The anesthetic agents pentobarbital and chloralose block phase shifts of a neuronal in vitro circadian pacemaker

Abstract

The anesthetic pentobarbital (6 mM) is capable of blocking light or high K(+)-induced phase shifts of the circadian pacemaker in the isolated eye of Bulla. Pentobarbital alone was effective in generating phase shifts consistent with phase response curves obtained to either extracellular low Ca2+ or hyperpolarizing pulses. Patch clamp recordings from the circadian pacemaker cells indicate that pentobarbital reduces the Ca(2+)-dependent K+ current. Together, these data suggest that pentobarbital acts on the pacemaker by reducing an inward Ca2+ current. Chloralose (3 mM) was effective in blocking light, but not high K(+)-induced phase shifts, and did not generate phase shifts when applied alone, suggesting that chloralose may act as a weak Ca2+ channel inhibitor.