Epileptogenic activity induced by histamine H₁ antagonists in amygdala-kindled rats

The epileptogenic activities induced by histamine H₁ antagonists in amygdala-kindled rats were studied in comparison with activities in nonkindled rats (sham rats). Intraperitoneal injection of pyrilamine, diphenhydramine and ketotifen resulted in behavioral and electroencephalogram (EEG)-detected seizures in amygdala-kindled rats at doses which caused no or negligible seizures in sham rats. On the other hand, loratadine and cetirizine caused no behavioral or EEG seizures in either amygdala-kindled or sham rats even at a dose of 40 mg/kg. In conclusion, first-generation H₁ antagonists likely elicit epileptogenic activity in amygdala-kindled rats more potent than that in sham rats.