Neurotensin releases norepinephrine differentially from perfused hypothalamus of sated and fasted rat
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 (/sup 3/H)NE, an artificial cerebrospinal fluid was perfused at the site at a rate of 20 ..mu..l/min over successive intervals of 5.0 min. When 0.05 or 0.1 ..mu..g/..mu..l NT was added to the perfusate, the peptide served either to enhance or educe 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. Taken together, these observations provide experimental support for the view-point that NT could act as a neuromodulator of the activity of hypothalamic noradrenergic neurons that are thought to play a functional role in the regulation of food intake.
- Research Organization:
- Univ. of North Carolina School of Medicine, Chapel Hill
- OSTI ID:
- 6218798
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 252:1
- Country of Publication:
- United States
- Language:
- English
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HYPOTHALAMUS
PHYSIOLOGY
NEUROREGULATORS
BIOLOGICAL EFFECTS
FASTING
NORADRENALINE
PERFUSED TISSUES
RATS
TRITIUM COMPOUNDS
ADRENAL HORMONES
ANIMAL TISSUES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
BRAIN
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
DRUGS
HORMONES
LABELLED COMPOUNDS
MAMMALS
NERVOUS SYSTEM
ORGANS
RODENTS
STEROID HORMONES
SYMPATHOMIMETICS
TISSUES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques