Role of 5-Hydroxytryptamine in the Regulation of Brain Neuropeptides in Normal and Diabetic Rat

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Abstract
The effect of 5-hydroxytryptamine (5-HT) alteration on brain dopamine (DA), norepinephrine (NE), .beta.-endorphin (.beta.E) and immunoreactive insulin (IRI) was studied in Sprague-Dawley diabetic and control rats. Diabetics was induced using alloxan (45 mg/kg), 15 days prior to sacrificing. Both control and diabetic animals were treated with either p-chlorophenylalanine (PCPA, 300 mg/kg) 3 days prior to sacrificing or floxetine (10 mg/kg) twice daily for 3 days. PCPA treatment significantly decreased brain content of 5-HT and 5-hydroxyindole acetic acid (5-HIAA) while it caused significant increase and decrease in brain .beta.E and insulin levels, respectively, in both normal and diabetic rat. Meanwhile, the administration of fluoxetine resulted in significant increase in brain content of 5-HT, DA, NE and insulin but significant decline of .beta.E in diabetic and saline control rats. The results of this experiment indicate that 5-HT may be regulating both .beta.E and insulin regardless of the availability of pancreatic insulin.