Journal of Neuroscience, Vol 15, 6576-6585, Copyright © 1995 by Society for Neuroscience
Pharmacological characterization of presynaptic calcium currents underlying glutamatergic transmission in the avian auditory brainstem
S Sivaramakrishnan and G Laurent
Biology Division, California Institute of Technology, Pasadena 91125, USA.
We used whole-cell patch-clamp techniques on presynaptic terminals and
postsynaptic neurons of the glutamatergic magnocellularis synapse in the
chick auditory brainstem to study the effects of N, P, and L-type calcium
channel blockers directly on presynaptic calcium currents and transmitter
release. Presynaptic calcium currents and transmitter release were
unaffected by nifedipine, blocked partially by omega- agatoxin IVA and
completely by omega-conotoxin GVIA. The presynaptic calcium current is a
low voltage-activated, noninactivating current and its block by
omega-agatoxin IVA was not reversed by repeated depolarization of the
presynaptic terminal. Thus, the presynaptic calcium current that underlies
transmitter release at the chick magnocellularis synapse differs in some
respects from N and P-type calcium currents described in vertebrate
neuronal cell bodies.