Jess L. Miner

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.