THE RELEASE OF ACETYLCHOLINESTERASE IN-VIVO IS REGULATED BY DOPAMINERGIC SYSTEMS IN THE GUINEA-PIG SUBSTANTIA-NIGRA

Acetylcholinesterase (AChE) and dopamine are both stored and released from dendrites within the substantia nigra: however, it is as yet unkn own whether the regulation of these two purported neuromodulators is i n any way related. Using a sensitive chemiluminescent system to monito r AChE release 'on-line', the effects of inhibiting synthesis and stor age of dopamine with cc-methyl-p-tyrosine (AMPT: 250 mg/kg, i.p.) and reserpine (6 mg/kg, i.p.), respectively, have been studied. Both these agents significantly reduced nigral tissue dopamine levels by decreas es of 83% and 63%, respectively: however, only AMPT had a significant effect in vivo on the spontaneous release of AChE compared to consciou s control animals (66% decrease). Co-application of both AMPT and rese rpine resulted in a significant decrease in the tissue dopamine conten t (95%) and in spontaneous release of AChE compared to conscious contr ol guinea-pigs (72%); however, these effects were not significantly di fferent from when AMPT was employed alone. Application of potassium io ns (60 mM) or veratridine (100 mu M) both evoked release of AChE in co ntrol animals : however, when expressed as a percentage of basal level s, this increase in release was not influenced by drug treatment or st ate of consciousness. These results suggest that de novo dopamine synt hesis may at least in part, have an influential effect on release (and possibly storage) of AChE in the substantia nigra.