The distribution of biogenic amines in the carotid bifurcation region.

1. The distribution of phenolic amines in the carotid body and of adrenergic nerves in the arterial walls of the carotid bifurcation region was investigated histochemically using the phenolic amine-formaldehyde gas condensation reaction, with supplementary electron microscopical examination. Studies were conducted on normal rabbits and on rabbits after superior cervical ganglionectomy.2. The glomus cells of the carotid body contain phenolic amines. The cellular amine persists after long-term sympathetic ganglionectomy.3. The blood vessels supplying the carotid body receive an adrenergic innervation which disappears following superior cervical ganglionectomy.4. The walls of the carotid sinus contain adrenergic nerve fibres derived from the superior cervical ganglion.5. There is no penetration of the arterial tunica media by vasomotor fibres in any part of the carotid bifurcation region.6. Ultimate terminations of adrenergic nerves upon smooth muscle occur across the medio-adventitial border of the common, internal and external carotid arterial walls but only in relation to smooth-muscle cells in the adventitia of the carotid sinus wall.