A COMPARISON OF THE ACUTE EFFECTS OF A TRICYCLIC AND A MAOI ANTIDEPRESSANT ON SEPTAL DRIVING OF HIPPOCAMPAL RHYTHMICAL SLOW ACTIVITY

In free-moving male rats, the function relating frequency to the thres hold current required to drive hippocampal rhythmical slow activity (R SA) with septal stimulation has a minimum at 130ms. Both classical anx iolytics (e.g. benzodiazepines) and the novel anxiolytic buspirone sho w similar effects on septal driving of RSA. The tricyclic antidepressa nt imipramine may be as effective as anxiolytic drugs in treatment of generalized anxiety disorder. The antidepressant monoamine oxidase inh ibitor phenelzine has also been reported to be effective in treating a nxiety, but this may reflect an action on ''atypical depression'' rath er than ''anxiety''. The present study therefore compared the effects of acute administration of imipramine and phenelzine on septal driving of RSA to determine whether either would mimic anxiolytics in this te st. Rats were chronically implanted with septal stimulating electrodes and subicular recording electrodes. Three groups of rats received IP injection of either imipramine (5.9-13.3 mg/kg or 13.3-30 mg/kg) or ph enelzine (0.2-5.4 mg/kg). The effects produced by imipramine were very similar to the effects produced by anxiolytic drugs. In contrast, the effects produced by phenelzine were essentially opposite to those of both anxiolytic drugs and imipramine. The present experiment suggests that imipramine may act as a true anxiolytic, in addition to its conve ntional antidepressant properties. In contrast, phenelzine may be effe ctive in cases where the etiology is essentially that of depression ev en when the symptomatology appears to be that of anxiety.