Glutamatergic transmission in the central nucleus of the amygdala is selectively altered in Marchigian Sardinian alcohol-preferring rats: Alcohol and CRF effects

Abstract

The CRF system of the central nucleus of the amygdala (CeA) is important for the processing of anxiety, stress, and effects of acute and chronic ethanol. We previously reported that ethanol decreases evoked glutamate transmission in the CeA of Sprague Dawley rats and that ethanol dependence alters glutamate release in the CeA. Here, we examined the effects of ethanol, CRF and a CRF1 receptor antagonist on spontaneous and evoked glutamatergic transmission in CeA neurons from Wistar and Marchigian Sardinian Preferring (msP) rats, a rodent line genetically selected for excessive alcohol drinking and characterized by heightened activity of the CRF1 system. Basal spontaneous and evoked glutamate transmission in CeA neurons from msP rats was increased compared to Wistar rats. Ethanol had divergent effects, either increasing or decreasing spontaneous glutamate release in the CeA of Wistar rats. This bidirectional effect was retained in msP rats, but the magnitude of the ethanol-induced increase in glutamate release was significantly smaller. The inhibitory effect of ethanol on evoked glutamatergic transmission was similar in both strains. CRF also either increased or decreased spontaneous glutamate release in CeA neurons of Wistar rats, however, in msP rats CRF only increased glutamate release. The inhibitory effect of CRF on evoked glutamatergic transmission was also lost in neurons from msP rats. A CRF1 antagonist produced only minor effects on spontaneous glutamate transmission, which were consistent across strains, and no effects on evoked glutamate transmission. These results demonstrate that the genetically altered CRF system of msP rats results in alterations in spontaneous and stimulated glutamate signaling in the CeA that may contribute to both the anxiety and drinking behavioral phenotypes.