Sodium appetite in the sham drinking rat after chorda tympani nerve
transection.
Frankmann, Sandra P., Suzanne I. Sollars, Ilene L. Bernstein.
Cornell University Medical College, Bourne Behavioral Research
Laboratory, 21 Bloomingdale Rd, White Plains, NY 10605, University of
Washington, Department of Psychology, NI-25, Seattle, WA 98195
APStracts 3:0059R, 1996.
Sodium depletion in the neurologically intact rat produces a prompt
and robust intake of NaCl. Following chorda tympani nerve transection
(CTX) there is a longer latency and a reduced intake of NaCl. The CTX
rat depends on remaining gustatory and postingestive information to
direct NaCl intake. In the present study, the effect of the removal
of the postingestive signals of ingested NaCl (by means of a chronic
gastric fistula) on the NaCl intakes and licking patterns of
neurologically intact (INTACT) and CTX rats were studied. When the
gastric fistula was open ingested NaCl did not pass beyond the
stomach thus, negative postingestive stimulation was absent.
Following overnight sodium-depletion, when postingestive stimulation
was present (i.e. gastric fistula closed; REAL), the CTX group drank
significantly less 0.3M NaCl than the INTACT group over the 2h test
(11.7 +/- 1.6 (CTX) vs 15.3 +/- 2.8 (INTACT) ml). In contrast, when
postingestive signals were absent (i.e. gastric fistula open; SHAM)
the INTACT group ingested 52.5 +/- 4.4 ml whereas the CTX group had
ingested only 12.4 +/- 3.1 ml of 0.3M NaCl. Lickometer data analysis
revealed that even during the first minute of the test the CTX/REAL
group generated significantly fewer licks than any of the other
groups. Thus, although the CTX group was sensitive to inhibitory
postingestive signals in the early portion of the appetite test, the
absence of these signals did not release the robust and sustained
intake of NaCl characteristic of the neurologically intact group.
These results suggest that information provided by the chorda tympani
nerve is critically important to the strong motivational properties
of NaCl after sodium-depletion.
Received 1 June 1993; accepted in final form 13 February 1996.
APS Manuscript Number R302-3.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96