Abstract
The striatum consists mainly of principal neurons, which receive excitatory cortical inputs and project to other basal ganglia structures. The interneurons of the striatum are limited, but rich in variety and complexity. For example, GABA/parvalbumin-contaning interneurons are connected each other by gap junctions, receive cortical inputs and project on the projection neurons. To clarify the functions of the GABAergic interneurons in the striatum, we studied the effect on the activity of striatal projection neurons by the blockade of GABAergic neurotransmission. Using Japanese monkeys, pairs of stimulating electrodes were implanted in the forelimb regions of the primary motor cortex (M1) and the supplementary motor area (SMA) after identification of each area by electrophysiological methods. Single-unit recordings of striatal neurons in combination with local application of drugs were performed with an electrode assembly consisting of an elgiloy microelectrode and a silica tube. The spontaneous activity and the evoked responses by M1- or SMA-stimulation were observed, and then GABAA agonist gabazine (1mM) was injected through the silica tube (0.03μL/min). The duration of excitation evoked by cortical stimulation increased after gabazine injection, while spontaneous activity remained unchanged. These results suggest that GABAergic microcircuits in the striatum have a function of feed-forward inhibition on the firing of striatal projection neurons. [Jpn J Physiol 55 Suppl:S174 (2005)]
