THE EFFECTS OF AN IRREVERSIBLE DOPAMINE-RECEPTOR ANTAGONIST, N-ETHOXYCARBONYL-2-ETHOXY-1,2-DIHYDROQUINOLINE (EEDQ), ON THE REGULATION OF MUSCLE TONE IN THE RAT - THE ROLE OF THE SUBSTANTIA-NIGRA

Recent evidence has questioned the view that the increased muscle tone of Parkinson's disease results solely from reduced release of dopamin e in the striatum, by emphasising the important role of the substantia nigra. The aim of the current study was to compare the effects on mus cle tone of inactivating D-1 and D-2 dopamine receptors throughout the brain with those seen following their inactivation only in the substa ntia nigra. Inactivation of dopamine receptors by N-ethoxycarbonyl-2-e thoxy-1,2-dihydroquinoline injected either intraperitoneally, or bilat erally into the substantia nigra, resulted in similar increases in mus cle tone, measured as changes in tonic electromyographic (EMG) activit y. The magnitude and onset of EMG increases was related to the level o f dopamine receptor inactivation. The results are consistent with the hypothesis that nigral dopamine mechanisms play a key role in the main tenance of muscle tone. (C) 1998 Published by Elsevier Science Ireland Ltd. AII rights reserved.