Failure of presynaptic purinoceptors to modulate noradrenaline release from sympathetic nerves in human dental pulp

The effects of putative presynaptic P1- and/or P2-purinoceptors on the rele ase of noradrenaline from sympathetic nerves in human dental pulp were exam ined by testing the effects of agonists and an antagonist of these receptor s on the stimulation-induced overflow of [H-3]noradrenaline from tissue tre ated with desipramine (0.3 mu mol/l) and preincubated with [H-3]noradrenali ne (0.6 mu mol/l). The P1-purinoceptor agonists adenosine (1.0 mmol/l) and 2-chloroadenosine (0.01-1.0 mmol/l) and the antagonist 8-cyclopentyl-1,3-di propyl xanthine (1.0 mu mol/l), and the P2-purinoceptor agonists ATP (0.1 m mol/l) and beta,gamma-methylene-ATP (0.01 mmol/l), did not modulate the rel ease of noradrenaline. Adenosine was also without effect in dental pulp tre ated with the alpha(2)-adrenoceptor antagonist rauwolscine. It is concluded that presynaptic P1-purinoceptors and those P2-purinoceptors activated by adenine nucleotides are either not present on sympathetic nerves in human d ental pulp or that they exert little or no effect on the release of noradre naline. (C) 2000 Elsevier Science Ltd. All rights reserved.