The effects of arecoline on spinal reflexes of the cat

Abstract

The effect of arecoline on a monosynaptic reflex from the lumbar spinal cord was studied in acute low-spinal cats anesthetised with chloralose. Drugs were injected intraarterially into the spinal cord blood supply and afferent influence was further minimized by sectioning dorsal roots. Arecoline hydrobromide and oxotremorine depressed both monosynaptic and polysnaptic reflex discharges recorded from the ventral root when the corresponding dorsal root was stimulated. The depression was slower in onset and longer in duration when compared to that resulting from nicotine hydrochloride. The depression of spinal reflexes by arecoline was blocked by i.v. atropine sulfate, only slightly antagonized by i.v. atropine methyl nitrate and was unaffected by i.v. methantheline bromide. Mecamylamine hydrochloride (i.v.) completely blocked the depression of reflexes by nicotine but had no effect on the arecoline-induced reflex depression. This depressant effect of arecoline is probably due to stimulation of muscarinic receptors on the inhibitory Renshaw cells.