Calcitonin gene-related peptide (CGRP) levels and alcohol.
Calcitonin gene-related peptide (CGRP) when administered into the brain exerts stress-like effects such as increased pain sensitivity, anorexia, and potentiation of fear-related behaviours. Since alcohol consumption may be related to alcohol's anxiolytic properties, the present study sought to determine if brain CGRP levels were correlated with genetic differences in preference for drinking alcohol and/or affected by alcohol exposure/withdrawal. CGRP-like immunoreactivity (CGRP-LI) was measured by radioimmunoassay (RIA) in amygdala, hippocampus, frontal cortex, hypothalamus, and caudate. In the first experiment, CGRP-LI was compared in alcohol-naive rats [preferring (P) and non-preferring (NP)], lower concentrations were found in the hippocampus (U = 153.5; d.f. = 1,28; p < 0.014) and frontal cortex (U = 183.0; d.f. = 1,28; p < 0.0001) of the P rats. In a second experiment, a group of outbred Wistar rats were exposed to alcohol in vapour chambers, or control conditions. At 7 wk of alcohol exposure there were no differences in exposed rats as compared to controls. However, at 4 wk following ethanol withdrawal, higher concentrations of CGRP-LI were found in the hippocampus (U = 26.5; d.f. = 1,20 p < 0.05), hypothalamus (U = 17.5; d.f. = 1,20; p < 0.009), and caudate-putamen (U = 17.0; d.f. = 1,20; p < 0.009) of the previously exposed animals. These studies suggest that CGRP may modulate alcohol preference and additionally, that exposure/withdrawal from ethanol produces long-lasting effects on CGRP-LI.