SELF-RECOGNITION - A CONSTRAINT AN THE FORMATION OF ELECTRICAL COUPLING IN NEURONS

Electrical coupling between specific neurons is important for proper f unction of many neuronal circuits. Identified cultured neurons from th e snail Helisoma show a strong correlation between electrical coupling and presence of gap junction plaques in freeze-fracture replicas. Gap junction plaques, however, were never seen between overlapping neurit es from a single neuron, even though those same neurites formed gap ju nctions with neurites from another essentially identical identified ne uron. This observation suggests that a form of self-recognition inhibi ts reflexive gap junction formation between sibling neurites. When one or both of those growth cones had been physically isolated from the n euronal cell body, both electrical coupling and gap junction plaques, between growth cones from the same neuron, were observed to form rapid ly (within 30 min). Thus, inhibition of electrical coupling between si bling neurites apparently depends on cytoplasmic continuity between ne urites, and not the molecular composition of neurite membrane. The for mation of gap junctions is not likely due to the isolation process; ra ther, the physical isolation appears to release an inhibition of refle xive gap junction formation. These data demonstrate the existence of a previously unknown constraint on the formation of electrical synapses .