Comparison of the effects of sibutramine and other monoamine reuptake inhibitors on food intake in the rat

1. The effects of the potent 5-hydroxytryptamine (5-HT) and noradrenaline reuptake inhibitor (serotonin-noradrenaline reuptake inhibitor, SNRI), sibutramine, on the cumulative food intake of freely-feeding male Sprague-Dawley rats during an 8 h dark period were investigated and compared to those of the selective 5-HT reuptake inhibitor (selective serotonin reuptake inhibitor, SSRI), fluoxetine; the selective noradrenaline reuptake inhibitor, nisoxetine; the 5-HT and noradrenaline reuptake inhibitors, venlafaxine and duloxetine; and the 5-HT releaser and 5-HT reuptake inhibitor, (+)-fenfluramine.
2. Sibutramine (3 and 10 mg kg⁻¹, p.o.) and (+)-fenfluramine (1 and 3 mg kg⁻¹, p.o.) produced a significant, dose-dependent decrease in food intake over the 8 h dark period. These responses became apparent within the first 2 h following drug administration.
3. Fluoxetine (3, 10 and 30 mg kg⁻¹, p.o.), and nisoxetine (3, 10 and 30 mg kg⁻¹, p.o.) had no significant effect on food intake during the 8 h dark period. However, a combination of fluoxetine and nisoxetine (30 mg kg⁻¹, p.o., of each) significantly decreased food intake 2 and 8 h after drug administration.
4. Venlafaxine (100 and 300 mg kg⁻¹, p.o.) and duloxetine (30 mg kg⁻¹, p.o.) also significantly decreased food intake in the 2 and 8 h following drug administration.
5. The results of this study demonstrate that inhibition of 5-HT and noradrenaline reuptake by sibutramine, venlafaxine, duloxetine, or by a combination of fluoxetine and nisoxetine, markedly reduces food intake in freely-feeding rats and suggest that this may be a novel approach for the treatment of obesity.