ICV-CRH potently affects behavior without altering antinociceptive responding.
To explore the hypothesized integrative function of corticotropin releasing hormone (CRH) in the stress response, stress-related behaviors including antinociception were studied in rats after either intracerebroventricular (ICV) or peripheral administration of CRH. The effects of low-dose (0.3 microgram) and high-dose (3.0 micrograms) ICV-CRH were compared to those of vehicle, employing a within-S design. The two doses yielded comparable behavioral changes suggestive of increased arousal and stress. These changes were characterized by significant increases in grooming, walking, burrowing, self-gnawing, and pica, and decreases in rearing and sleeping. None of these effects of ICV-CRH were obtained with peripheral administration of the same doses. The hot-plate test of analgesia failed to show a significant effect of ICV-CRH or peripherally administered CRH. A between-S experiment incorporating both the tail-flick and the hot-plate tests of analgesia compared ICV-CRH (3.0 micrograms) with vehicle. ICV-CRH did not affect antinociceptive responding in either of these tests. In contrast, ICV morphine (10 micrograms) yielded potent analgesia in both tests. Thus, with doses of ICV-CRH yielding clear evidence of stress-related behavior, no evidence of analgesia was obtained. These findings question the possible role of central CRH systems in antinociceptive processes.
D000698:Analgesia; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002552:Cerebral Ventricles; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008297:Male; D009020:Morphine; D010146:Pain; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000139:chemically induced
D009020:Morphine; D003346:Corticotropin-Releasing Hormone