EFFECTS OF -METHYL-meta-TYROSINE ON SPONTANEOUS AND CAUDATE-INDUCED ELECTROENCEPHALOGRAM ACTIVITY AND REGIONAL CATECHOLAMINES IN THE CAT BRAIN

¹ Department of Pharmacology, University of Kansas Medical Center, Kansas City, Kansas

Electroencephalogram (EEG) recordings were made from conscious cats, paralyzed with gallamine, which were subsequently sacrificed with samples being taken for assay of norepinephrine (NE) and dopamine (DA). It was demonstrated that -methyl-meta-tyrosine (-MMT) at 100, 70 and 30 mg/kg produced markedly different depleting effects which were dependent both upon the amine and the area measured. Hypothalamic NE was most resistant to depletion by all doses but an inverse dose-effect relationship was found with DA in this region since the 30 mg/kg dose was more effective than the higher doses. All three doses of -MMT produced extreme EEG activation and attenuation of caudate-induced slowing and spindling in the EEG. The 100 and 70 mg/kg doses tended to produce complete blockade of these synchronizing influences in most animals. This block was found not to be associated with depletion but was dependent upon presence of NE and DA stores and probably upon presence of the metabolites of -MMT. The evidence suggests that the effects of -MMT depend upon the release of one or both catecholamines but that caudate DA and hypothalamic NE may be excluded. The possibility that DA release is of primary importance is discussed in context with this and other data.