The norepinephrine and dopamine content of the cat carotid body in vivo under normoxic and hypoxic conditions.

The norepinephrine (NE) and dopamine (DA) content of the cat carotid body (CB) in vivo was investigated under normoxic and hypoxic conditions (5% O2 for 1 h) by radiolabelling method. To avoid a large scattering of the measured values due to inhomogeneity of the biological material, young sib animals were used. The mean NE content under normoxia was 617 +/- 184 pmol/CB, and the mean DA content 451 +/- 200 pmol/CB. Under hypoxia, NE and DA were lowered significantly by 37% and 30%, respectively. From these results we conclude that both transmitters with their known excitatory and inhibitory actions probably influence the chemoreceptive elements in the carotid body.