Histaminergic mechanisms in experimental convulsions.

ABSTRACT

Effect of some histamine (HA) agonists and antagonists were assessed on electroshock (MES) convulsions in mice and rats. In mice, pretreatment with the HA precursor, l-histidine (100, 500 and 1000 mg/kg) precipitated seizures after a subthreshold (30 mA) stimulus. Both incidence (%) and tonic hind limb extensor phase (THE) were more than that in vehicle treated controls. The H1 blockers, pheniramine (25 mg/kg) and promethazine (25 mg/kg) both protected against (60 mA) MES and both incidence of convulsions and THE were reduced. A similar protective effect was not seen with either the H2 blocker, cimetidine (up to 200 mg/kg), or atropine (1 mg/kg). In rats, both the classical antihistamines blocked MES seizures, whereas, the H2-blocker, cimetidine, and atropine were, ineffective. Further, both H1 blockers were ineffective in antagonizing seizures induced by pentylenetetrazole, INH, caffeine or strychnine. These results are discussed in light of a possible HA-ergic regulation of experimental convulsions.