, Gh, Pomc and Lhβ gene mRNAin the anterior pituitary and 5)immunohistochemical analysis with antibodies for TSHβ and Prolactin in anterior pituitary. Results In the PVN-TRHKO mice, 1) ProTRH-immunopositive cells were lost in the area of PVN and ME, whereas proTRH detected in the medial preoptic area(MPA) and medial preoptic nucleus (MPO) in the hypothalamus.2)The expression level of proTRHmRNA was decreased to7.7% compared with Ct.3) Free-T4 levels decreased to 50% and the TSH levels increased to 170% of those in Ct. 4) TshβmRNA levels were decreased by 65% and thePrlmRNA levels were reduced to 55% of those in Ct. 5) The number of TSH-positive andProlactin-positive cells in the pituitary significantly decreased to 50% and 60% of those in Ct. Conclusions PVN-TRHKO mice exhibited tertiary hypothyroidism similar to conventional TRHKO. The pathway of TRH neuron from PVN to ME was lost in the PVN-TRHKO mice. These findings are conclusive evidence that the TRH neuron in the PVN is the center of the HPT axis. Presentation: No date and time listed

Spexin in the European sea bass, Dicentrarchus labrax: Characterization, brain distribution, and interaction with Gnrh and Gnih neurons.

Spexin (Spx) is a recently characterized neuropeptide implicated in multiple physiological processes in vertebrates, including reproduction, food intake, and regulation of anxiety and stress. Two orthologs (Spx1 and Spx2) are present in some nonmammalian vertebrates, including teleosts. However, information on the distribution of Spx in the brain and its interactions with other neuroendocrine systems in fish is still scarce. In this work, we cloned and sequenced the sea bass (Dicentrarchus labrax) Spx1, which included a 27 aa signal peptide and a mature peptide of 14 aa that is C-terminal amidated. spx1 transcripts were higher in the diencephalon/caudal preoptic area/hypothalamus and medulla but were also detected in the olfactory bulbs, telencephalon/rostral preoptic area, optic tectum/tegmentum, cerebellum/pons, and pituitary. The immunohistochemical study revealed Spx1-immunoreactive (ir) cells in different nuclei of the preoptic area, habenula, prethalamus, mesencephalic tegmentum and in the proximal pars distalis (PPD) and pars intermedia of the pituitary. Spx1-ir fibers were widely distributed throughout the brain being particularly abundant in the midbrain and hindbrain, in close contact with tegmental gonadotropin-releasing hormone 2 (Gnrh2) cells and isthmic gonadotropin-inhibitory hormone (Gnih) cells of the secondary gustatory nucleus. Moreover, Gnih fibers were observed innervating Spx1-ir cells lying in several subdivisions of the magnocellular preoptic nucleus and in the lateral nucleus of the valvula, whereas ventrolateral prethalamic Spx1-ir cells received immunopositive Gnrh2 fibers. In the pituitary, Gnrh1-ir fibers were observed closely associated with Spx1-ir cells of the PPD. These results suggest that Spx1 could be involved in both reproductive and nonreproductive (i.e., food intake, behavior) functions in sea bass.