Effects of central monoamine compounds on tranylcypromine-induced barbital-withdrawal convulsions

Challenge with tranylcypromine (Tcp) during barbital (B) withdrawal induces doserelated clonic-tonic convulsion (C-TC), which is also related to the severity of withdrawal signs and their changes with the passage of time. The effects of neuropharmacological agents on the Tcp-induced convulsions were observed. dl-Propranolol, phentolamine, phenoxybenzamine and methysergide had been administered intraperitoneally 20≈30 minutes before Tcp challenge. B-withdrawn rats had been pretreated with α-methyl-p-tyrosine, 5-hydroxytryptophan, p-chlorophenylalanine or reserpine, or with the combination of iproniazid and reserpine (5 hrs after iproniazid administration) before Tcp challenge. α-MT and dl-propranolol inhibited B withdrawal convulsion markedly, though high doses of dl-propranolol rather tended to show a less inhibitory effect on the convulsion. α-Adrenoceptor blockers scarely inhibited the convulsion. Methysergide or 5-HTP failed to inhibit, but PCPA intensified the convulsion. Reserpine, when administered alone, aggravated the convulsion, but when administered after iproniazid, inhibited it significantly. These findings suggested that the balance between the activities of noradrenergic and serotonergic neurons might be of importance in the manifestation of B withdrawal convulsions, the former probably being excitatory and the latter, inhibitory.