PT  - JOURNAL ARTICLE
AU  - Scott C. Steffensen
AU  - Adena L. Svingos
AU  - Virginia M. Pickel
AU  - Steven J. Henriksen
TI  - Electrophysiological Characterization of GABAergic Neurons in the Ventral Tegmental Area
AID  - 10.1523/JNEUROSCI.18-19-08003.1998
DP  - 1998 Oct 01
TA  - The Journal of Neuroscience
PG  - 8003--8015
VI  - 18
IP  - 19
4099  - http://www.jneurosci.org/content/18/19/8003.short
4100  - http://www.jneurosci.org/content/18/19/8003.full
SO  - J. Neurosci.1998 Oct 01; 18
AB  - GABAergic neurons in the ventral tegmental area (VTA) play a primary role in local inhibition of mesocorticolimbic dopamine (DA) neurons but are not physiologically or anatomically well characterized. We used in vivo extracellular and intracellular recordings in the rat VTA to identify a homogeneous population of neurons that were distinguished from DA neurons by their rapid-firing, nonbursting activity (19.1 ± 1.4 Hz), short-duration action potentials (310 ± 10 μsec), EPSP-dependent spontaneous spikes, and lack of spike accommodation to depolarizing current pulses. These non-DA neurons were activated both antidromically and orthodromically by stimulation of the internal capsule (IC; conduction velocity, 2.4 ± 0.2 m/sec; refractory period, 0.6 ± 0.1 msec) and were inhibited by stimulation of the nucleus accumbens septi (NAcc). Their firing rate was moderately reduced, and their IC-driven activity was suppressed by microelectrophoretic application or systemic administration of NMDA receptor antagonists. VTA non-DA neurons were recorded intracellularly and showed relatively depolarized resting membrane potentials (−61.9 ± 1.8 mV) and small action potentials (68.3 ± 2.1 mV). They were injected with neurobiotin and shown by light microscopic immunocytochemistry to be multipolar cells and by electron microscopy to contain GABA but not the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH). Neurobiotin-filled dendrites containing GABA received asymmetric excitatory-type synapses from unlabeled terminals and symmetric synapses from terminals that also contained GABA. These findings indicate that VTA non-DA neurons are GABAergic, project to the cortex, and are controlled, in part, by a physiologically relevant NMDA receptor-mediated input from cortical structures and by GABAergic inhibition.