Abstract

The effects of blocking agents upon the depression of transmission of the combined stellate and caudal cervical ganglia produced by the close intra-arterial injection of norepinephrine have been studied in the anesthetized dog. The results of this study showed that combined nicotinic and muscarinic ganglion blockade with chlorisondamine and atropine did not decrease the amount of norepinephrine-produced depression of transmission. This depression of ganglion transmission was converted to a stimulation by the close intra-arterial administration of the alpha adrenergic blocking drug phentolamine. Blockade of all preganglionic impulses by the production of total spinal anesthesia blocked the depression of ganglion transmission produced by norepinephrine and prevented the conversion of this depression to a stimulation by phentolamine. Phentolamine, when administered by close intra-arterial injection, produced a dose-dependent, prolonged stimulation of transmission through the ganglia. The results of this study infer that the norepinephrine depression of ganglion transmission is at some site other than the usual muscarinic and nicotinic ganglion pathways and that spinal pathways are involved.