Cholecystokinin-induced antinociception is not blocked by CCK-A or CCK-B receptor antagonists

Heterodimerization of Type A and B Cholecystokinin Receptors Enhance Signaling and Promote Cell Growth

Dimerization of several G protein-coupled receptors has recently been described, but little is known about its clinical and functional relevance. Cholecystokinin (CCK) and gastrin are structurally related gastrointestinal and neuronal peptides whose functions are mediated by two structurally related receptors in this superfamily, the type A and B CCK receptors. We previously demonstrated spontaneous homodimerization of type A CCK receptors and the dissociation of those complexes by agonist occupation (Cheng, Z. J., and Miller, L. J. (2001) J. Biol. Chem. 276, 48040-48047). Here, for the first time, we also demonstrate spontaneous homodimerization of type B CCK receptors, as well as heterodimerization of that receptor with the type A CCK receptor. Unlike type A CCK receptor dimers, the homodimerization of type B CCK receptors was not affected by ligand occupation. However, although heterodimers of type A and B CCK receptors bound natural agonists normally, they exhibited unusual functional and regulatory characteristics. Such complexes demonstrated enhanced agonist-stimulated cellular signaling and delayed agonist-induced receptor internalization. As a likely consequence, agonist-stimulated cell growth was markedly enhanced in cells simultaneously expressing both of these receptors. Our results provide the first evidence that heterodimerization of G protein-coupled receptors can form a more "powerful" signaling unit, which has potential clinical significance in promoting cell growth.

Spatial memory deficit and emotional abnormality in OLETF rats

Cholecystokinin (CCK) is deeply involved in the control of learning and emotional behaviors. The authors characterize the behavioral properties of Otsuka Long Evans Tokushima Fatty (OLETF) rats, which lack the CCK-A receptor because of a genetic abnormality. In the Morris water-maze task, the OLETF rats showed an impaired spatial memory. In the inhibitory avoidance test, they showed facilitating response 24 h after training. Hypoalgesia was observed in a hot-plate test. In the elevated plus-maze and food neophobia test, OLETF rats showed an anxiety-like response. In addition, OLETF rats were hypoactive in the Morris water-maze and the elevated plus-maze. The results suggest that the OLETF rats showed a spatial memory deficit, hypoactivity and anxiety due, at least in part, to the lack of CCK-A receptors.

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Cholecystokinin-8-like-immunoreactive fibers in rat lumbosacral autonomic regions are sexually dimorphic and altered by a reduction of androgen receptors

Cholecystokinin-8-like-immunoreactive (CCK-8-LI) fibers in laminae VII and X of the rat lumbosacral spinal cord demarcate the position of preganglionic autonomic neurons. This investigation reveals that adult male Sprague-Dawley, or King-Holtzman/Sprague-Dawley rats contain more CCK-8-LI fibers in lumbosacral laminae VII and X than adult females. Furthermore, testicular feminization mutation male rats (which lack 85-90% of their functional androgen receptors) contain fewer CCK-8-LI fibers than normal male or female rats, with the amount of CCK-8-LI being reduced to a greater extent in the sympathetic vs. the parasympathetic regions of the lumbosacral spinal cord. Thus, CCK-8-LI in testicular feminization mutation male rats has a distinctly female-like pattern. These results suggest that testosterone is a regulatory factor for CCK-8-LI fibers found in laminae VII and X of the lumbosacral spinal cord. Sexual dimorphism in lumbosacral CCK-8-LI fibers may contribute to modulating the final common pathway which differentially regulates the reproductive organs and stereotypic reproductive behavior, and may be involved with the sex differences described for pain.

Effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides from 1994 through 1998

Effects of peptides on the central nervous system are presented in two ways so as to provide a cross-listing. In the first table, the peptides are listed alphabetically. In the second table, the central nervous system effects are arranged alphabetically. No longer can there be any doubt that peptides affect the central nervous system, sometimes in several ways.