AJP - Endocrinology and Metabolism, Vol 252, Issue 1 E102-E109, Copyright © 1987 by American Physiological Society
Neurotensin releases norepinephrine differentially from perfused hypothalamus of sated and fasted rat
T. F. Lee, A. H. Rezvani, J. R. Hepler and R. D. Myers
The central injection of neurotensin (NT) has been reported to attenuate
the intake of food in the fasted animal. To determine whether endogenous
norepinephrine (NE) is involved in the satiating effect of NT, the in vivo
activity of NE in circumscribed sites in the hypothalamus of the
unanesthetized rat was examined. Bilateral guide tubes for push-pull
perfusion were implanted stereotaxically to rest permanently above one of
several intended sites of perfusion, which included the paraventricular
nucleus (PVN), ventromedial nucleus (VMN), and the lateral hypothalamic
(LH) area. After endogenous stores of NE at a specific hypothalamic locus
were radiolabeled by microinjection of 0.02-0.5 mu Ci of [3H]NE, an
artificial cerebrospinal fluid was perfused at the site at a rate of 20
microliter/min over successive intervals of 5.0 min. When 0.05 or 0.1
micrograms/microliter NT (0.03-0.6 mM) was added to the perfusate, the
peptide served either to enhance or reduce the local release of NE at 50%
of the sites of perfusion. In these experiments, the circumscribed effect
of NT on the characteristics of catecholamine efflux depended entirely on
the state of hunger or satiety of the rat. That is, when NT was perfused in
the fully satiated rat, NE release was augmented within the PVN or VMN;
conversely, NE release was inhibited in the LH. In the animal fasted for
18-22 h, NT exerted an opposite effect on the activity of NE within the
same anatomical loci in that the efflux of NE was enhanced in the LH but
attenuated or unaffected in the PVN or VMN.(ABSTRACT TRUNCATED AT 250
WORDS)
