The innervation of the hepatic portal vein in the rabbit: ultrastructural evidence against "purinergic" neurotransmission.

The relative density of adrenergic and non-adrenergic nerves in the hepatic portal vein of the rabbit has been determined ultrastructurally. Adrenergic nerves were visualised with the modified chromaffin procedure of Tranzer and Richards (1976). Nearly equal numbers of adrenergic and non-adrenergic nerve profiles were found, indicating a much greater density of innervation by non-adrenergic nerves than that described by Burnstock et al. (1979) using light microscopic histochemical methods. These results imply that part of the argument used by Burnstock et al. (1979) to support "purinergic" transmission in rabbit portal vein is probably invalid.