Effects of paraventricular nucleus injection of CCK-8 on plasma CCK-8 levels in rats.
The aim of the study was to determine whether paraventricular nucleus (PVN) injection of an anorexic 500-pmol dose of cholecystokinin (CCK)-8 could increase plasma CCK-8 levels sufficiently to suppress feeding by a peripheral mechanism. Rats received PVN injections of CCK-8 either alone or with 3H-labelled propionylated CCK-8 (3H-pCCK-8) and plasma samples were taken at various times from 3 to 120 min post-injection. Plasma CCK-8 levels were estimated from measurements of both total plasma CCK-like immunoreactivity (CCK-LI) and 3H-pCCK-8 activity. PVN injections of CCK-8 and 3H-pCCK-8 produced estimated peak increases in plasma CCK-8 of 15+/-11 and 22+/-3 pM, respectively. The i.v. infusion of CCK-8 doses (0.2 and 1 nmol/kg h) that bracketed the threshold dose for suppression of feeding, increased plasma CCK-LI from a basal level of 6+/-1 to 49+/-10 and 166+/-36 pM, respectively. The i.v. injections of 600 and 4800 pmol of CCK-8 did not suppress feeding. These results suggest that PVN injection of an anorexic 500-pmol dose of CCK-8 does not increase plasma CCK-8 levels sufficiently to suppress feeding by a peripheral mechanism.
Blevins
J E
JE
Veterans Administration Medical Center, Omaha, NE, USA.
Hamel
F G
FG
Fairbairn
E
E
Stanley
B G
BG
Reidelberger
R D
RD
D000818:Animals; D001067:Appetite Depressants / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D004435:Eating / Q000187:drug effects; D007262:Infusions, Intravenous; D007267:Injections; D007275:Injections, Intravenous; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D001067:Appetite Depressants; D012844:Sincalide