Comparison of the effects of two 'sleep' peptides, delta sleep-inducing peptide and arginine-vasotocin, on single neurons in the rat and rabbit brain stem.

The effects of delta sleep-inducing peptide and arginine-vasotocin were assessed on single neurons in the nucleus reticularis gigantocellularis of the brain stem in rats and rabbits. Both peptides showed predominantly excitatory actions in both species when applied by microiontophoresis. A small proportion of cells was inhibited by delta sleep-inducing peptide in the rat. Responses to delta sleep-inducing peptide were short-lasting, dose-dependent and showed no significant desensitization to repeated applications. Responses to arginine-vasotocin were of very long time course and showed profound desensitization. No statistically significant correlation was seen between cells responsive to delta sleep-inducing peptide and those responsive to arginine-vasotocin. We conclude that both 'sleep' peptides have similar actions on central neurons and that they are active in both rats and rabbits. However, no evidence was found to suggest a common mechanism of action for both substances.