Characterization of cholecystokinin (cck) binding sites in goldfish
brain and pituitary.
Himick, Beverly A., Steven R. Vigna, and Richard E. Peter.
Department of Biological Sciences, University of Alberta, Edmonton,
Alberta, T6G 2E9 Canada, and *Department of Cell Biology, Duke
University Medical Center, Durham, North Carolina, 27710, USA
APStracts 3:0020R, 1996.
The characterization and distribution of cholecystokinin (CCK)/gastrin
binding sites were determined in the goldfish CNS. Binding of 125I
-sulfated CCK octapeptide (125I-CCK8-s) in tissue sections was found
to be saturable, reversible, time-dependent and displaceable by
CCK/gastrin-like peptides. Analysis of saturable equilibrium binding
revealed a high affinity binding site (Kd of 0.706 + 0.188 nM), which
also displayed high affinity for gastrin17-s and caerulein. Lower
affinities were observed for the non-sulfated forms of CCK8 and
gastrin17. These findings suggest that a single primitive CCK/gastrin
receptor (CCK-X) exists in the goldfish CNS. The distribution of
CCK/gastrin binding sites in the goldfish brain and pituitary
revealed high densities within the telencephalon and preoptic
hypothalamus, as well as within hypothalamic nuclei associated with
the brain feeding center. High densities of binding sites were also
localized within the midbrain tegmentum and optic tectum of the
midbrain, the facial lobe and vagal lobe of the hindbrain, and within
the pituitary pars distalis. Overall, these findings support previous
studies which indicate that CCK/gastrin-like peptides play a role in
the central regulation of feeding behavior and pituitary hormone
secretion in fish (5, 6).
Received 8 June 1995; accepted in final form 2 January 1996.
APS Manuscript Number R351-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96