AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 6 1626-R1631, Copyright © 1994 by American Physiological Society
Stimulation of oxytocin release within the supraoptic nucleus and into blood by CCK-8
I. Neumann, R. Landgraf, Y. Takahashi, Q. J. Pittman and J. A. Russell
Neuroscience Research Group, University of Calgary, Alberta, Canada.
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.
