On the presence of receptors for ACTH neuropeptides in the brain

There is considerable evidence, based on a variety of CNS effects and structure-activity relations as well as on indirect receptor studies, for the presence of multiple binding sites for ACTH neuropeptides in the CNS. Mainly because of the very low effective CNS concentrations of these peptides, putative CNS receptors seem characterized by very high affinity and very low capacity. These properties interfere with the demonstration of such receptor sites by direct binding assays using 3H-peptides and seem to necessitate the use of labeled neuropeptides with considerably higher specific activities.