Papers - Yamada, Yoshitake

Functional Roles of Action Potentials and Na Currents in Amacrine Cells

(Springer Japan)  11   55 - 58 2003

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Functional roles of receptors and ion channels in amacrine cells

The Keio Journal of Medicine 51 ( Suppl.1 ) 30 2002.08

ISSN  0022-9717

Propagation of action potentials from the soma to individual dendrite of cultured rat amacrine cells is regulated by local GABA input

Yamada, Y, Koizumi, A, Iwasaki, E, Watanabe, SI, Kaneko, A

JOURNAL OF NEUROPHYSIOLOGY (Journal of Neurophysiology)  87 ( 6 ) 2858 - 2866 2002.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0022-3077

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Retinal amacrine cells are interneurons that make lateral and vertical connections in the inner plexiform layer of the retina. Amacrine cells do not possess a long axon, and this morphological feature is the origin of their naming. Their dendrites function as both presynaptic and postsynaptic sites. Half of all amacrine cells are GABAergic inhibitory neurons that mediate lateral inhibition, and their light-evoked response consists of graded voltage changes and regenerative action potentials. There is evidence that the amount of neurotransmitter release from presynaptic sites is increased by spike propagation into the dendrite. Thus understanding of how action potentials propagate in dendrites is important to elucidating the extent and strength of lateral inhibition. In the present study, we used the dual whole cell patch-clamp technique on the soma and the dendrite of cultured rat amacrine cells and directly demonstrated that the action potentials propagate into the dendrites. The action potential in the dendrite was TTX sensitive and was affected by the local membrane potential of the dendrite. Propagation of the action potential was suppressed by local application of GABA to the dendrite. Dual dendrite whole cell patch-clamp recordings showed that GABA suppresses the propagation of action potentials in one dendrite of an amacrine cell, while the action potentials propagate in the other dendrites. It is likely that the action potentials in the dendrites are susceptible to various external factors resulting in the nonuniform propagation of the action potential from the soma of an amacrine cell.

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