Intracranial Injections of 5-HT and db cAMP and Feeding in Sheep and Cattle

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Abstract
The effect on feeding of 5-HT (5-hydroxy-tryptamine in sheep and cattle, and whether this effect could be mediated by cyclic adenosine monophosphate (cAMP) was tested. Steers (n = 8) and wethers (n = 8) were surgically prepared with lateral ventricular guides. Feed intake was increased (P<.05) by administration of 5-HT, dissolved in synthetic CSF (sCSF), into the lateral ventricles of both steers and wethers. Wethers (n = 16) prepared with hypothalamic guides were injected with 1.0 μ sCSF or 8, 32, 128, and 512 nmoles of either 5-HT or the dibutyryl derivative of cAMP (db cAMP) dissolved in synthetic CSF. Data were grouped according to injection sites based on histological examination of the brains (dorso-anterior, ventro- and dorsomedial, and anterior perifornical hypothalamus, and anterior commissure). Feeding increased following injection of 32 and 128 nmoles (263% and 257% of control, respectively) of 5-HT into the anterior commissure region, and 512 nmoles (384% of control intake) of 5-HT into the ventro- and dorsomedial hypothalamus (P<.05). Only one dose of db cAMP (8 nmoles) increased feeding and only when injected into the anterior commissure (P<.01). It is concluded that feeding occurs in response to 5-HT injected into distinct areas of the brain, but exogenous db cAMP does not consistently elicit feeding in these areas. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.