Nickel induces oscillatory behavior and enhanced synaptic and electrotonic transmission between stomatogastric neurons of Panulirus interruptus

Abstract

The pyloric pattern generator network of the stomatogastric ganglion uses a mixture of burst-inducing plateau potentials, synaptic transmission, and electrical coupling to produce its patterned output. This study examines the effects of two divalent, calcium channel blockers, nickel and cadmium, on voltage oscillations, synaptic transmission, and electrical coupling between the two pyloric dilator (PD) neurons and lateral pyloric (LP) neuron of Panulirus interruptus. The in vitro stomatogastric ganglion was bathed in saline containing tetrodotoxin (TTX) to eliminate Na-spikes and the spontaneous voltage oscillations of the pyloric rhythm, resulting in a steady resting potential. Addition of 50–100 μ M Ni 2+ to the TTX-saline induced voltage oscillations of similar amplitude and frequency as the endogenous rhythmic activity (before the application of TTX). 25–50 μM nickel enhanced graded synaptic transmission and electrical coupling and altered voltage waveforms, while producing little change in the input resistance measured in the soma. 10–1000 μM Cd 2+ acted as a dose-dependent blocker of graded synaptic transmission, but had no other detectable effects. We propose that nickel, in contrast to cadmium, exerts a modulator-like effect deep in the pyloric neuropil.