Role for the Rostromedial Tegmental Nucleus in Signaling the Aversive Properties of Alcohol. (8th July 2016)

• Record Type: Journal Article
• Authors: Glover, Elizabeth J.; McDougle, Molly J.; Siegel, Griffin S.; Jhou, Thomas C.; Chandler, L. Judson
• Is Part Of: Alcoholism. Volume 40:Number 8(2016)
• Page Start: 1651
• Page End: 1661
• Publication Date: 2016-07-08
• Subjects: Conditioned Taste Aversion -- Lateral Habenula -- Addiction -- Sex Differences -- cFos; Alcoholism -- Periodicals; Alcoholism -- Periodicals; Alcoolisme; Electronic journals; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 616.861005
• DOI: 10.1111/acer.13140
• Languages: English
• ISSNs: 0145-6008

Abstract

Abstract : Background: While the rewarding effects of alcohol contribute significantly to its addictive potential, it is becoming increasingly appreciated that alcohol's aversive properties also play an important role in the propensity to drink. Despite this, the neurobiological mechanism for alcohol's aversive actions is not well understood. The rostromedial tegmental nucleus (RMTg) was recently characterized for its involvement in aversive signaling and has been shown to encode the aversive properties of cocaine, yet its involvement in alcohol's aversive actions have not been elucidated. Methods: Adult male and female Long–Evans rats underwent conditioned taste aversion (CTA) procedures where exposure to a novel saccharin solution was paired with intraperitoneal administration of saline, lithium chloride (LiCl), or ethanol (EtOH). Control rats underwent the same paradigm except that drug and saccharin exposure were explicitly unpaired. Saccharin consumption was measured on test day in the absence of drug administration, and rats were sacrificed 90 to 105 minutes following access to saccharin. Brains were subsequently harvested and processed for cFos immunohistochemistry. The number of cFos‐labeled neurons was counted in the RMTg and the lateral habenula (LHb)—a region that sends prominent glutamatergic input to the RMTg. Results: In rats that received paired drug and saccharin exposure, EtOH and LiCl induced significant CTA compared to saline to a similar degree in males and females. Both EtOH‐ and LiCl‐induced CTA significantly enhanced cFos expression in the RMTg and LHb but not the hippocampus. Similar to behavioral measures, no significant effect of sex on CTA‐induced cFos expression was observed. cFos expression in both the RMTg and LHb was significantly correlated with CTA magnitude with greater cFos being associated with more pronounced CTA. In addition, cFos expression in the RMTg was positively correlated with LHb cFos. Conclusions: These data suggest that the RMTg and LHb are involved in the expression of CTA and are consistent with previous work implicating the RMTg in aversive signaling. Furthermore, increased cFos expression in the RMTg following EtOH‐induced CTA suggests that this region plays a role in signaling alcohol's aversive properties. Abstract : The neurobiological mechanism for alcohol's aversive properties is not well understood. To explore a role for the RMTg, conditioned taste aversion (CTA) was produced in rats in the paired condition in response to saccharin and i.p. drug pairings. In the unpaired condition, drug exposure and saccharin exposure were unpaired. CTA enhanced cFos expression in the RMTg and lateral habenula (LHb) but not the hippocampus. cFos correlated positively with CTA magnitude. These data suggest that the RMTg and LHb are involved in ethanol‐induced CTA.