J. A. Paterson

Cholecystokinin concentration in specific brain areas of rats fed during the light or dark phase of the circadian cycle

Measurement of peptide concentration in specific areas can be used as an initial investigative method for identifying brain sites in which the peptides may be acting. In this study cholecystokinin (CCK) concentration in specific hypothalamic and hindbrain areas of male Sprague-Dawley rats was measured in order to determine whether changes occurred as a result of feeding activity during different portions of the circadian cycle. Three groups of 40 rats each were studied: Group 1 were fasted 16 hr during the dark phase then sacrificed immediately or after a 20 min light phase meal. Group 2 were fasted 16 hr during the light phase then sacrificed immediately after lights out or after a 20 min dark-onset meal. Group 3 were fed ad lib and sacrificed immediately after light out or after a 20 min dark-onset meal. CCK was extracted from dissected areas and concentration was measured by RIA. There was no difference in CCK concentration of any of the 9 brain areas in rats fasted during the dark phase and fed during the light phase. In rats fasted during the light phase CCK concentration of the paraventricular nucleus (PVN) was greater in those that subsequently ate a meal at dark-onset than in those that did not eat (p less than 0.05). In ad lib fed rats CCK concentration was less in the anterior hypothalamus (AH) and greater in the supraoptic nucleus (SON) in rats that ate a dark-onset meal than in rats that did not (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha2-adrenoceptor blockade does not block feeding induced by neuropeptide Y in sheep

We tested the hypothesis that blockade of central alpha 2-adrenergic receptors would prevent neuropeptide Y (NPY)-induced feeding. Nine young female sheep were fitted with lateral ventricula cannulas. Bolus intracerebroventricular (ICV) injection of 3 nmol of NPY increased feed intake after 30 min between 45 and 153% in three experiments. A bolus ICV injection of 400 or 100 nmol of the alpha 2-antagonist, yohimbine, either 5 or 30 min before NPY injection, did not attenuate this response. Instead, yohimbine increased feed intake over NPY-induced feeding by 52 to 55%. We interpret these data as evidence that the putative NPY feeding pathway in feed-sated sheep is not dependent on the type of alpha 2-adrenergic mechanism which can be blocked by ICV injection of yohimbine.

Effects of endophyte-infected tall fescue, environmental temperature and prazosin injection on the rat☆

Effects of an alpha 1 antagonist, prazosin, injection on the rat (Rattus rattus) exposed to warm vs normal environments and fed endophyte-infected (E+) or -free (E-) tall fescue seed were studied. Rats were injected IP daily with placebo or prazosin (1 mg/kg BW). Daily skin and rectal temperatures and food intake measurements were recorded. Selected brain tissues were dissected to determine treatment effects on monoamine receptor density. Rats fed E+ and injected with placebo had reduced (P < 0.01) food intake compared with all other treatments. By day 5 of injection, an endophyte x temperature interaction for increased (P < 0.03) skin and rectal temperatures was measured when rats were fed E+ and housed at 32 degrees C. Also by day 5, injection of rats consuming E+ with prazosin reduced (P < 0.01) skin and rectal temperatures 0.4 degree C compared with those consuming E+ and injected with placebo. Monoamine receptor (alpha 1, alpha 2, and D2) densities were similar (P > 0.10) among treatments. Prazosin injection reduced E+ induced body temperature increases chronically and increased food intake acutely to E- levels. Monoamine receptor densities were unchanged; therefore, E+ effects via monoamine receptors may be due to acute modulation of receptor-associated activity.

Nitrogen balance and abomasal protein-nitrogen flow in growing ruminants fed methane digester effluent in combination with distillers dried grains

Two experiments were conducted to compare dry matter and nitrogen (N) digestibilities, N balance (heifers and lambs) and abomasal N flow (lambs) of ruminants offered ensiled, cracked maize—maize cob diets supplemented with either methane digester effluent (MDE), distillers dried grains (DDG), MDE + DDG (50% of the supplemental N from each) or soyabean meal (SBM). Dry matter digestibility of the diets was similar (avg. 68.4%, heifer; 65.4%, lambs), but N digestibility was lowest (P 0.10) between MDE and DDG (58.5 vs. 57.7%) when lambs were utilized. Nitrogen balance was lower for MDE (6.0 g/day, heifers; 1.8 g/day, lambs) compared with DDG (16.4 g/day, heifer; 3.3 g/day, lambs) but the MDE + DDG combination resulted in an increased balance similar (P > 0.10) to that of SBM (13.3 g/day, heifers; 3.2 g/day, lambs). Total|N flowing past the abomasum was lowest for MDE (14.6 g/day) and highest for DDG (16.9 g/day) with intermediate values observed for MDE + DDG (16.2 g/day) and SBM (15.1 g/day). No differences in nonprotein N flow rates were measured (avg. 7.0 g/day) but protein N flow was lower (P < 0.10) for MDE (6.8 g/day) compared with DDG (9.4 g/day). Higher quantities of total abomasal N appeared to be associated with the protein N fraction. Adding DDG to MDE resulted in a protein N flow rate similar to SBM (7.8 vs. 7.5 g/day). These data indicate that N balance was lower for MDE compared with DDG, MDE + DDG or SBM and may be the result of a reduction in quantity of protein N presented to the small intestine. Replacing 50% of the supplemental N supplied by MDE with DDG increased N balance and abomasal protein N flow to a level equivalent with SBM.