Central amygdala relaxin‐3/relaxin family peptide receptor 3 signalling modulates alcohol seeking in rats

Abstract

Alcohol use disorders are a leading cause of preventable deaths worldwide, and stress is a major trigger of relapse. The neuropeptide relaxin-3 and its cognate receptor, relaxin family peptide receptor 3 (RXFP3), modulate stress-induced relapse to alcohol seeking in rats, and while the bed nucleus of the stria terminalis has been implicated in this regard, the central nucleus of the amygdala (CeA) also receives a relaxin-3 innervation and CeA neurons densely express RXFP3 mRNA. Moreover, the CeA is consistently implicated in both stress and addictive disorders. Yohimbine precipitates relapse-like behaviour in rodents, although exactly how yohimbine induces relapse is unknown, possibly by increasing stress levels and inducing heightened cue reactivity. EXPERIMENTAL APPROACHIn the current study, we examined the effects of yohimbine (1 mg·kg À1 , i.p.) on anxiety-like behaviour in alcohol-experienced rats. Furthermore, we assessed CeA neuronal activation following yohimbine-induced reinstatement of alcohol seeking and the role of the relaxin-3/RXFP3 signalling within the CeA in yohimbine-induced reinstatement to alcohol seeking. KEY RESULTSLow-dose yohimbine was anxiogenic in rats with a history of alcohol use. Furthermore, yohimbine-induced reinstatement of alcohol seeking increased Fos activation in CeA corticotrophin-releasing factor, dynorphin and GABA neurons compared with naïve and vehicle controls. Bilateral intra-CeA injections of the selective RXFP3 antagonist, R3(B1-22)R, attenuated yohimbine-induced reinstatement of alcohol seeking. CONCLUSIONSCollectively, these data suggest that the CeA is a node where yohimbine acts to induce reinstatement of alcohol seeking and implicate the relaxin-3/RXFP3 system within the CeA in this process. AbbreviationsAUD, alcohol use disorders; BNST, bed nucleus of the stria terminalis; CeA, central nucleus of the amygdala;

Characterization of the relaxin family peptide receptor 3 system in the mouse bed nucleus of the stria terminalis

“…Thus, BNST RXFP3+ cells may be implicated in stress circuitry via CRF afferent activity. Indeed, at a systems level, stress‐induced release of endogenous CRF may activate relaxin‐3 neurons within the nucleus incertus (Ma, Blasiak, Olucha‐Bordonau, Verberne, & Gundlach, ; Walker et al, ) to precipitate relapse to alcohol‐seeking via activation of upstream RXFP3+ neurons within the BNST (Ryan et al, ) and central amygdala (Walker, Kastman, Krstew, Gundlach, & Lawrence, ).…”

Pattern of neural activation following yohimbine‐induced reinstatement of alcohol seeking in rats

“…Behavioural studies were performed in accordance with the Prevention of Cruelty to Animals Act (2004), under the guidelines of the National Health and Medical Research Council Code of Practice for the Care and Use of Animals for Experimental Purposes in Australia (2013) and approved by The Florey Animal Ethics Committee. Ethanol preferring rats were utilized as they consistently obtain high levels of voluntary alcohol self‐administration and preference, and drink pharmacologically relevant quantities of alcohol (Walker, Kastman, Koeleman, et al., ; Walker, Kastman, Krstew, et al., ).…”

“…Male iP rats (250–300 g) were trained to self‐administer alcohol [10% (v./v)] under operant conditions using a fixed ratio of 3 (FR3) schedule during 20 min sessions as previously described in (Kastman, Blasiak, Walker, Siwiec & Krstew, ; Walker, Kastman, Krstew, et al., ). Two levers were available during the session, one that delivered a 100 μl alcohol reward (active lever) and the other that delivered 100 μl of water (water lever).…”

“…Alcohol experienced rats were then randomly divided into three groups; group 1 ( n = 6) where reinstatement of alcohol seeking was measured in rats during a 20‐min operant session, 30 min following administration of yohimbine (1 mg/kg, i.p.) as previously described (Walker, Kastman, Krstew, et al., ). Group 2 ( n = 6) were administered yohimbine (1 mg/kg, i.p.)…”

“…Group 3 ( n = 7) were administered vehicle (1 ml/kg, i.p.) and placed into their home‐cage, whereas group 4 (alcohol naïve, n = 6) did not receive any intervention (Kastman et al., ; Walker, Kastman, Krstew, et al., ).…”