Sucrose drinking reduces dorsal hypothalamic beta-endorphin levels in spontaneously hypertensive rats but not in Wistar-Kyoto rats.
The present study was performed to test whether drinking of a 10% sucrose solution would preferentially alter tissue content of beta-endorphin in dorsal and ventral hypothalamic fragments from the spontaneously hypertensive rat (SHR), as opposed to the Wistar-Kyoto rat (WKY). Changes were correlated with cardiovascular function and circulating catecholamine levels to assess the role of hypothalamic beta-endorphin, a putative mediator of sucrose-induced changes in cardiovascular sympathetic nervous tone. Male rats were trained to consume their total 24-h water intake in a single period between 0900-1100 h. Catheters were chronically implanted to sample blood and to record arterial blood pressure and heart rate. The experimental protocol consisted of a recording session, which included a 10-min drinking period wherein rats consumed 8 ml of either sucrose solution or deionized water. Rats were sacrificed and hypothalami removed for analysis of beta-endorphin content. Comparable increases in blood pressure were noted in SHR and WKY during drinking of either sucrose or water. Drinking-induced tachycardia was blunted in SHR drinking sucrose. Plasma norepinephrine was increased only in sucrose-drinking SHR. Plasma glucose levels were elevated in both SHR and WKY following drinking of sucrose, but not water. beta-Endorphin levels were reduced (p < 0.05) in dorsal, but not ventral, hypothalamic fragments only in SHR drinking sucrose. The sucrose-induced changes in beta-endorphin did not correlate with blood pressure responses. The results indicate an exaggerated stimulation of beta-endorphin release in the dorsal hypothalamus following sucrose ingestion in SHR.
Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson 39216.
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D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D004326:Drinking; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D011921:Rats, Inbred WKY / Q000378:metabolism*; D013045:Species Specificity; D013395:Sucrose / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
D001786:Blood Glucose; D013395:Sucrose; D001615:beta-Endorphin; D009638:Norepinephrine; D004837:Epinephrine