Mechanism of Action of Nitrogen Pressure in Controlling Striatal Dopamine Level of Freely Moving Rats is Changed by Recurrent Exposures to Nitrogen Narcosis.

Lavoute, Cécile; Weiss, Michel; Risso, Jean-Jacques; Rostain, Jean-Claude

In rats, a single exposure to 3 MPa nitrogen induces change in motor processes, a sedative action and a decrease in dopamine release in the striatum. These changes due to a narcotic effect of nitrogen have been attributed to a decrease in glutamatergic control and the facilitation of GABAergic neurotransmission involving NMDA and GABA receptors, respectively. After repeated exposure to nitrogen narcosis, a second exposure to 3 MPa increased dopamine levels suggesting a change in the control of the dopaminergic pathway. We investigated the role of the nigral NMDA and GABA receptors in changes in the striatal dopamine levels. Dopamine-sensitive electrodes were implanted into the striatum under general anesthesia, together with a guide-cannula for drug injections into the SNc. Dopamine level was monitored by in vivo voltammetry. The effects of NMDA/GABA receptor agonists (NMDA/muscimol) and antagonists (AP7/gabazine) on dopamine levels were investigated. Rats were exposed to 3 MPa nitrogen before and after five daily exposures to 1 MPa. After these exposures to nitrogen narcosis, gabazine, NMDA and AP7 had no effect on the nitrogen-induced increase in dopamine levels. By contrast, muscimol strongly enhanced the increase in dopamine level induced by nitrogen. Our findings suggest that repeated nitrogen exposure disrupted NMDA receptor function and decreased GABAergic input by modifying GABA receptor sensitivity. These findings demonstrated a change in the mechanism of action of nitrogen at pressure.

GABA receptors; NEURAL transmission; DOPAMINE; LABORATORY rats; BASAL ganglia; VOLTAMMETRY; METHYL aspartate receptors; PHYSIOLOGICAL effects of nitrogen; ANESTHESIA

Neurochemical Research, 2012, Vol 37, Issue 3, p655

0364-3190

Academic Journal

10.1007/s11064-011-0657-1