Investigations on α-MSH and MIF-I effects on cyclic AMP levels in rat brain

Abstract

It has beensuggested that the peptides alpha-melanocyte stimulating hormone (α-MSH) and MSH-release inhibitory factor (MIF-I) may alter adenosine-3′, 5′-cyclic monophosphate (cAMP) metabolism [13,26]. Normal and hypophysectomized (hypoxed) rats were administered saline (controls IP daily × 3), α-MSH (80 μg/kg IP daily × 3) or MIF-I (1 or 10 mg/kg IP daily × 3) and sacrificed 30 min after the third injection in a focused microwave oven (1.5 KW; 2–3 sec). Various brain areas were then assayed for cAMP levels after each treatment. The occipital cortex area was the only area to show consistent changes in both normal and hypoxed rats after α-MSH treatment. These findings were replicated for the occipital cortex in a second group of normal and hypoxed rats which were similarly treated. The results suggest a correlation between the rise in cAMP found and reported changes in visual acuity and attention in rats and humans after treatment with α-MSH [8, 14, 23].