Convulsions induced by methyl beta-carboline-3-carboxylate in mice: effects of preceding saline injections.

The convulsant effects of a high (5 mg/kg intraperitoneally, i.p.) dose of benzodiazepine (BZD) receptor ligand methyl beta-carboline-3-carboxylate (beta-CCM), whether or not preceded by administration of two lower doses of beta-CCM (0.5 and 1 mg/kg i.p.) or of saline were studied in nine inbred mouse strains. In five of the strains (A/J, BALB/cBy, C3H/HeJ, CBA/H, and DBA/2J), neither saline nor preceding injections of beta-CCM had any effect on subsequent reactivity to the subsequent convulsant dose. In the other 4 strains, such injections induced either tolerance (CPB-K, NZB), or sensitization (C57BL/6J, XLII), whatever the compound subsequently administered (beta-CCM or saline). In these strains, the data rule out any tolerance or sensitization effect due to beta-CCM, but suggest that such effects could be due to injection itself.