Autoradiographic studies on the effect of ethanol on muscarinic receptors in rat brain

The effect of ethanol vapour inhalation on the binding characteristics of muscarinic receptors in rat brain has been studied using quantitative autoradiography. After 14 days in ethanol vapour there was increased binding of [(3)H]QNB to the cortex of 4- and 6-week-old animals, but not 11-week-old animals, and to the hippocampus of the 6-week-old animals. Displacement studies indicated that the effect of ethanol was due to an increase in the density of low-affinity carbachol binding sites. There was no effect on the binding of [(3)H]QNB in the presence of pirenzipine. The data strongly suggest that the increase in binding after ethanol exposure is due to an increase in M(1) sites in the younger animals possibly linked to age-related plasticity of the nervous system.