M. Moriarty et al., DESENSITIZATION BY NEUROPEPTIDE-Y OF EFFECTS OF SYMPATHETIC-STIMULATION ON CARDIAC VAGAL ACTION IN ANESTHETIZED DOGS, Journal of the autonomic nervous system, 45(1), 1993, pp. 21-28
The effects of a long-lasting intravenous infusion of neuropeptide Y (
NPY, 180 +/- 8 min, 53 +/- 4 mug/kg/h) on the prolonged inhibition of
cardiac vagal action evoked by cardiac sympathetic nerve stimulation a
nd bolus intravenous injections of NPY were investigated in anaestheti
sed dogs. Sympathetic stimulation and NPY injection were performed on
four separate occasions: once in control conditions, then once early a
nd again late in the period of NPY infusion, and then on a final occas
ion 60-90 min after the cessation of NPY infusion. The maximum inhibit
ion of cardiac vagal action evoked by an injection of NPY was signific
antly less late in the NPY infusion when compared with the other three
injection groups (ANOVA, P < 0.001). Also the time to half-recovery o
f this response was significantly less than that seen in the other thr
ee injection groups (ANOVA, P < 0.001). The maximum inhibition of card
iac vagal action evoked by sympathetic stimulation was significantly r
educed late in the NPY infusion when compared with the other three sti
mulation groups (ANOVA, P < 0.0001). The time for half-recovery of thi
s response was also less than that of the other three stimulation grou
ps (ANOVA, P < 0.001). The results indicate that desensitisation of th
e vagal attenuation to both exogenous NPY and sympathetic stimulation
occurred during a long-lasting period of NPY infusion. This is consist
ent with the proposal that NPY is a mediator of this sympathetic-evoke
d vagal attenuation.