Contrasting local effects of MAO inhibitors on caudate tremor activities.

Hindlimb tremor was produced in chronic cats by intracaudate microinjection of the monoamine oxidase (MAO) inhibitors tranylcypromine and harmaline throughout a range of doses (150-385 mug). Pargyline, however, was non-tremorgenic within the same range, suggesting that interference with MAO is not sufficient in itself to elicit tremor. Tranylcypromine tremors differed from those of harmaline by exhibiting a slower onset, longer duration and susceptibility to antagonism by hemicholinium. In contrast, ongoing cholinergic tremors following intracaudate physostigmine were variably suppressed by all three MAO inhibitors at comparable dose levels (175-200 mug); pargyline produced the most complete suppression. These results indicate that MAO inhibitors can modify tremor activities in a differential manner dependent both on the functional state of the caudate nucleus and on the ability of cartain MAO inhibitors to exert other local actions.