Meal-induced c-fos expression in brain stem is not dependent on cholecystokinin release.
Sprague-Dawley rats injected with a "physiological" dose of cholecystokinin octapeptide (CCK-8; 6 micrograms/kg ip) expressed c-fos immunoreactivity in the nucleus of the tractus solitarius (NTS) and the area postrema (AP) of the brain stem. Injection of the CCK-A antagonist L-364,718 30 min before CCK-8 injection eliminated c-fos expression in these regions. These findings support the hypothesis that CCK-8 induced c-fos expression is mediated by CCK-A receptors. We then tested whether a meal (Isocal) could activate c-fos, and, if so, whether this response could be eliminated by L-364,718. Ingestion of Isocal induced c-fos immunoreactivity in the NTS and AP. Meal-induced c-fos expression was not blocked by the CCK-A antagonist L-364,718. These findings demonstrate for the first time that a purely physiological nonnoxious stimulus, a meal, induces c-fos in the rat brain stem and indicate that feeding induces c-fos expression by a pathway that is largely, if not entirely, independent of CCK release.
Fraser
K A
KA
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Davison
J S
JS
D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology; D001933:Brain Stem / Q000378:metabolism*; D002766:Cholecystokinin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020109:Devazepide; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004435:Eating; D008526:Medulla Oblongata / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000494:pharmacology
D001570:Benzodiazepinones; D016760:Proto-Oncogene Proteins c-fos; D002766:Cholecystokinin; D020109:Devazepide; D012844:Sincalide; D004121:Dimethyl Sulfoxide