The human carotid body releases acetylcholine, ATP and cytokines during hypoxia.
Kåhlin J, Mkrtchian S, Ebberyd A, Hammarstedt-Nordenvall L, Nordlander B, Yoshitake T, Kehr J, Prabhakar N, Poellinger L, Fagerlund MJ, Eriksson LI. The human carotid body releases acetylcholine, ATP and cytokines during hypoxia. Exp Physiol. 2014 Aug; 99(8):1089-98.