Effects of caffeine on carotid sinus nerve chemosensory discharge
in kittens and cats.
Bairam, A., P. De Grandpr, C. Dauphin, F. Marchal.
Unit_ de n_onatologie, Centre de recherche, Pavillon Saint-Fran_ois
d'Assise, Universit_ Laval, Qu_bec, Canada and Laboratoire de
physiologie, Facult_ de M_decine de Nancy, VandIuvre les Nancy,
France
APStracts 3:0488A, 1996.
Caffeine (C) decreases apneic episodes in premature infants and is
thought to stimulate breathing mainly by a central mechanism. While
the methylxanthines theophylline and aminophylline are known to alter
the carotid chemoreceptor activity, there is little data on C. The
aim of the study was to examine the effects of C on the carotid sinus
nerve discharge (CSND) in developing animals. Nine kittens 17 - 21
days old and 6 adult cats anesthetized and artificially ventilated
were studied. They received four consecutive doses of C, each of 10
mg/kg, administered at intervals of 20 min either as IV bolus
injection (6 kittens, 3 cats) or continuous infusion (3 kittens, 3
cats). Bolus injections of C invariably induced a prompt but
transient increase in the CSND: from 4.1 +/- 0.6 to 8.1 +/- 1.0
imp/sec in kittens (p = 0.01) and from 3.9 +/- 0.1 to 7.9 to 1.0
imp/sec in cats (mean +/- SEM after the first injection). This
response was associated with a significant decrease in arterial blood
pressure. Continuous infusion of C did not induce any early change in
either CSND or blood pressure, in kittens or cats. Fifteen minutes
after beginning C injection or infusion, CSND in air, 8 % O2 in N2 or
100 % O2 were not significantly different from control. Haloperidol
administered at the end of the experiment in 4 cats and 4 kittens
significantly increased CSND and did not suppress the early response
to C injection. It is concluded that caffeine administered by bolus
in the kitten induces a transient stimulation of the CSND, associated
with a decrease in the arterial blood pressure and independent of the
dopaminergic mechanisms in the carotid body. The lack of sustained
effect implies the main mechanism to the ventilatory stimulation by C
must be central.
Received 7 March 1996; accepted in final form 15 October 1996.
APS Manuscript Number A232-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996