Differential effects of sulfated cholecystokinin octapeptide and proglumide injected intrathecally on antinociception induced by beta-endorphin and morphine administered intracerebroventricularly in mice.
The effects of sulfated cholecystokinin octapeptide (CCK-8s) and CCK-8s antagonist, proglumide, given intrathecally (i.t.) on inhibition of the tail-flick and hot-plate paw-licking responses induced by beta-endorphin and morphine given intracerebroventricularly (i.c.v.) were studied in male ICR mice. Both CCK-8s (up to 0.5 ng) and proglumide (up to 10 micrograms) injected alone did not affect significantly the control latencies of the tail-flick and paw-licking responses. I.t. injection of CCK-8s as doses from 0.125 to 0.5 ng dose dependently attenuated inhibition of the tail-flick response induced by i.c.v. administered beta-endorphin. The antagonistic effect of CCK-8s on beta-endorphin-induced inhibition was blocked by the co-i.t. injection of proglumide (0.1-1 micrograms) in a dose-dependent manner. High doses (2.5-10 micrograms) of proglumide given i.t. dose dependently enhanced inhibition of the tail-flick response induced by i.c.v. administered beta-endorphin. However, i.t. injection of CCK-8s and proglumide did not affect inhibition of the paw-licking response induced by i.c.v. administered beta-endorphin. The inhibitions of the tail-flick and paw-licking responses induced by i.c.v. administered morphine were not affected by i.t. injection of CCK-8s or proglumide. Our results suggest that CCK-8s in the spinal cord may play an important modulatory role in attenuating the descending pain inhibition induced by i.c.v. administered beta-endorphin but not morphine.
Suh
H H
HH
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226.
Tseng
L F
LF
D000700:Analgesics; D000818:Animals; D005973:Glutamine / Q000031:analogs & derivatives*; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011377:Proglumide / Q000008:administration & dosage / Q000494:pharmacology*; D011930:Reaction Time; D012844:Sincalide / Q000008:administration & dosage / Q000494:pharmacology*; D001615:beta-Endorphin / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D000700:Analgesics; D005973:Glutamine; D001615:beta-Endorphin; D009020:Morphine; D011377:Proglumide; D012844:Sincalide