Effects of selective serotonin reuptake inhibitors on immobility time in the tail suspension test in streptozotocin-induced diabetic mice.

We examined the effects of fluoxetine and fluvoxamine, selective serotonin reuptake inhibitors (SSRIs), and desipramine, a selective noradrenaline (NA) reuptake inhibitor, given alone or in combination with diazepam on immobility time in the tail suspension test in diabetic mice. Immobility time was significantly longer in diabetic than in nondiabetic mice. Diazepam (0.1 and 0.3 mg/kg s.c.) dose-dependently decreased immobility time in diabetic mice to the level observed in saline-treated nondiabetic mice. However, diazepam had no significant effect on immobility time in nondiabetic mice. Fluoxetine (3-56 mg/kg i.p.) and desipramine (1-30 mg/kg i.p.) produced marked, dose-dependent suppression of immobility time in both nondiabetic and diabetic mice. However, anti-immobility effects of fluoxetine and desipramine in diabetic mice were less than those in nondiabetic mice. Fluvoxamine (3-30 mg/kg i.p.) produced a dose-dependent suppression of immobility time in nondiabetic mice but not in diabetic mice. The anti-immobility effects of fluoxetine, fluvoxamine and desipramine in nondiabetic mice were antagonized by pretreatment with diazepam (0.3 mg/kg s.c.). Furthermore, fluoxetine, fluvoxamine and desipramine had no effect on the immobility time in diazepam (0.3 mg/kg s.c.)-treated diabetic mice. These results indicate that the anti-immobility effects of SSRIs and desipramine are less in diabetic mice than in nondiabetic mice in the tail suspension test. Furthermore, in diabetic mice, SSRIs and selective NA reuptake inhibitors did not affect immobility time even though the prolonged duration of immobility was suppressed by pretreatment with diazepam.