BRAIN ACETYLCHOLINE LEVELS AND INHIBITION OF THE TAIL-FLICK REFLEX IN MICE

¹ Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina

Levels of whole brain "bound" acetylcholine were determined in mice by a gas chromatographic method. Various narcotic analgesics, narcotic antagonists and centrally acting cholinergic drugs alone or in combination were simultaneously tested for their effects on the inhibition of the tail-flick reflex and levels of acetylcholine. The possibility of a correlation between analgesia, as measured by inhibition of the tail-flick reflex, and levels of bound acetylcholine was examined. For oxotremorine a relationship did exist between the levels of acetylcholine and the inhibition of the tail-ifick reflex. Within the series of compounds studied, a clear relationship between this test and the levels of acetylcholine was not found. Although no clear correlation existed, certain trends became evident which merited further investigation. An apparent tolerance in the tail-ifick test to the centrally active cholinergic oxotremorine was demonstrated. A cross-tolerance between oxotremorine and morphine was not found.

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