Stimulation of oxytocin release within the supraoptic nucleus and into blood by CCK-8.
Simultaneous microdialysis in brain and blood was used to monitor the effects of systemic and central cholecystokinin octapeptide (CCK-8) on the release of oxytocin and vasopressin within the hypothalamic supraoptic nucleus (SON) as well as into blood of urethan-anesthetized female rats. Administration of CCK-8 (20 micrograms/kg iv) increased oxytocin contents in 30-min microdialysates sampled simultaneously within the SON (1.8-fold) and blood (2.4-fold, both P < 0.05) compared with prestimulation levels. In another experiment, after bilateral administration of CCK-8 directly into the SON (10 ng/0.5 microliter) via a microdialysis/infusion probe, oxytocin contents in dialysates sampled from the left and right SON were increased 2.3- and 1.7-fold (P < 0.05), respectively. In simultaneously sampled dialysates from the jugular vein, oxytocin content increased 2.3-fold (P < 0.05). In contrast, oxytocin in dialysates sampled outside the hypothalamic nuclei was not altered by systemic or central CCK-8. The direct infusion of CCK-8 into both SON increased the release of vasopressin within the SON 1.7-fold (P < 0.05) but failed to significantly change vasopressin release into blood. The present findings show a coordinated regulation of intranuclear and systemic release of oxytocin in response to systemic and central CCK-8 and provide further evidence for a possible involvement of endogenous oxytocin in the complex regulation of ingestive and reproductive behaviors induced by CCK-8 at the brain level.
Neumann
I
I
Neuroscience Research Group, University of Calgary, Alberta, Canada.
Landgraf
R
R
Takahashi
Y
Y
Pittman
Q J
QJ
Russell
J A
JA
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D005260:Female; D007275:Injections, Intravenous; D017551:Microdialysis; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000008:administration & dosage / Q000494:pharmacology*; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000378:metabolism*
D001127:Arginine Vasopressin; D010121:Oxytocin; D012844:Sincalide