Creighton University School of Medicine
Department of Biomedical Sciences
CHOLECYSTOKININ ACTION AT CCKA
RECEPTORS IN THE BRAIN TO PRODUCE
SATIETY IN RATS
Ph.D. Thesis Defense
By
Daniel A. Castellanos
May 18, 2001
10:00 A.M.
Criss III, Room 459
Summary
Cholecystokinin (CCK) is a peptide that is found
throughout the brain and in neurons and endocrine cells
of the gastrointestinal tract. Studies demonstrating that
systemic administration of the CCKA receptor antagonist
devazepide increases food intake in a variety of species
provide compelling evidence that CCK plays an essential
role in producing the satiation that occurs with ingestion
of a meal. Given that devazepide readily penetrates the
blood-brain barrier, it remains to be determined whether
endogenous CCK is acting peripherally, within the brain,
or at multiple peripheral and central sites to produce
satiety.
doctoral program at Creighton University in August 1991. In
1999 he began working at the University of Miami,
Department of Neurological Surgery, The Miami Project to
Cure Paralysis.
Graduate Committee
Roger D. Reidelberger, Ph.D. (Major Advisor)
In this study we used the CCKB receptor
antagonist L365, 265, and two different CCKA receptor
antagonists, devazepide, which freely crosses the blood
brain barrier, and A70104, which does not, to further
define the receptor subtype and site of action of
endogenous CCK to produce satiety. Experiments were
designed to 1) determine whether endogenous CCK acts
at CCKA or CCKB receptors to inhibit food intake; 2)
determine whether endogenous CCK acts as an
essential satiety factor at different times across the
diurnal cycle; and 3) determine whether endogenous
CCK acts at CCKA receptors central or peripheral to the
blood brain barrier to produce satiety.
Richard F. Murphy, Ph.D.
Robert Creek, Ph.D.
Thomas E. Adrian, Ph.D.
William Jefferies, Ph.D.
These experiments produced several new
findings. First, IV injection of the CCKA receptor
antagonist devazepide at a dose that stimulates food
intake in rats (1mg kg-1), had no effect on
Biography:
Mr. Daniel Castellanos graduated from University of
Nebraska with an MS in Biology in 1987. He began his
duodenal delivery of oleic acid in rats. Am. J. Physiol. 269:
R1420-R1433, 1995.
Castellanos,D.A. and R.D. Reidelberger. Duirnal variation
in the effects of type A CCK receptor antagonist
devazepide on meal pattern in rats. Ann. N.Y. Acad.Sci.
713:429-430, 1994.
Reidelberger, R.D., V. Gabor, L. Ralf-Marco, D.A.
Castellanos, G.L. Rosenquist, H.C. Wong, and J.C.
Walsh. Cholecystokinin suppresses food intake by a
nonendocrine mechanism in rats. Am. J.
Physiol.267:R901-R901, 1994.
Blevins, J.E., R.B. Mackin, J.A. Knezetic, D.A.
Castellamos and R.D. Reidelberger. Effects of
intravenous and paraventricular nucleus injections of
leptin on food intake in rats. Appetite27:267, 1996
(abstract)
Gastrin-induced stimulation of gastric acid secretion in
rats, an action that is mediated by the CCKB receptor
,and that was blocked by the CCKB receptor antagonist
L365, 260. This finding further supports the hypothesis
that endogenous CCK acts at CCKA receptors, not
CCKB receptors, to produce satiety. Second, IV injection
of the CCKA receptor antagonist devaepide significantly
stimulated cumulative 4-h food intake at 0, 16 and 20 h
after dark onset by 31%, 54%, and 40% respectively, yet
had no effect on food intake at 4, 8 or 12 h after dark onset.
Devazepide-induced increases in food intake occurred
through an increase in meal frequency not meal size.
These results suggest that endogenous CCK plays an
essential role in producing satiety in rats only during
several hours before and after the onset of the dark period.
It is likely that at other times of the day, greater degree of
redundancy in satiety signaling occurs such that CCK
receptor blockade produces little if any effect. Third, IV
infusion of the CCKA receptor antagonist A-70104 (1000
nmol kg-1 h-1) for 3 h during the early dark period
completely reversed the 70% reduction in food intake
produced by a maximal 3-h inhibitory dose of CCK-8 (10
nmol kg-1 h-1 IV). In contrast, this dose of A-70104 had no
effect on food intake when administered alone under the
same conditions in which devazepide (1 mg kg-1 IV)
increased food intake by more than 50%. A-70104 (1000
nmol kg-1 h-1) also did not reverse the 40% reduction in
food intake produced by a 2-h duodenal infusion of oleic
acid (460 mol h-1), an effect that was completely reversed
by devazepide. Because devazepide readily penetrates the
blood brain barrier, while A-70104 does not, these results
suggest that endogenous CCK produces an essential
satiety action mediated by CCKA receptors located in brain
regions beyond the blood-brain barrier.
Publications and Manuscripts During Graduate Work
Castellanos, D.A. and R.D. Reidelberger. Effects of
peripheral cholecystokinin receptor blockade on food intake
in rats. Am. J. Physiol., submitted
Schumm,M.A., D.A. Castellanos, and J. Sagen. Chromaffin
cells exert a trophic effect on neural progenitor cells in
vitro. Exper. Neurol., submitted
Sagen,J., D.A. Castellanos, H.M. Bramlett, E.D. Potter,
S. Chen, W.D. Deitrich. Robust survival of neural stem
cell grafts in gray and white matter regions following fluid
percussion brain injury. Amer. Soc. Neural Transpl. And
Repair Abstr. 8:69, 2001 (abstract)
D.A. Castellanos, P. Tsoulfas, B.R. Frydel, C.W. Hunter,
S.R. Rendon, S. Chen, Y. Felipe, and J. Sagen.
Enhanced survival of genetically modified neural stem
cell transplants in the spinal cord following neurotrophin-3
treatment in vivo or in vitro. Soc. Neurosci. Abstr. 26 (1):
873, 2000
M.A. Schumm, D.A. Castellanos, S.A. Mason, B.R.
Frydel, J. Huang and J. Sagen. Chromaffin cells exert a
trophic effect on neural progenitor, cells in vitro. Soc.
Neurosci. Abstr. 26 (1): 899. 2000. (abstract)
Mason, S.A., D.A. Castellanos, C.W. Hunter, B.R. Frydel,
X.T. Nie, and J. Sagen. Adrenal medullary transplants in
th espinal subarachnoid space may provide trophic
support following peripheral nerve injury. Amer. Soc.
Neural Traspl. and Repair Abstr. 7:46, 2000. (abstract)
Schumm, M.A., D.A. Castellanos, S.A. Mason, B.R.
Frydel, and J. Sagen. Trophic effects of chromaffin cells
on neural progenitors in vitro. Amer. Soc. Neural Trasnpl.
and Repair Abstr. 7:42, 2000. (abstract)
Castellanos,D.A., J.F. Kerwin Jr. and R.D. Reidelberger.
Effects of peripheral CCK-A receptor blockade on food
intake in freely feeding rats. Obes Res 3:377S, 1995.
(abstract)
Hunter,C.W., B.R. Frydel, D.A. Castellanos, X.T. Nie and
J. Sagen. Strategies to reduce inflammatory responses to
grafts in the spinal subarachnoid space. Amer. Soc. Neural
Trasnpl. and Repair Abstr. 7:63, 2000. (abstract)
Caban, A.J., J.W. Lee, A. Hama, C.W. Hunter, D.A.
Castellanos and J. Sagen. Nicotinic Agonist epibatidine
enhances the antinociceptive effects of intrathecal adrenal
medullary transplants. Soc. Neurosci. Abstr. 26(1):937,
2000. (abstract)
Bes,J.C., B.R. Frydel, W.M. Walters, E.D. Potter, D.A.
Castellanos, J.P. Brunshwig and J. Sagen. Generation of
chromaffin cell precursors from human embryonic adrenal
gland for potential use in transplantation. Soc. Neurosci.
Abstr. 26(1):829, 2000. (abstract)
Bes, J.C., W.M. Walters, E.D. Potter, D.A. Castellanos,
J.P. Brunschwig and J. Sagen. Ultrastructural
characteristization of chromaffin cell progenitor cultures.
Amer. Soc. Neural Transpl. and Repair Abstr. 7:42, 2000.
(abstract)
Wotman,T., D.A. Castellanos, and R.D. Reidelberger. Role
of cholecystokinin in the anorexia produced by