Phase-shifting of a neuronal circadian pacemaker in Bulla gouldiana by pentylenetetrazol.

1. The convulsant agent pentylenetetrazol generates compound action potential activity from the circadian pacemaker cells in the Bulla retina. 2. The phase response curve to 3 hr pulses of pentylenetetrazol consists of only phase delays which occur following pulses delivered in the early subjective night. 3. Phase shifts to pentylenetetrazol are independent of extracellular calcium since they persist in a low-calcium EGTA solution.