Fig. 6.

Effects of clonidine (2 μg/kg, i.v.) on the spontaneous discharge of an LC cell. Clonidine produced an 86% reduction in the discharge of this cell 10 min after injection as compared to its immediate pre-drug level. Clonidine reduced discharge for about 45 min. The reduction of discharge by clonidine, a consequence of α₂ receptor activation, is characteristic of noradrenergic cells. Insert: average discharge rate (mean ± S.E.M.) before and after clonidine administration in the seven cells tested. Baseline discharge rates were taken during the 10 min period before drug administration in QW. The effect of clonidine was assessed 10–30 min (i.v.; n = 6) or 1 h (oral; n = 1) after drug administration during QW. * denotes significant difference (P < 0.001, paired t-test) in firing rate between baseline and post-drug condition.