Dynamical aspects of in vitro conditioning in Hermissenda type B photoreceptor

Dynamics of changes in physiology and morphology were studied in Hermissenda photoreceptors after in vitro conditioning with paired light and vibration. An increase in input resistance of the type B photoreceptor was observed following 5 paired presentations of light and vibration. It peaked at 10 min after in vitro conditioning, then decreased to a level twice the pre-conditioning level for more than 60 min. Contraction of the terminal branches along centro-lateral direction was initiated 5 min after conditioning and reached its final state at 10 min after conditioning. The pairing specific contraction of the axon terminal was not observed in ASW containing anisomycin. The dynamics in physiology and morphology were completely parallel 30 min after conditioning. These findings suggested that in vitro conditioning induced contraction was dependent on protein synthesis dependent process initiated within 5 min after training trials and that the change of cell morphology is a form of short-term synaptic plasticity that involves changes in macromolecular synthesis. Present findings that functional remodeling at the terminal branch of the type B photoreceptor occurred within 10 min after conditioning was the fastest modification process reported so far.