NEONATAL DESIPRAMINE TREATMENT ALTERS FREE-RUNNING CIRCADIAN DRINKINGRHYTHMS IN RATS

Neonatal treatment with monoamine reuptake inhibitors results in a con stellation of neurobehavioral alterations in adult rats that may model human depression. Since alterations in circadian rhythmicity have bee n reported in both depressed patients and in animal depression models, the present study examined the effects of neonatal desipramine treatm ent (5.0 mg/kg SC from postnatal day 7 through 22) on free-running cir cadian drinking rhythms. Rhythmicity was examined in constant darkness (DD), constant light (LL), and during adult desipramine treatment (0. 25 mg/ml via the drinking water). Compared with saline-treated control s, neonatal desipramine lengthened free-running period in DD, blunted the period-altering effect of LL, and potentiated the period-altering effect of adult desipramine treatment. Neonatal desipramine treatment also increased circadian amplitude and spectral magnitude, but did not modify the effects of light or adult desipramine on these parameters. These results provide further evidence that behavioral depression is associated with alterations in circadian rhythmicity, and are consiste nt with the hypothesis that such relationships are mediated by brain m onoaminergic systems.