DEFICIT OF INHIBITORY GLYCINE RECEPTORS IN SPINAL-CORD FROM PERUVIAN PASOS - EVIDENCE FOR AN EQUINE FORM OF INHERITED MYOCLONUS

Inherited myoclonus in Poll Hereford calves and spasticity in the spas tic mouse (spa/spa) are characterized by myoclonic jerks of the skelet al musculature which occur spontaneously and in response to sensory st imuli, symptoms resembling those in subconvulsive strychnine poisoning . The primary, biochemical defect in these myoclonic animals is a defi cit of inhibitory glycine receptors in the central nervous system. We now report the occurrence of similar stimulus-induced myoclonus in ind ividual, pure-bred Peruvian Paso horses and an associated, specific de ficiency in the density of [H-3]strychnine binding to inhibitory glyci ne receptors sites in spinal cord of these animals. Specificity of the deficit was confirmed by a demonstrated lack of change in the density of several other receptor types in affected spinal cord, including mu scarinic receptors and GABA(A)/benzodiazepine receptors. In light of t he existence of genetically-inherited myoclonus in other species, thes e results suggest the occurrence of an equine form of the disorder.