Monoamines and their catabolites in the rabbit carotid body

Monoamines and their metabolites have been measured by high performance liquid chromatography with electrochemical detection, in control rabbit carotid bodies and under several experimental conditions: 1) at different times (3 h, 6 h, 24 h, 48 h) after intravenous injection of reserpine (5 mg/kg); 2) 14 days after sympathectomy; 3) 14 days after section of the carotid sinus nerve. The results were analyzed with probability plotting methods. Dopamine was the most important monoamine in the carotid body (CB) and its variations were very large. It was almost entirely depleted by reserpinization without simultaneous increase in 3,4-dihydroxyphenylacetic acid. Sympathectomy increased dopamine content but did not change noradrenaline content. However data analysis suggested that noradrenaline might be compartmented in two pools: one with a large variance, located in the type I cells was increased after sympathectomy, the other, more constant, located in the sympathetic nerve endings was entirely depleted after sympathectomy. Section of the carotid sinus nerve increased dopamine and noradrenaline and quadrupled the serotonin content of the CB. It is proposed that carotid sinus and sympathetic innervations regulate the monoamine metabolism of the CB.