Effects of acute and chronic imipramine administration on conflict behavior in the rat: a potential "animal model" for the study of panic disorder?

Although numerous animal procedures have been employed in the study of generalized anxiety and agents effective in treating generalized anxiety, an analogous "behavioral model" for the study of panic disorder does not exist. In the present study, the effects of imipramine were examined in a potential "animal model" for panic disorder, the conditioned suppression of drinking (CSD) paradigm. In daily 10-min sessions, water-deprived rats were trained to drink from a tube that was occasionally electrified (0.5 mA). Electrification was signalled by a tone. Imipramine was administered both in an acute (3.5-20 mg/kg, IP) and a chronic (2.5 mg/kg, IP, twice daily for 5 weeks) regimen. Acute administration of imipramine resulted in a decrease in the number of shocks accepted and a decrease in water intake. In contrast, chronic administration of imipramine resulted in a gradual increase in the number of shocks received in CSD sessions over the course of several weeks of testing. This time-dependent increase in punished responding in the CSD observed during chronic imipramine treatment parallels the time-dependent reduction in the severity and frequency of panic attacks in panic disorder patients receiving chronic imipramine. Thus, the CSD paradigm might serve as an "animal model" for the study of panic disorder and potential anti-panic agents.