Lg. Ulman et al., GALANIN ANTAGONIST EFFECTS ON CARDIAC VAGAL INHIBITORY ACTIONS OF SYMPATHETIC-STIMULATION IN ANESTHETIZED CATS AND DOGS, Journal of physiology, 464, 1993, pp. 491-499
1. Galantide, a putative galanin antagonist composed of twenty amino a
cids, caused a significant reduction in the vagal attenuating action o
f galanin injection (20 mug/kg; 6-2 nmol/kg) in anaesthetized cats at
both ten times (137 mug/kg; 62 nmol/kg) and twenty-five times (343 mug
/kg: 156 nmol/kg) the molar dose of galanin. Galantide did not block t
he depressor action of galanin in these animals. 2. Galantide, at both
doses, also significantly reduced the vagal attenuating action of a 5
min period of cardiac sympathetic stimulation at 16 Hz in anaesthetiz
ed cats. 3. In anaesthetized dogs, galantide, at the same dose used in
cats (137 mug/kg; 62 nmol/kg) had no significant effect on the vagal
attenuation evoked by cardiac sympathetic stimulation or injection of
neuropeptide Y (35 mug/kg; 8-2 nmol/kg). 4. This study therefore demon
strates antagonist properties of galantide on the vagal inhibitory act
ion of galanin. It supports the hypothesis that the vagal inhibitory f
actor released by cardiac sympathetic nerve stimulation in the cat, bu
t not the dog, is galanin, although it does not exclude the possibilit
y of other factors playing a more minor role. Because galantide was no
t shown to block the depressor action of galanin, this study also sugg
ests that there may be more than one galanin receptor subtype.