RT Journal Article
SR Electronic
T1 Blockade of ganglionic afterdischarges by tyramine may be mediated by endogenous catecholamines.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 376
OP 379
VO 228
IS 2
A1 D Christ
A1 T Zitaglio
YR 1984
UL http://jpet.aspetjournals.org/content/228/2/376.abstract
AB Tyramine reduced the compound postganglionic action potential from preganglionic stimulation of the golden hamster isolated stellate ganglion at 0.2 Hz. This action of tyramine was only slightly reduced by phentolamine (10(-5)M), an alpha adrenoceptor antagonist. Tyramine also reduced the postganglionic discharges after preganglionic stimulation at 30 Hz for 2 sec in the presence of hexamethonium. The blockade of afterdischarges by tyramine was markedly reduced by phentolamine. Furthermore, tyramine was much less effective in blocking ganglia from reserpine-pretreated hamsters (6 mg/kg, 4 hr before isolation). Blockade of afterdischarges by norepinephrine was reduced by phentolamine, but not by reserpine. These results indicate that the blockade of afterdischarges with tyramine is mediated by endogenous catecholamines. The blocking action of tyramine was not reduced by cocaine (10(-5)M). Cocaine did reduce the afterdischarges, and this action of cocaine was partially antagonized by phentolamine and reserpine. These results suggest that the blockade of afterdischarges by tyramine and cocaine is due to inhibition of catecholamine uptake which potentiates the actions of endogenous catecholamines.