Treatment with carbamazepine may enhance alpha 2-noradrenergic autoreceptor sensitivity.

Chronic, not acute treatment with carbamazepine enhanced the hypothermic response to a dose of clonidine thought to exert its predominant effect on the presynaptic alpha 2-autoreceptor. This response was markedly elevated both during the course of and 10 days after the discontinuation of treatment with carbamazepine. Sensitivity to clonidine returned to baseline 10 to 21 days after the discontinuation of treatment. Carbamazepine is the first treatment for the disorders of mood that has been demonstrated to enhance a physiological response to clonidine. The authors discuss the theoretical relationship between increased sensitivity of the presynaptic alpha 2-autoreceptor and the usefulness of carbamazepine in the treatment of bipolar disorder.

Chronic swim stress enhances the motoric inhibiting effects of a muscarinic agonist.

The authors previously demonstrated that chronic inescapable swim stress and footshock increase the capacity of a fixed dose of a muscarinic agonist to produce hypothermia in the rat. This project was designed to determine whether chronic inescapable swim stress in cold water would render a low dose of a muscarinic agonist, devoid of an effect on motor behavior in the naive rat (i.e., prior to subjection to the course of swim stress), an inhibitor of mobility. The study involved two groups of rats, an experimental group which received arecoline and a control group which received saline five minutes prior to being placed in an open field. Number of crossings, the dependent variable, was measured in both groups before and after a 14-day course of twice daily inescapable swim stress of 10 minutes duration at 12 degrees C. The arecoline-treated group, as hypothesized, exhibited a significantly greater reduction in number of crossings than the saline-treated groups following the course of swim stress.