OBSERVATIONS ON CHLORALOSE‐INDUCED MYOCLONUS IN GUINEA‐PIGS

Abstract

The physiological, biochemical and pharmacological features of α‐chloralose‐induced myoclonus in the guinea‐pig have been studied. EMG bursts in muscles jerking in chloralose‐induced myoclonus are long, and are not time‐locked to any cortical event recorded in the EEG, although they are evoked by auditory or peripheral nerve stimuli. The efferent conduction velocity down the spinal cord of the signals generating the EMG bursts is fast but the afferent conduction velocity up the cord for stimulus‐evoked jerks is slow, in distinction to the reverse characteristics of the spino‐bulbo‐spinal reflex arc. α‐Choralose did not cause any consistent change in 5‐hydroxytryptamine (5‐HT) or 5‐hydroxy‐indoleacetic acid levels in any brain area, nor did it alter 5‐HT turnover as judged by the depletion of 5‐HT after p‐chlorophenylalanine pretreatment. Pretreatment of animals with drugs that increase brain 5‐HT action (l‐tryptophan with a monoamine oxidase inhibitor, or 5‐hydroxytryptophan), or antagonize the action of 5‐HT (cyproheptadine) did not abolish or obviously increase chloralose‐induced myoclonus. Chloralose‐induced myoclonus is not similar to 5‐HT‐sensitive reticular reflex myoclonus in man. 1980 British Pharmacological Society