Journal of Neuroscience, Vol 8, 2875-2886, Copyright © 1988 by Society for Neuroscience
Control by an identified modulatory neuron of the sequential expression of plateau properties of, and synaptic inputs to, a neuron in a central pattern generator
F Nagy, PS Dickinson and M Moulins
Laboratoire de Neurobiologie et Physiologie Comparees, Arcachon, France.
Recordings from the lateral gastric (LG) neuron, which forms part of the
gastric mill central pattern generator in the red lobster, Palinurus
vulgaris, indicate that regenerative membrane properties (plateau
properties) and synaptic inputs interact sequentially rather than
simultaneously to determine its discharge pattern. LG thus presents a
composite discharge, consisting of 2 separate segments of firing and one
silent period. The first firing segment depends on regenerative membrane
properties; this is the endogenous component, or segment, of LG's
discharge. The second firing segment is the result of extrinsic synaptic
input, forming the synaptic component of LG's discharge. The relative
importance of these 2 components can vary, and thus LG's discharge ranges
from one in which LG fires only as a result of its endogenous component to
one in which its endogenous component is entirely absent and only the
synaptic component underlies action potentials. Activity in an identified
modulatory neuron suppresses the endogenous segment and enhances the
synaptic segment of LG's discharge. This long-lasting effect in turn
changes phase relationships within the gastric mill network and provides
mechanisms for producing flexibility in the gastric pattern generator and
for ensuring that a specific motor output is generated by a flexible neural
network.