Effects of sigma and phencyclidine receptor ligands on electric field-stimulated rabbit ear artery constriction in vitro

Several ligands of phencyclidine (Phe) receptors: Phe, dizocilpine maleate (Diz, MK-801), 1-[1-(2-thionyl)cyclohexyl] piperidine (TCP), and ligands of sigma (sigma) receptors: dl-N-allylnormetazocine (dl-SK&F-10047), 1, 3-di-ortho-tylyl-guanidine (DTG), dl-pentazocine, were tested on rabbit ear arteries in vitro. It was found that the ligands of Phe receptors enhanced the electric field stimulated vasoconstriction (ESV). Their concentration-effect curves of these compounds were parallel in the order of potencies: Phe > Diz > TCP. The ligands of sigma receptors had no effect on ESV of the arteries, but 5 mumol.L-1 reduced or increased the effect of Phe (5 mumol.L-1) on ESV. d-SK&F-10047, d-pentazocine, and DTG inhibited the effect of Phe on ESV from 364 +/- 22 mg to 142 +/- 49 mg (n = 5, P < 0.01), 262 +/- 95 mg (n = 5, P < 0.05), and 291 +/- 80 mg (n = 5, P > 0.05), respectively. The levoisomers: l-SK&F-10047 and l-pentazocine enhanced the effect of Phe on ESV from 364 +/- 22 mg to 484 +/- 78 mg (n = 5, P < 0.05), and 466 +/- 95 mg (n = 5, P < 0.05), respectively. These results revealed that there were mainly Phe receptors but hardly any sigma receptors in the arteries.