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

The effects of the peripheral and central α-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 increased in the blood pressure of pithed rats. The pressor action was abolished by the α-adrenoceptor blocking agent phentolamine, but was not influenced by reserpine, indicating a direct stimulation of vascular α-adrenoceptors by both drugs. It is suggested that sedation or sleep induction by adrenergic drugs cannot be explained exclusively by an action on central α-adrenoceptors. Rather, the findings suggest that such an action may be involved in the modulation of PS.