Chronic treatment with imipramine does not reverse the effects of 3 anxiogenic compounds in a test of anxiety in the rat

The ability of chronic treatment with imipramine (an antidepressant with anti-panic activity) to antagonise the anxiogenic effects of 3 different compounds was investigated in the elevated plus-maze. The compounds chosen are likely to produce anxiety by activity at different sites in the central nervous system: yohimbine, by blocking the alpha 2-adrenoceptor; FG 7142, by action at the beta-carboline site on the GABA-benzodiazepine receptor complex and pentylenetetrazole, by acting at the picrotoxinin site on this complex. Administration of imipramine following 21 days pre-treatment did not produce a significant consistent anxiolytic effect alone and was unable to reverse the anxiety produced by any of the 3 anxiogenic compounds. Our results are discussed in terms of the nature of the anxiety produced by the anxiogenic drugs and the sensitivity of tests of anxiety to anti-panic agents.