Journal of Neurophysiology, Vol 69, Issue 1 293-296, Copyright © 1993 by APS

ARTICLES

Spike-like potentials in the axons of nonspiking photoreceptors

M. Weckstrom, M. Jarvilehto and K. Heimonen
Department of Physiology, University of Oulu, Finland.

1. The voltage responses to light of dark-adapted cockroach photoreceptors were recorded from the somata in the retina and the axons below the two basement membranes. 2. One or more spike-like fast depolarizations superimposed on the graded receptor potential were recorded in photoreceptor axons identified by Lucifer yellow injections. These spikes are voltage dependent in as much as they could be elicited with depolarizing current pulses as well as with light stimuli. In photoreceptor somata only graded receptor potentials were recorded. 3. The physiological function of these axonal spikes may be to serve as an amplification mechanism that counteracts the unfavorable combination of photoreceptor geometry and electrical properties.

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