Studies on the functional role of alpha-adrenoceptors in the cardiac sympathetic ganglia of the dog.
Inhibitory alpha-adrenoceptors were studied in cardiac ganglia of pentobarbital-anesthetized dogs. Blockade of alpha 1- or alpha 2-adrenoceptors augmented preganglionic nerve stimulation induced tachycardia without altering the response to postganglionic nerve stimulation. The effect produced by blockade of ganglionic alpha 1-adrenoceptors with terazosin had different frequency-response characteristics from, was of smaller magnitude than, and was additive with the effect produced by blockade of ganglionic alpha 2-adrenoceptors with rauwolscine. The response to activation of ganglionic nicotinic cholinergic receptors in the absence of electrical stimulation of the preganglionic nerve was not affected by blockade of either alpha 1- or alpha 2-adrenoceptors. The response to nicotinic cholinergic receptor activation during periods of continuous preganglionic nerve stimulation was augmented following blockade of alpha 2-adrenoceptors but unaffected by alpha 1-adrenoceptor blockade. These results suggest that there are two different inhibitory pathways involving alpha-adrenoceptors in mammalian sympathetic ganglia and provide evidence that these inhibitory pathways are operative under the experimental conditions of ganglionic transmission.
Horn
P T
PT
Department of Pharmacological and Physiological Sciences, University of Chicago, IL 60637.
Kohli
J D
JD
D000818:Animals; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D005728:Ganglia, Sympathetic / Q000502:physiology*; D006321:Heart / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011978:Receptors, Nicotinic; D015016:Yohimbine; D004246:Dimethylphenylpiperazinium Iodide; C041226:Terazosin; D011224:Prazosin