An analysis of the bursting behaviour of the aplysia r 15 neurone during exposure to normoxia and hypoxia with and without external calcium present

Abstract

1. 1. Membrane potentials ( E M, interburst intervals (IBI), burst durations (BD), the numbers of spikes within a burst, and the amplitudes of the burst pacemaker potentials (BPP) were measured in two groups ( N = 7 per group) of R 15 neurones under conditions of 20, 10 and 5% oxygen and under nitrogen equilibration in suffusates with either Ca 2+ (10 mM) or Mg 2+ (10 mM) present (Groups I and II). 2. 2. Under normal extracellular Ca 2+ conditions, E M and the amplitude of the BPP for Group I R 15 neurones increased progressively during hypoxia and reoxygenation. 3. 3. In the absence of external calcium, the normal bursting pattern of Group II R 15 neurones was interrupted. No consistent relationships were observed among BD, IBI, and the number of spikes per burst with respect to E M or BPP. 4. 4. Hypoxia may alter the resting permeability of R 15 to potassium as well as having ephaptic effects.