Nitric oxide: a gas as a modulator of neuroendocrine secretions.

Nitric oxide (NO), previously identified with endothelium derived relaxing factor (EDRF), is thought to play a role in central neurotransmission: it is characterized by high lipid solubility and short half life, and NO-synthase, the enzyme which generates NO from L-arginine, has been found in the central nervous system (CNS), both in neuronal and glial cells. NO is believed to be involved in many neural events, such as neurotoxicity from N-methyl-D-aspartate (NMDA) receptor overstimulation, brain damage from vascular stroke, fever, nociception, memory and appetite control. Recent evidence implicates NO as a modulator of endocrine secretions, with inhibition of insulin, growth hormone (GH) and oxytocin release and stimulation of vasopressin (AVP), adrenocorticotropin (ACTH) and corticotropin releasing hormone (CRH) release. NO and prostaglandins could mediate neuroendocrine activities of cytokines such as interleukin-1 (IL-1) and interleukin-2 (IL-2), particularly in the CNS.