A Pharmacologic Study on a Possible Inhibitory Role of Dopamine in the Cat Carotid Body Chemoreceptor

Abstract

Catecholamines, mostly dopmaine, are normal constituents of the carotid body of different mammalian species (4,5,7,9,10,11,17). Recent studies on the carotid body chemoreceptor have shown that exogenously applied dopamine induces a marked depression on chemoreceptor discharge frequency (2,15). Consequently, it has been proposed by Zapata (16) that dopamine contained in the carotid body would act as a modulator substance of chemoreceptor activity and would be a part of local regulatory mechanisms. If this is the case in the cat carotid body, drugs affecting dopaminergic receptors in the central nervous system or other organs would also modify the chemoreceptor activity. Therefore, effects of dopaminergic receptor blockking agents (haloperidol and trifluperidol) and a dopaminergic receptor stimulating agent (apomorphine) (8) on cat receptor responses to various stimuli were examined in vivo. Results obtained in the present experiments have provided further evidence for the presence of dopaminergic receptors in the carotid body chemoreceptor, and suggested a possible role of an inhibitory transmitter substance of dopamine in the chemoreceptor function.

The author expressed his sincere gratitude to Dr. F. Takenaka, Department of Pharmacology, Kumamoto University Medical School, Japan for his valuable advise, and to Mr. K. Iwasaki for his technical assistance.