Tizanidine Protects Mice against Convulsions Induced by Lidocaine: Involvement of α2-Adrenoceptors

Abstract: The effects of α-adrenoceptors agents on seizures induced by intraperitoneal administration of lidocaine (75 mg/kg) were studied in mice. Pretreatment with the selective α₂-adrenoceptor agonist, tizanidine, decreased the incidence of seizures induced by lidocaine. Tizanidine increased the latency to the first seizure in those animals which progressed to seizures. The blockade of α₂-adrenoceptors with yohimbine or phentolamine counteracted the protection induced by tizanidine. The seletive α₂-adrenoceptor antagonist, prazosin, did not modify the protection induced by tizanidine. The α₂-adrenoceptor agonist clonidine also increased the latency to the first seizure induced by lidocaine. The protective effect of clonidine was also reversed by pretreatment with the selective α₂-adrenoceptor antagonist yohimbine. Taken together, these results suggest that α₂-adrenoceptors are involved in seizures induced by lidocaine.