Effects of chronic desipramine on waiting behaviour for a food reward in olfactory bulbectomized rats

The effects of olfactory bulbectomy (OB) on the 'waiting behaviour' of rats for a food reward in a T-maze, as well as the effect of chronic treatment with desipramine (7.5 mg/kg, i.p. x 14 days) prior to and throughout testing was assessed. In the T-maze, the time spent in locating a reward was longer in OB rats during the first phase of the food reward test. However, all groups chose the larger reward in at least 80% of trials by day 5 of test. Upon imposition of a delay in acquisition of the larger reward (phase 2), sham-operated rats chose the larger reward in correspondingly fewer trials until, by day 5, only 13% (control sham group) and 29% (desipramine-treated sham group) of trials were for the larger but delayed reward. By contrast, both OB rat groups continued to choose the larger but delayed reward throughout phase 2 in the majority of trials. The typical behavioural hyperactivity of OB rats in the 'open field' apparatus was attenuated by chronic administration of DMI. The results suggest that the OB rat has a deficit in food-motivated behaviour and appears to have reduced adaptation of this learned response when the conditions of the test are altered. Chronic desipramine treatment did not attenuate this effect.