AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 6 901-R907, Copyright © 1988 by American Physiological Society
Behavioral evidence for cholecystokinin-opiate interactions in neonatal rats
A. Weller and E. M. Blass
Department of Psychology, Johns Hopkins University, Baltimore, Maryland 21218.
In adult mammals, cholecystokinin (CCK)-opiate interactions are complex and
task dependent. Specifically, CCK antagonizes opiate effects in some cases,
yet acts similarly to opiate agonists in others. The present study used
behavioral measures to determine how CCK interacts with opiates in neonatal
rats. CCK, at doses of 1 microgram/kg and higher, markedly reduced
isolation-induced distress vocalization in rat pups. Moreover, CCK
selectively prevented naltrexone antagonism of opiate-mediated reduction in
distress vocalization in 3- and 11-day-old rats. Yet CCK did not affect
opiate-induced analgesia, as measured by the hot-plate paw-lift response.
Thus CCK either did not interact with opiates or did so agonistically, with
the same (low) dose range, and within subjects. These findings suggest
independence of stress and pain systems in neonatal rats and demonstrate a
functional interaction between CCK and opioid systems.
