A Modulatory Effect of Pituitary Polypeptides on Peripheral Nerve and Muscle

Abstract

Publisher Summary This chapter discusses the modulatory effect of pituitary polypeptides on peripheral nerve and muscle. Pituitary polypeptides are implicated in many ways in the modulation of nervous activity. The implantation of ACTH 4-10, in various brain regions indicates that it exerts its effects within the nervous system. Studies on peripheral nerve and skeletal muscle also indicate an extradrenal effect of pituitary polypeptides, an action that may involve the neuromuscular junction. In these experiments, adult male rats weighing from 200 to 300 g were maintained on a 12 hr dark-12 hr light schedule. α-MSH, β-MSH, ACTH 4-10 ,-7-L-phe and its D-isomer were administered to normal and hypophysectomized rats. These are all pituitary polypeptides, sharing a common amino acid sequence and without adrenocortical stimulating action. ACTH 4-10 ,-7-L-phe and α-MSH increase the amplitude of sciatic nerve and gastrocnemius muscle action potentials (APs) and decrease fatigue, when measured in situ during 30 min of nerve stimulation. The augmenting action of these polypeptides on AP amplitude is most clearly seen in fatigued animals and particularly in the hypophysectomized, fatigued rat.