Effect of xylocaine and carbachol applied to the caudate nucleus of rats on barbiturate sleeping time.

Since lesion of subcortical structures may affect the barbiturate sleeping time (bST), we decided with the present study to elucidate the role of the caudate nucleus in the determination of central sensitivity to barbiturates. Rats implanted with a cannula in the caudate nucleus of one or both sides, as well as with a jugular cannula, were utilized. Intravenous injections of sodium pentobarbital (40 mg/kg), intracerebral injections of Xylocaine (0.04 microgram), carbachol (0.2 micrograms) or artificial cerebrospinal fluid (ACF) into the caudate nucleus were performed. Both Xylocaine and carbachol, but not ACF, increased the bST regardless of the preparation used, the only exception being Xylocaine which did not alter the bST, if injected into the left caudate nucleus. The results suggest that the caudate nucleus may act as a modulator of the central sensitivity to barbiturates.