The Prolonged Anticonvulsant Action of Taurine on Genetically Determined Seizure-Susceptibility

Abstract

A prolonged anticonvulsant action of taurine has been shown in a strain of seizure susceptible rats. The audiogenic rat (AS) has lower intracerebral electroshock thresholds in three auditory nuclei; the ventral cochlear, the inferior colliculi and the medial geniculate, and in one nonauditory structure; the reticular formation, than a strain of nonaudiogenic rats (NAS). Furthermore, the AS animals routinely display maximal (tonic-clonic) convulsion, regardless of brain structure stimulated, whereas NAS subjects respond with minimal (clonic) convulsions. Within three minutes of intraventricular injection of 8 μ moles, taurine reduces the susceptibility of AS rats to intracerebral electroshock seizures along with attenuation of the severity of the convulsion. The initial elevation in intracerebral electroshock threshold returns to pretreatment value at 24 hours, only to rise again at 48 hours and to remain elevated through day six after injection. In contrast, the severity of convulsions remains attenuated through 24 hours, after which it returns to pre-injection level. By comparison, NAS animals injected intracerebroventricularly in an identical fashion to the AS rats showed no changes in either seizure threshold or severity of convulsion. The direct injection of 200n-moles of taurine in the inferior colliculi of AS rats produced a slow developing, but prolonged, elevation of intracerebral electroshock threshold of this auditory nuclei. However, at no time after the intracerebral injection of taurine was convulsive severity changed. Injection of taurine into the inferior colliculi of NAS subjects did not change either susceptibility or severity of intracerebral electroshock seizures. The data indicate that taurine produces an anticonvulsant effect which is slow in onset, potent, selective and prolonged.