L-type calcium channels modulate glutamate-driven bursting activity in the nucleus accumbens in vivo.
The majority of adult nucleus accumbens medium spiny neurons exhibit a bistable membrane potential that fluctuates between a relatively hyperpolarized (Down) state (average=-76 mV) and a less hyperpolarized (Up) state (average=-60 mV) near firing threshold. During in vivo extracellular recordings from nucleus accumbens neurons, we used microiontophoresis to apply glutamate and selected neurons that fired in bursting patterns reflecting a subthreshold bistable membrane potential. The average frequency of bursts events was 0.85 Hz. The average burst duration was 392+/-3.5 ms, with an average of 13.4 spikes and an average spike frequency of 30.6+/-3.1 Hz per burst. To determine the involvement of the L-type calcium channel in the bursting pattern, we applied the benzothiazepine L-type calcium channel blocker, diltiazem. Diltiazem rapidly (<2 min) and reversibly decreased the burst duration by 29% and the frequency of spikes within a burst by 30% without changing the overall burst event frequency. The results provide the first in vivo electrophysiological evidence implicating an L-type calcium channel that modulates glutamate-induced burst firing of nucleus accumbens neurons.
Cooper
D C
DC
Department of Neuroscience, Finch University of Health Sciences, The Chicago Medical School, 3333 Green Bay Rd, North Chicago, IL 60064, USA.
White
F J
FJ
D000818:Animals; D020746:Calcium Channels, L-Type / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology*; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D007478:Iontophoresis; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009714:Nucleus Accumbens / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
D020746:Calcium Channels, L-Type; D018698:Glutamic Acid; D004110:Diltiazem