The role of norepinephrine and adrenergic receptors within the hypothalamic paraventricular nucleus in the control of feeding /
Previous studies have shown that microinjection of erogenous norepinephrine (NE) (a noradrenergic agonist) into the medial hypothalamus induced feeding in satiated animals, and pretreatment with alpha-antagonists blocked NE-induced feeding. In contrast, suppression of feeding occurred following inj...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742535111&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Previous studies have shown that microinjection of erogenous norepinephrine (NE) (a noradrenergic agonist) into the medial hypothalamus induced feeding in satiated animals, and pretreatment with alpha-antagonists blocked NE-induced feeding. In contrast, suppression of feeding occurred following injection of various al-adrenergic agonists (phenylpropanolamine, phenylephrine, methoxamine, cirazoline, amidephrine, or SKF 89748) via intra-PVN or systemic injection. Moreover, reversal of this suppression of feeding occurred following pretreatment with an al- adrenergic antagonist (benoxathian or prazosin) . The relationship between endogenous levels of extracellular PVN NE and feeding was uncertain. The diurnal rhythm of endogenous PVN NE and spontaneous feeding during one diurnal cycle in rats was determined by hourly measurement of feeding and microdialysis sampling. Paraventricular NE fluctuated in a bimodal rhythm, with a peak in NE at dark onset and another smaller peak 7 hrs after dark onset. Feeding was greatest at dark onset. The greatest level of PVN NE correlated with feeding at dark onset. The diurnal rhythm of PVN (3H)PRZ receptor binding and (3H)PAC) receptor binding in rats using receptor autoradiography was determined. A rhythm of PVN (3H)PRZ adrenergic receptor binding occurred. The greatest binding occurred during the early part of the light phase. A nonsignificant rhythm in PVN (3H)PAC adrenergic receptor binding occurred. The greatest binding occurred during the latter part of the dark phase. Feeding was greatest at dark onset, and food intake remained elevated during the dark phase. These data suggest that PVN NE and feeding, and a2 adrenergic binding and feeding correlate around dark onset. Mild stress significantly increased PVN NE 40 min after application. Similarly, tyramine injected into the PVN produced a dose-dependant increase in PVN NE. Although NE increased following these manipulations, a concomitant increase in feeding was not observed. These results suggest that increased stress or tyramine were not activating the feeding system. It is possible that elevated levels of PVN al adrenergic receptors were over-riding a feeding signal generated by stress or tyramine. |
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| Item Description: | Vita. "Major Subject: Veterinary Physiology". |
| Physical Description: | xi, 160 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |