Ethanol versus lipopolysaccharide-induced hypothermia: Involvement of urocortin

A Sleep-Specific Midbrain Target for Sevoflurane Anesthesia

Sevoflurane has been the most widely used inhaled anesthetics with a favorable recovery profile; however, the precise mechanisms underlying its anesthetic action are still not completely understood. Here the authors show that sevoflurane activates a cluster of urocortin 1 (UCN1+ )/cocaine- and amphetamine-regulated transcript (CART+ ) neurons in the midbrain involved in its anesthesia. Furthermore, growth hormone secretagogue receptor (GHSR) is highly enriched in sevoflurane-activated UCN1+ /CART+ cells and is necessary for sleep induction. Blockade of GHSR abolishes the excitatory effect of sevoflurane on UCN1+ /CART+ neurons and attenuates its anesthetic effect. Collectively, their data suggest that anesthetic action of sevoflurane necessitates the GHSR activation in midbrain UCN1+ /CART+ neurons, which provides a novel target including the nucleus and receptor in the field of anesthesia.

Oxytocin Receptors in the Mouse Centrally-projecting Edinger-Westphal Nucleus and their Potential Functional Significance for Thermoregulation

The centrally-projecting Edinger-Westphal nucleus (EWcp) has been shown to contribute to regulation of multiple functions, including responses to stress and fear, attention, food consumption, addiction, body temperature and maternal behaviors. However, receptors involved in regulation of these behaviors through EWcp remain poorly characterized. On the other hand, the oxytocin peptide (OXT) is also known to regulate a substantial number of physiological responses and behaviors. Here we show that mRNA encoding OXT receptors (Oxtr) is expressed in EWcp of male and female C57BL/6J mice. These receptors are present on urocortin 1 (Ucn) mRNA-containing neurons and, to a lesser extent, on neurons in EWcp expressing the vesicular glutamate transporter 2 (Vglut2) mRNA of EWcp. Using RNAscope in situ hybridization, we show that neurons containing Ucn and Vglut2 mRNAs are two intermingled, but independent subpopulations in EWcp and characterize their relationship with other populations of neurons in the vicinity of this nucleus. Using immunohistochemistry, we show that intraperitoneal (IP) administration of OXT can induce FOS in Oxtr-containing neurons, suggesting that these receptors on EWcp neurons are functional. A follow up study showed that injection of OXT (2.3 or 7.7 mg/kg, IP) is accompanied by a decrease in body temperature. Since EWcp is known to be involved in regulation of body temperature, we hypothesize that OXT's effects on body temperature could be mediated through the EWcp. The contribution of OXTR in EWcp to regulation of various functions of EWcp and OXT needs to be deciphered.

Vesicular glutamate transporter 2-containing neurons of the centrally-projecting Edinger-Westphal nucleus regulate alcohol drinking and body temperature

Previous studies in rodents have repeatedly demonstrated that the centrally-projecting Edinger-Westphal nucleus (EWcp) is highly sensitive to alcohol and is also involved in regulating alcohol intake and body temperature. Historically, the EWcp has been known as the main site of Urocortin 1 (Ucn1) expression, a corticotropin-releasing factor-related peptide, in the brain. However, the EWcp also contains other populations of neurons, including neurons that express the vesicular glutamate transporter 2 (Vglut2). Here we transduced the EWcp with adeno-associated viruses (AAVs) encoding Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to test the role of the EWcp in alcohol drinking and in the regulation of body temperature. Activation of the EWcp with excitatory DREADDs inhibited alcohol intake in a 2-bottle choice procedure in male C57BL/6J mice, whereas inhibition of the EWcp with DREADDs had no effect. Surprisingly, analysis of DREADD expression indicated Ucn1-containing neurons of the EWcp did not express DREADDs. In contrast, AAVs transduced non-Ucn1-containing EWcp neurons. Subsequent experiments showed that the inhibitory effect of EWcp activation on alcohol intake was also present in male Ucn1 KO mice, suggesting that a Ucn1-devoid population of EWcp regulates alcohol intake. A final set of chemogenetic experiments showed that activation of Vglut2-expressing EWcp neurons inhibited alcohol intake and induced hypothermia in male and female mice. These studies expand on previous literature by indicating that a glutamatergic, Ucn1-devoid subpopulation of the EWcp regulates alcohol consumption and body temperature.

Effects of pharmacological inhibition of the centrally-projecting Edinger-Westphal nucleus on ethanol-induced conditioned place preference and body temperature

Alcohol use disorder is a chronic disease characterized in part by repeated relapsing events. Exposure to environmental stimuli or cues that have previously been associated with the effects of alcohol can promote relapse through the triggering of craving for alcohol. Therefore, identifying and characterizing neuronal populations that may regulate these associations is of the upmost importance. Previous studies have implicated the centrally-projecting Edinger Westphal nucleus (EWcp) in this process, as the EWcp is both sensitive to, and can regulate alcohol intake. To date however, it is unclear if the EWcp is involved in the formation or expression of these alcohol-cue associations. As such, the present studies examined the involvement of the EWcp in male DBA/2J mice in the acquisition and expression of place preference for an alcohol-paired cue using the conditioned place preference (CPP) procedure. Pharmacological inhibition of the EWcp via the GABAA and GABAB receptor agonists muscimol and baclofen did not affect either the acquisition or the expression of CPP. Follow up studies did find however, that pharmacological inhibition of the EWcp increased body temperature and prevented alcohol-induced increases in c-Fos expression in the EWcp. When considered in light of previous studies, the present results indicate that the EWcp may be involved in the regulation of alcohol self-administration, and not conditioned alcohol-seeking. Additionally, the present studies provide further evidence for the involvement of the EWcp in thermoregulation and help elucidate the molecular mechanisms by which alcohol increases c-Fos in the EWcp.

Intrathecal urocortin I in the spinal cord as a murine model of stress hormone-induced musculoskeletal and tactile hyperalgesia

Stress is antinociceptive in some models of pain, but enhances musculoskeletal nociceptive responses in mice and muscle pain in patients with fibromyalgia syndrome. To test the hypothesis that urocortins are stress hormones that are sufficient to enhance tactile and musculoskeletal hyperalgesia, von Frey fibre sensitivity and grip force after injection of corticotropin-releasing factor (CRF), urocortin I and urocortin II were measured in mice. Urocortin I (a CRF1 and CRF2 receptor ligand) produced hyperalgesia in both assays when injected intrathecally (i.t.) but not intracerebroventricularly, and only at a large dose when injected peripherally, suggesting a spinal action. Morphine inhibited urocortin I-induced changes in nociceptive responses in a dose-related fashion, confirming that changes in behaviour reflect hyperalgesia rather than weakness. No tolerance developed to the effect of urocortin I (i.t.) when injected repeatedly, consistent with a potential to enhance pain chronically. Tactile hyperalgesia was inhibited by NBI-35965, a CRF1 receptor antagonist, but not astressin 2B, a CRF2 receptor antagonist. However, while urocortin I-induced decreases in grip force were not observed when co-administered i.t. with either NBI-35965 or astressin 2B, they were even more sensitive to inhibition by astressin, a non-selective CRF receptor antagonist. Together these data indicate that urocortin I acts at CRF receptors in the mouse spinal cord to elicit a reproducible and persistent tactile (von Frey) and musculoskeletal (grip force) hyperalgesia. Urocortin I-induced hyperalgesia may serve as a screen for drugs that alleviate painful conditions that are exacerbated by stress.

Anxiolytic-like effects of antisauvagine-30 in mice are not mediated by CRF2 receptors

The role of brain corticotropin-releasing factor type 2 (CRF₂) receptors in behavioral stress responses remains controversial. Conflicting findings suggest pro-stress, anti-stress or no effects of impeding CRF₂ signaling. Previous studies have used antisauvagine-30 as a selective CRF₂ antagonist. The present study tested the hypotheses that 1) potential anxiolytic-like actions of intracerebroventricular (i.c.v.) administration of antisauvagine-30 also are present in mice lacking CRF₂ receptors and 2) potential anxiolytic-like effects of antisauvagine-30 are not shared by the more selective CRF₂ antagonist astressin₂-B. Cannulated, male CRF₂ receptor knockout (n = 22) and wildtype littermate mice (n = 21) backcrossed onto a C57BL/6J genetic background were tested in the marble burying, elevated plus-maze, and shock-induced freezing tests following pretreatment (i.c.v.) with vehicle, antisauvagine-30 or astressin₂-B. Antisauvagine-30 reduced shock-induced freezing equally in wildtype and CRF₂ knockout mice. In contrast, neither astressin₂-B nor CRF₂ genotype influenced shock-induced freezing. Neither CRF antagonist nor CRF₂ genotype influenced anxiety-like behavior in the plus-maze or marble burying tests. A literature review showed that the typical antisauvagine-30 concentration infused in previous intracranial studies (∼1 mM) was 3 orders greater than its IC₅₀ to block CRF₁-mediated cAMP responses and 4 orders greater than its binding constants (K_d, K_i) for CRF₁ receptors. Thus, increasing, previously used doses of antisauvagine-30 also exert non-CRF₂-mediated effects, perhaps via CRF₁. The results do not support the hypothesis that brain CRF₂ receptors tonically promote anxiogenic-like behavior. Utilization of CRF₂ antagonists, such as astressin₂-B, at doses that are more subtype-selective, can better clarify the significance of brain CRF₂ systems in stress-related behavior.

Forced swim-induced musculoskeletal hyperalgesia is mediated by CRF2 receptors but not by TRPV1 receptors

The exacerbation of musculoskeletal pain by stress in humans is modeled by the musculoskeletal hyperalgesia in rodents following a forced swim. We hypothesized that stress-sensitive corticotropin releasing factor (CRF) receptors and transient receptor vanilloid 1 (TRPV1) receptors are responsible for the swim stress-induced musculoskeletal hyperalgesia. We confirmed that a cold swim (26 °C) caused a transient, morphine-sensitive decrease in grip force responses reflecting musculoskeletal hyperalgesia in mice. Pretreatment with the CRF2 receptor antagonist astressin 2B, but not the CRF1 receptor antagonist NBI-35965, attenuated this hyperalgesia. Desensitizing the TRPV1 receptor centrally or peripherally using desensitizing doses of resiniferatoxin (RTX) failed to prevent the musculoskeletal hyperalgesia produced by cold swim. SB-366791, a TRPV1 antagonist, also failed to influence swim-induced hyperalgesia. Together these data indicate that swim stress-induced musculoskeletal hyperalgesia is mediated, in part, by CRF2 receptors but is independent of the TRPV1 receptor.

Cannabinoid modulation of midbrain urocortin 1 neurones during acute and chronic stress

Neurones in the centrally projecting Edinger-Westphal nucleus (EWcp) are the main site of urocortin 1 (Ucn1) synthesis in the mammalian brain, and are assumed to play a role in the stress response of the animal. Because endocannabinoid signalling has also been strongly implicated in stress, we hypothesised that endocannabinoids may modulate the functioning of the urocortinergic EWcp. First, using in situ hybridisation, we demonstrated cannabinoid receptor 1 (CB1R) mRNA expression in mouse EWcp-neurones that were Ucn1-negative. Dual- and triple-label immunocytochemistry revealed the presence of CB1R in several GABA-immunopositive fibres juxtaposed to EWcp-Ucn1 neurones. To test functional aspects of such an anatomical constellation, we compared acute (1 h of restraint) and chronic (14 days of chronic mild stress) stress-induced changes in wild-type (WT) and CB1R knockout (CB1R-KO) mice. Acute and especially chronic stress resulted in an increase in Ucn1 content of the EWcp, which was attenuated in CB1R-KO mice. CB1R-KO mice had higher basal and chronic stress-induced adrenocorticotrophin and corticosterone levels and were more anxious on the elevated plus-maze versus WT. Collectively, our results show for the first time EWcp-Ucn1 neurones are putatively innervated by endocannabinoid sensitive, inhibitory, GABAergic afferents. In addition, we provide novel evidence that the absence of the CB1 receptor alters the Ucn1 mRNA and peptide levels in EWcp neurones, concomitant with an augmented stress response and increased anxiety-like behaviour.

Sex-specific differences in the dynamics of cocaine- and amphetamine-regulated transcript and nesfatin-1 expressions in the midbrain of depressed suicide victims vs. controls

An intriguing novel pathophysiological insight into mood disorders is the notion that one's metabolic status influences mood. In rodents, cocaine- and amphetamine-regulated transcript (CART) and nesfatin-1/NUCB2 have not only been implicated in metabolism, but in the pathobiology of anxiety and depressive-like behaviour, however they have not previously been investigated in depressed subjects. Both peptides are highly expressed in centrally projecting neurons in the Edinger-Westphal nucleus (EWcp) in the midbrain. The EWcp has been implicated in stress adaptation and stress-related mood disorders like major depressive disorder in a sex-specific manner. This is intriguing, given the fact that females have higher prevalence of mood disorders. Here, we hypothesized that the expression of CART and nesfatin-1 in EWcp would exhibit a sex-specific difference between depressed suicide victims vs. controls. We found that CART and nesfatin/NUCB2 colocalized in the human EWcp, and that CART mRNA content was much higher in both male (×3.8) and female (×5.9) drug-free suicide victims than in controls (persons who died without any diagnosed neurodegenerative or psychiatric disorder). Similarly, NUCB2 mRNA content was also higher (×1.8) in male suicides, whereas in female suicide victims, these contents were ×2.7 lower compared to controls. These observations are the first to show changes in the dynamics of CART and nesfatin/NUCB2 expressions in the midbrain of drug-free depressed suicide victims vs. controls. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Topographical distribution of corticotropin-releasing factor type 2 receptor-like immunoreactivity in the rat dorsal raphe nucleus: co-localization with tryptophan hydroxylase

Corticotropin-releasing factor (CRF) and CRF-related neuropeptides are involved in the regulation of stress-related physiology and behavior. Members of the CRF family of neuropeptides bind to two known receptors, the CRF type 1 (CRF₁) receptor, and the CRF type 2 (CRF₂) receptor. Although the distribution of CRF₂ receptor mRNA expression has been extensively studied, the distribution of CRF₂ receptor protein has not been characterized. An area of the brain known to contain high levels of CRF₂ receptor mRNA expression and CRF₂ receptor binding is the dorsal raphe nucleus (DR). In the present study we investigated in detail the distribution of CRF₂ receptor immunoreactivity throughout the rostrocaudal extent of the DR. CRF₂ receptor-immunoreactive perikarya were observed throughout the DR, with the highest number and density in the mid-rostrocaudal DR. Dual immunofluorescence revealed that CRF₂ receptor immunoreactivity was frequently co-localized with tryptophan hydroxylase, a marker of serotonergic neurons. This study provides evidence that CRF₂ receptor protein is expressed in the DR, and that CRF₂ receptors are expressed in topographically organized subpopulations of cells in the DR, including serotonergic neurons. Furthermore, these data are consistent with the hypothesis that CRF₂ receptors play an important role in the regulation of stress-related physiology and behavior through actions on serotonergic and non-serotonergic neurons within the DR.

Ethanol co-administration moderates 3,4-methylenedioxymethamphetamine effects on human physiology

Alcohol is frequently used in combination with 3,4-methylenedioxymethamphetamine (MDMA). Both drugs affect cardiovascular function, hydration and temperature regulation, but may have partly opposing effects. The present study aims to assess the acute physiologic effects of (co-) administration of MDMA and ethanol over time. A four-way, double blind, randomized, crossover, placebo-controlled study in 16 healthy volunteers (9 male and 7 female) between the ages of 18 and 29. MDMA (100 mg) was given orally and blood ethanol concentration was maintained at pseudo-steady state levels of 0.6 per thousand by a three-hour 10% intravenous ethanol clamp. Cardiovascular function, temperature and hydration measures were recorded throughout the study days. Ethanol did not significantly affect physiologic function, with the exception of a short lasting increase in heart rate. MDMA potently increased heart rate and blood pressure and induced fluid retention as well as an increase in temperature. Co-administration of ethanol with MDMA did not affect cardiovascular function compared to the MDMA alone condition, but attenuated the effects of MDMA on fluid retention and showed a trend for attenuation of MDMA-induced temperature increase. In conclusion, co-administration of ethanol and MDMA did not exacerbate physiologic effects compared to all other drug conditions, and moderated some effects of MDMA alone.

Postnatal developmental profile of urocortin 1 and cocaine- and amphetamine-regulated transcript in the perioculomotor region of C57BL/6J mice

Urocortin 1 (Ucn 1) is an endogenous corticotropin releasing factor (CRF)-related peptide. Ucn 1 is most highly expressed in the perioculomotor urocortin containing neurons (pIIIu), previously known as the non-preganglionic Edinger-Westphal nucleus (npEW). Various studies indicate that these cells are involved in stress adaptation and the regulation of ethanol (EtOH) intake. However, the developmental trajectory of these neurons remained unexamined. Expression of the cocaine- and amphetamine-regulated transcript (CART), which co-localizes with Ucn 1 in the perioculomotor area (pIII) has been examined prenatally, but not postnatally. The goal of the current study was to characterize the ontogenetic profile of Ucn 1 and CART during postnatal development in C57BL/6J (B6) mice. B6 mice were bred, and brains were collected at postnatal days (PND) 1, 4, 8, 12, 16, 24 and 45. Brightfield immunohistochemical staining for Ucn 1 and CART showed that Ucn 1-immunoreactivity (ir) was absent at PND 1, while CART-ir was already apparent in pIIIu at birth, a finding indicating that although the pIIIu neurons have already migrated to their adult position, Ucn 1 expression is triggered in them at later postnatal stages. Ucn 1-ir gradually increased with age, approaching adult levels at PND 16. This developmental profile was confirmed by double-immunofluorescence, which showed that Ucn 1 was absent in CART-positive cells of pIII at PND 4 and that Ucn 1 and CART are strongly but not completely co-localized in pIII at PND 24. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis confirmed that Ucn 1 mRNA levels are significantly lower at PND 4 and PND 12 than in adult animals. The lack of brain Ucn 1 immunoreactivity at birth and the gradual postnatal increase in Ucn 1 in pIIIu suggests that this peptide plays a greater behavioral role in adulthood than during the early postnatal development of an organism.

Comparison of the distributions of urocortin-containing and cholinergic neurons in the perioculomotor midbrain of the cat and macaque

Urocortin is a novel neurotransmitter that appears to play a role in eating and drinking behavior. Most urocortin-positive (urocortin(+)) neurons in rodents are found in the cytoarchitecturally defined Edinger-Westphal nucleus (EW). However, the EW is traditionally described as the source of the preganglionic parasympathetic outflow to the ciliary ganglion. We examined the distribution of urocortin(+) cells and motoneurons by use of immunohistochemical staining for this peptide and for choline acetyltransferase (ChAT) in macaque monkeys, in which most preganglionic motoneurons inhabit the EW, and in cats, in which most do not. In both species, lack of overt double labeling indicated that the ChAT(+) and urocortin(+) cells are separate populations. In the monkey, most nonoculomotor ChAT(+) neurons were found within the EW. In contrast, urocortin(+) cells were distributed mainly between the oculomotor nuclei and in the supraoculomotor area. In the cat, most nonoculomotor ChAT(+) cells were located in the supraoculomotor area and anteromedian nucleus. Few were present in the cat EW. Instead, this nucleus was filled with urocortin(+) cells. These results highlight the fact the term EW has come to indicate different nuclei in different species. Consequently, we have adopted the identifiers preganglionic (EW(PG)) and urocortin-containing (EW(U)) to designate the cytoarchitecturally defined EW nuclei in monkeys and cats, respectively. Furthermore, we propose a new open-ended nomenclature for the perioculomotor (pIII) cells groups that have distinctive projections and neurochemical signatures. This will allow more effective scientific discourse on the connections and function of groups such as the periculomotor urocortin (pIII(U)) and preganglionic (pIII(PG)) populations.

Differences in the urocortin 1 system between long-sleep and short-sleep mice

There is evidence that the peptide urocortin 1 (Ucn1) may be involved in mediating some of the effects of ethanol. The purpose of the present study was to characterize Ucn1 immunoreactivity in mice selectively bred for either high or low sensitivity to ethanol-induced sedation, with additional differences in their response to ethanol-induced hypothermia. The brains of naïve male mice of the inbred long sleep/short sleep (ILS/ISS) selected lines were analyzed by immunohistochemistry. Significant differences were found between lines in the number of Ucn1-containing cells in the non-preganglionic Edinger-Westphal nucleus (npEW, the main source of Ucn1 in the brain); with the ISS mice having more cells. However, significant differences in the optical density of Ucn1 immunoreactivity in individual npEW cells and differences in cell area were also found between lines, with ILS mice having a greater density of Ucn1 per cell and having larger cells in the npEW. Importantly, the ILS mice also had a significantly greater number of Ucn1-positive terminal fibers than ISS mice in the lateral septum and the dorsal raphe nucleus, projection areas of Ucn1-containing neurons. These results suggest that the greater sensitivity of ILS than ISS mice to the hypothermic effects of ethanol could be mediated by stronger innervation of the dorsal raphe by Ucn1-containing fibers. In addition, these results lend further support to previous findings implicating Ucn1-containing projections from npEW to the dorsal raphe in ethanol-induced hypothermia.

Mouse inbred strain differences in ethanol drinking to intoxication

Recently, we described a simple procedure, Drinking in the Dark (DID), in which C57BL/6J mice self-administer ethanol to a blood ethanol concentration (BEC) above 1 mg/ml. The test consists of replacing the water with 20% ethanol in the home cage for 4 h early during the dark phase of the light/dark cycle. Three experiments were conducted to explore this high ethanol drinking model further. In experiment 1, a microanalysis of C57BL/6J behavior showed that the pattern of ethanol drinking was different from routine water intake. In experiment 2, drinking impaired performance of C57BL/6J on the accelerating rotarod and balance beam. In experiment 3, 12 inbred strains were screened to estimate genetic influences on DID and correlations with other traits. Large, reliable differences in intake and BEC were detected among the strains, with C57BL/6J showing the highest values. Strain means were positively correlated with intake and BEC in the standard (24 h) and a limited (4 h) two-bottle ethanol vs. water test, but BECs reached higher levels for DID. Strain mean correlations with other traits in the Mouse Phenome Project database supported previously reported genetic relationships of high ethanol drinking with low chronic ethanol withdrawal severity and low ethanol-conditioned taste aversion. We extend these findings by showing that the correlation estimates remain relatively unchanged even after correcting for phylogenetic relatedness among the strains, thus relaxing the assumption that the strain means are statistically independent. We discuss applications of the model for finding genes that predispose pharmacologically significant drinking in mice.

The urocortin 1 neurocircuit: Ethanol-sensitivity and potential involvement in alcohol consumption

One of the hallmarks of alcoholism is continued excessive consumption of alcohol-containing beverages despite the negative consequences of such behavior. The neurocircuitry regulating alcohol consumption is not well understood. Recent studies have shown that the neuropeptide urocortin 1 (Ucn1), a member of the corticotropin-releasing factor (CRF) family of peptides, could be an important player in the regulation of alcohol consumption. This evidence is accumulated along three directions of research: (1) Ucn 1-containing neurons are extremely sensitive to alcohol; (2) the Ucn1 neurocircuit may contribute to the genetic predisposition to high alcohol intake in mice and rats; (3) manipulation of the Ucn1 system alters alcohol consumption and sensitivity. This paper reviews the current knowledge of the Ucn1 neurocircuit and the evidence for its involvement in alcohol-related behaviors, and proposes a mechanism for its involvement in the regulation of alcohol consumption.

Brain Region-Specific Regulation of Urocortin 1 Innervation and Corticotropin-Releasing Factor Receptor Type 2 Binding by Ethanol Exposure

BACKGROUND

Ethanol administration and consumption selectively activates the urocortin 1 (Ucn1)-expressing neurons of the Edinger-Westphal nucleus. We investigated whether repeated ethanol exposure affects Ucn1 and Ucn1-responsive corticotropin-releasing factor type-2 receptors (CRF2).

METHODS

Male C57BL/6J and DBA/2J mice were exposed to 2 g/kg ethanol via intraperitoneal injection once per day for 14, seven, or zero days. Ucn1 immunoreactivity was measured in the lateral septum, dorsal raphe, and Edinger-Westphal nucleus. In a separate experiment, C57BL/6J mice were exposed to ethanol for seven, one, or zero days, and CRF2 receptor binding was measured in the lateral septum and dorsal raphe by receptor autoradiography.

RESULTS

Ethanol exposure induced parallel changes in Ucn1 immunoreactive terminal fibers in the lateral septum and dorsal raphe of both strains. Seven ethanol exposures but not one ethanol exposure significantly increased CRF2 receptor binding in the dorsal raphe and slightly increased CRF2 receptor binding in the lateral septum.

CONCLUSIONS

These results provide evidence that the Ucn1/CRF2 receptor system can be modified by ethanol exposure. They additionally suggest that this system may be involved in behavioral changes during alcoholism.

Urocortin 1 in the dorsal raphe regulates food and fluid consumption, but not ethanol preference in C57BL/6J mice

The midbrain-localized Edinger-Westphal nucleus is a major site of production of urocortin 1. Urocortin 1 is a neuropeptide related to corticotropin-releasing factor that has high affinity for corticotropin-releasing factor type-1 and corticotropin-releasing factor type-2 receptors. In several mouse models, the amount of urocortin 1 neurons within the Edinger-Westphal nucleus is positively associated with ethanol preference. Central administration of urocortin 1 exerts potent anorectic actions, and implicates endogenous urocortin 1 in the regulation of food intake. It is possible that brain areas such as the dorsal raphe, which receives urocortin 1 from the Edinger-Westphal nucleus and highly expresses corticotropin-releasing factor type-2 receptors, mediate the actions of urocortin 1 on feeding and ethanol preference. In this study the amount of food, water and ethanol consumed over the dark cycle by ethanol-preferring C57BL/6J mice was measured after injection of artificial cerebrospinal fluid vehicle, urocortin 1, corticotropin-releasing factor and the corticotropin-releasing factor type-2 receptor-selective antagonist antisauvagine-30 onto the dorsal raphe. Compared with vehicle, corticotropin-releasing factor and antisauvagine-30, urocortin 1 induced a significant reduction in the amount of food consumed overnight. Also, compared with antisauvagine-30 treatment, urocortin 1 significantly reduced the amount of weight gained during this time. Urocortin 1 also significantly reduced the total amount of fluid consumed, but did not alter ethanol preference, which was high during all treatments. These results suggest that the dorsal raphe is a neuroanatomical substrate of urocortin 1-induced reductions in feeding, possibly through modulation of serotonergic activity from this nucleus. In addition, it is suggested that endogenous urocortin 1 in this area, such as from the Edinger-Westphal nucleus, does not regulate ethanol preference in C57BL/6J mice.

Expression of c-Fos in the mouse Edinger-Westphal nucleus following ethanol administration is not secondary to hypothermia or stress

Restraint stress, lipopolysaccharide (LPS), and ethanol (EtOH) administration have all been found to induce c-Fos in the brain, and to cause hypothermia. The present study was designed to assess whether the c-Fos expression that occurs in the Edinger-Westphal nucleus (EW) after EtOH administration is independent of the hypothermia or any stress effects that occur. To test this, we used restraint stress and LPS in addition to EtOH, and also examined two control areas, the dorsal raphe nucleus (DRN) and the periaqueductal gray (PAG), in addition to EW. Male C57BL6/J mice were used. Groups of mice received intraperitoneal (IP) injections of EtOH (2 g/kg), LPS (600 microg/kg or 50 microg/kg), or saline. A separate group of mice received no injection, but were placed in plastic restrainers for the entirety of the experiment. For all groups, core temperatures were monitored rectally every 30 min for 3 h postinjection, after which, the animals were sacrificed. Then, the number of Fos-positive cells in the brain regions of the EW, DRN, and PAG was quantified. Both EtOH and restraint stress induced a transient hypothermia, where core temperature (Tc) declined immediately and then rose again. Both doses of LPS induced a slower developing, longer lasting hypothermia, while saline had no effect on Tc. Only EtOH induced a significant amount of c-Fos in EW, while both doses of LPS and restraint stress induced c-Fos in DRN, and only restraint stress caused induction in PAG. These data demonstrate that activation of EW after EtOH is unrelated to hypothermia or stress.