Involvement of protein synthesis in circadian clock of Aplysia eye

The effects of the protein synthesis inhibitors anisomycin and puromycin were measured on protein synthesis and phase shifting of the circadian rhythm in the isolated Aplysia eye. Anisomycin pulses induce phase delays proportional in magnitude to the duration and percentage of protein synthesis inhibition. The phase-response curve to anisomycin pulses consisted of delays induced throughout the subjective night. Delays were maximal between circadian times (CT) 18 and CT 2; pulses initiated between CT 2 and CT 12 did not phase shift. Puromycin induced phase delays and advances. Delays were proportional to the duration and percentage of protein synthesis inhibition, occurring with increasing magnitude throughout the subjective night (CT 12-2). Peptidyl-puromycin formation may contribute to the magnitude of the delay. Advances, occurring between CT 2 and CT 8, required a greater drug concentration and pulse duration than delays and appeared to result from an effect other than protein synthesis inhibition. Our results support the hypothesis of a phase-dependent requirement for protein synthesis during the subjective night in this circadian clock.