Inhibitory effect of propofol on sympathetic neurotransmission results in changes of plasma neuropeptide Y in rats

1 The effects of propofol on sympathetic neurotransmission and changes of plasma level of neuropeptide Y-like immunoreactivity (NPY-ir) were investigated in rats. 2 Intraperitoneal injection of propofol into rats lowered the systemic blood pressure and plasma NPY-ir in a dose-dependent manner. 3 Decrease of plasma NPY-ir induced by propofol was not modified in adrenalectomized rats, In the activation of adrenergic neurotransmission by a ganglionic nicotinic agonist, elevation of plasma NPY-ir was also reduced by propofol indicating the direct effect on peripheral adrenergic nerve terminals. 4 Plasma level of NPY-ir reversed in parallel with the recovery of anaesthesia induced by propofol. After an intracerebroventricular injection of propofol into the rats, both the lowering of plasma NPY-ir and the induction of anaesthesia were observed. Thus, a central nervous system effect of propofol can also be considered in its effect on plasma NPY-ir. 5 The data suggest that propofol has the ability to lower plasma NPY-ir in rats through an inhibition of adrenergic neurotransmission via central nervous pathway and/or peripheral nerve terminal blockade.