Journal of Neuroscience, Vol 8, 3929-3936, Copyright © 1988 by Society for Neuroscience
A local circuit interaction in the flight system of the locust
RM Robertson and DN Reye
Department of Biology, McGill University, Montreal, Quebec, Canada.
Most of the interneurons that have been identified in the locust flight
system to date are spiking, intersegmental interneurons and the described
interactions between them are spike-mediated postsynaptic potentials. We
wished to discover whether the same interneurons also communicate via
subthreshold interactions to form local circuits independent of their
spike-mediated connections. Using a deafferented flight preparation of the
locust and glass microelectrodes, we recorded simultaneously from the
neuropil segments of different interneurons within a single thoracic
ganglion. Interneuron 301 had an indirect connection with the contralateral
301 and an indirect connection feeding back to itself. The feedback circuit
could be activated with subthreshold stimuli. Spikes in a 301 affected self
and contralateral partner, whereas subthreshold stimuli affected only self.
Thus, this paper demonstrates the existence of 2 pathways from a single
interneuron that can be functionally separate depending on whether activity
in the interneuron is subthreshold or suprathreshold for spiking. The
results show that dendritic regions of spiking intersegmental interneurons
in the locust can participate in local circuits whose operation could have
a considerable role to play in neural integration.