Administration of the glutamate uptake inhibitor L-trans-PDC in the globuspallidus and the substantia nigra, but not in the striatum, attenuates thepsychostimulant effect of high helium pressure on locomotor activity in the rat

High helium pressure of more than 2 MPa produces central neuroexcitatory mo tor behavior. In rodents. symptoms comprise locomotor and motor activity (L MA), myoclonia, and, at pressure greater than 9-10 MPa, convulsions and ton ic-clonic seizures. We studied the behavioral effects of bilateral injectio n of the glutamate uptake inhibitor L-trans-pyrollidine-2,4-dicarboxylic ac id (L-trans-PDC), in either the substantia nigra reticulata (SNr), the glob us pallidus (GP), or the striatum on high helium pressure-induced LMA and m yoclonia. Injection of L-trans-PDC in the GP and the SNr attenuated LMA, wh ereas injection in the striatum enhanced it. Alternatively, injection of L- trans-PDC in the SNr increased myoclonia, whereas injection in the GP or th e striatum showed no effects on myoclonia. These results confirm that heliu m pressure-induced LMA and myoclonia have different neural origins. Accordi ng to current thinking on basal ganglia function and previous data, it is s uggested that high helium pressure would lead to a reduction of glutamate t ransmission in the SNr that could contribute to a reduction in activity of the nigrothalamic GABA pathway and then to the occurrence of LMA. It is fur ther suggested that glutamate and DA transmissions in the striatum could ha ve synergistic, rather than antagonistic, influences on motor activity. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.