“…Catecholamines and indolamine are known to be normally present in the carotid body of different mammalian species (Lever, Lewis & Boyd, 1959;Niemi & Ojala, 1964;Fillenz & Woods, 1966;Hamberger, Ritzen & Wersall, 1966;Chiocchio, Biscardi & Tramezzani, 1966I-Li Chen, Yates & Duncan, 1967;Zapata, Hess, Bliss & Eyzaguirre, 1969;Kobayashi, 1971;Chiocchio, King, Carballo & Angelakos, 1971 (Eyzaguirre & Koyano, 1965;Eyzaguirre & Zapata, 1968;Zapata et al, 1969), although other evidence indicates otherwise (Biscoe, 1965;Sampson, 1972;Andrew, Black, Comroe & Jacobs, 1972). A physiological role for 5-hydroxytryptamine (5-HT) may not be discarded, since the carotid body contains a certain amount of 5-HT (Chiocchio et al, 1967(Chiocchio et al, , 1971; furthermore, histochemical methods have shown that 5-HT is located in the electron-dense core vesicles of the Type I cells (Chiocchio et al, 1967;I-Li Chen et al, 1967).…”