Effects of acute and chronic desipramine treatment on somatostatin receptors in brain.

The effects of acute (5 mg/kg, IP twice daily for 2 days) and chronic (5 mg/kg IP twice daily for 21 days) administration of desipramine (DMI) on [125I]-Tyr11-somatostatin binding sites in brain were examined. There was no change in [125I]Tyr11-somatostatin binding in membranes prepared from the frontal cortex, striatum, and hippocampus of rats acutely or chronically treated with DMI as compared to non treated animals. [125I]Tyr11-somatostatin binding was increased in membranes prepared from the rat nucleus accumbens only after chronic DMI administration. Scatchard analysis of the binding data from the nucleus accumbens showed that [125I]Tyr11-somatostatin labels a single population of somatostatin binding sites with an affinity constant, Kd, of 1.8 +/- 0.60 nM and a Bmax of 330 +/- 90 fmol/mg protein. Chronic treatment with DMI increased the Bmax (500 +/- 140 fmol/mg protein) but had no effect on the Kd. This finding shows a regional effect of DMI on [125I]Tyr11-somatostatin binding sites in rat brain and suggests that somatostatin may play a role in the pathophysiology of depression.