© 1986 by The Society for Integrative and Comparative Biology
Multi-Independent Actions of Peptides in the Brain: LHRH, MIF-1 and CRF1
Veterans Administration Medical Center and Tulane University School of Medicine New Orleans, Louisiana 70146
SYNOPSIS. The effects on the central nervous system of four hypothalamic peptides, luteinizing hormone-releasing hormone (LHRH), melanocyte stimulating hormone releaseinhibiting factor-1 (MIF-1), the structurally related Tyr-MIF-1, and corticotropin releasing factor (CRF) are reviewed. Attention is focused on those functions, particularly behavioral actions, that are not dependent upon the pituitary effects of the peptide. For LHRH, growing evidence indicates that thestructural requirements that are important for its behavioral effects are different from those essential for gonadotropin release. Actions of LHRH analogs at the pituitary often do not correlate with the behavioral effects and C-terminal fragments that are inactive at the pituitary can facilitate lordosis. The same portion of the decapeptide shows species differences in the naturally occurring form of the molecule, raising the possibility that these structural differences could be behaviorally relevant. MIF-1 appears to exert many of its effects on the CNS by antagonizing the effects of opiate substances or by potentiating the effects of dopamine. Neither of these actions appears to involve classical agonist- or antagonist-like binding to the opiate or dopamine receptor, but MIF-1 can increase the affinity of agonist binding to the dopamine receptor. Tyr-MIF-1, like MIF-1, can antagonize some opiate-induced effects but differs from MIF-1 in other tests including in vitro binding. CRF shows several behavioral effects that are independent of its ability to release the pituitary hormones ACTH, beta endorphin and MSH or are different from the effects seen after administration of those hormones.