Effects of clonidine and BS 100-141 on the EEG sleep pattern in rats

The effects of the peripheral and central alpha-adrenoceptor stimulant and antihypertensive agents clonidine and BS 100-141 (N-amidino-2[2,6-dichlorophenyl]acetamide - HCl) on EEG sleep patterns in rats and on blood pressure in pithed rats have been investigated. Whereas both compounds abolished paradoxical sleep (PS), clonidine, in contrast to BS 100-141, markedly increased the sleeping time. Both drugs caused a dose-dependent increase in the blood pressure of pithed rats. The pressor action was abolished by the alpha-adrenoceptor blocking agent phentolamine, but was not influenced by reserpine, indicating a direct stimulation of vascular alpha-adrenoceptors by both drugs. It is suggested that sedation or sleep induction by adrenergic drugs cannot be explained exclusively by an action on central alpha-adrenoceptors. Rather, the findings suggest that such an action may be involved in the modulation of PS.