Journal of Neuroscience, Vol 9, 3657-3664, Copyright © 1989 by Society for Neuroscience
Selective formation and modulation of electrical synapses between cultured Aplysia neurons
GM Carrow and IB Levitan
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
When dissociated neurons from the mollusc, Aplysia californica, are placed
in primary cell culture, they form electrical synapses in a specific, yet
alterable, manner. Pairs of neurons from the same ganglion
("homoganglionic" pairs) form electrical synapses with high coupling
coefficients. This is due to relatively high macroscopic junctional
conductance as determined directly by voltage clamping both neurons of each
pair. By contrast, synapses between pairs of neurons from different ganglia
("heteroganglionic" pairs) exhibit lower coupling coefficients as a result
of lower macroscopic junctional conductance. Both types of junction are
nonrectifying, not gated by voltage, and resistant to uncoupling by octanol
and heptanol. This dichotomy of synaptic efficacy is altered upon exposure
of the neurons to the lectin, conacanavalin A (Con A). Acute treatment of
heteroganglionic cell pairs with Con A increases their junctional
conductance to the higher level characteristic of homoganglionic pairs
within several hours. However, the higher junctional conductance of
homoganglionic pairs is not modulated by Con A. The results presented here
suggest that synaptic specificity among these regenerating neurons may be
mediated at least in part by ganglion-specific cell-recognition molecules.
Furthermore, these molecules may be, or may be linked to, lectin receptors
that regulate gap junction channels.