MODULATION BY GABA TRANSMISSION IN THE SUBSTANTIA-NIGRA COMPACTA AND RETICULATA OF LOCOMOTOR-ACTIVITY IN RATS EXPOSED TO HIGH-PRESSURE

HELIUM pressure of >20 bar causes neuroexcitatory changes referred to as the high pressure neurological syndrome. In rodents, symptoms inclu de locomotor and motor activity (LMA), myoclonia and, at greater press ure, convulsions. We studied the effects of the GABA reuptake inhibito r nipecotic acid, the GABA transaminase inhibitor gamma-vinyl-GABA (GV G), the GABA(A) receptor agonist muscimol, and the GABA(B) receptor ag onist baclofen. Whatever the drug used, bilateral administration in th e substantia nigra reticulata (SNR) or in the substantia nigra compact a (SNC) showed no significant effects on myoclonia. In contrast, admin istration in the SNR of nipecotic acid, GVG, and baclofen resulted in a significant decrease of LMA; administration of muscimol in the SNR i ncreased LMA. No significant effect was seen when drugs were injected in the SNC. These results suggest that changes in GABA transmission in the SNR, but not in the SNC, play a crucial role in the control of mo tor activity and the regulation of movement. (C) 1998 Rapid Science Lt d.