Phase shifting the circadian rhythm of neuronal activity in the isolated Aplysia eye with puromycin and cycloheximide. Electrophysiological and biochemical studies.

Abstract

The effects of pulse application of puromycin (PURO) or cycloheximide (CHX) were tested on the circadian rhythm (CR) of spontaneous compound action potential (CAP) activity in the isolated Aplysia eye. CAP activity was recorded from the optic nerve in constant darkness at 15.degree. C. PURO pulses (6, 12 h; 12-134 .mu.g/ml) and CHX pulses (12 h, 500-2000 .mu.g/ml) caused dose-dependent phase delays in the CR when administered during projected night. PURO pulses (6 h, 125 .mu.g/ml) caused phase advances when given during projected day and caused phase delays when given during projected night. In biochemical experiments PURO (12 h, 20 .mu.g/ml) and CHX (12 h, 500 .mu.g/ml) inhibited leucine incorporation into the eye by .apprx. 50%. PURO (12 h; 20, 125 .mu.g/ml) also changed the molecular weight distribution of proteins synthesized by the eye during the pulse. The effect of PURO (12 h, 125 .mu.g/ml) on the level of incorporation was almost completely reversible within the next 12 h but the phase-shifted eye showed an altered spectrum of proteins for up to 28 h after the pulse. In electrophysiological experiments spontaneous CAP activity and responses to light were measured before, during, and after drug treatments. In all, 8 parameters in 3 periods were analyzed quantitatively. Of these 24 indices, only 3 showed significant changes. PURO increased spontaneous CAP frequency by 67% 0-7 h after the drug pulse and increased the CAP amplitude of the tonic light response by 23% > 7 h after the pulse. CHX increased the intraburst spontaneous CAP frequency by 33% during the pulse and CAP frequency of the tonic light response by 32% 0-7 h after the pulse. Phase-shifting doses of PURO and CHX probably inhibit protein synthesis in the eye without causing adverse electrophysiological effects. Protein synthesis may be involved in the production of the CR of the isolated Aplysia eye.