Abstract
The aim of the present study was to assess the effects of l-glutamate (l-GLU) on the neurophysiology of ventral tegmental A10 dopamine neurons in rat midbrain slices using extracellular and intracellular recording methods. l-Glutamate perfusion of 10-100 μM concentrations produced dose-dependent increases in firing rate, with no changes in pattern of firing, while higher concentrations led to a loss of activity reminiscent of depolarization inactivation. The extracellular changes were relfected by the pronounced membrane depolarizations observed through intracellular recordings. The effects of low doses (≦ 30 μM) of l-GLU on firing rate and membrane potential were completely antagonized by co-perfusion with the noncompetitive NMDA blocker, phencyclidine, or the selective competitive NMDA receptor antagonist, CGS 19755, but not by the selective non-NMDA blocker NBQX. However, at concentrations of ≧ 300 μM l-GLU's effects could not be completely blocked without the presence of both CGS 19755 and NBQX. Moreover, the magnitude of l-GLU-induced depolarizations became attenuated at membrane potentials more negative than -70 mV. These results suggest that in physiological-like conditions that low extracellular levels of glutamate excite midbrain dopamine neurons via a preferential activation of NMDA receptors, and that only at higher concentrations of l-GLU are non-NMDA receptors brought into play.
Original language | English (US) |
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Pages (from-to) | 299-306 |
Number of pages | 8 |
Journal | Brain Research |
Volume | 627 |
Issue number | 2 |
DOIs | |
State | Published - Nov 12 1993 |
Keywords
- Brain slice
- Electrophysiology
- Excitatory amino acid
- N-Methyl-d-aspartite acid
- Ventral tegmental area
- l-Glutamate
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- Clinical Neurology
- Developmental Biology