ACUTE UP-REGULATION OF THE RAT BRAIN SOMATOSTATIN RECEPTOR-EFFECTOR SYSTEM BY LEPTIN IS RELATED TO ACTIVATION OF INSULIN SIGNALING AND MAY COUNTERACT CENTRAL LEPTIN ACTIONS

摘要

Leptin and somatostatin (SRIF) have opposite effects on food seeking and ingestive behaviors, functions partially regulated by the frontoparietal cortex and hippocampus. Although it is known that the acute suppression of food intake mediated by leptin decreases with time, the counter-regulatory mechanisms remain unclear. Our aims were to analyze the effect of acute central leptin infusion on the SRIF receptor-effector system in these areas and the implication of related intracellular signaling mechanisms in this response. We studied 20 adult male Wister rats including controls and those treated intracerebroventricu-larly with a single dose of 5 fig of leptin and sacrificed 1 or 6 h later. Density of SRIF receptors was unchanged at 1 h, whereas leptin increased the density of SRIF receptors at 6 h, which was correlated with an elevated capacity of SRIF to inhibit forskolin-stimulated adenylyl cyclase activity in both areas. The functional capacity of SRIF receptors was unaltered as cell membrane levels of alphai1 and alphai2 subunits of G inhibitory proteins were unaffected in both brain areas.