title: Comparison of the effects of prostaglandins E2 and I2 on testicular nociceptor activities studied in vitro.
abstract: Effects of exogenous prostaglandin (PG) E2 and PGI2 on testicular polymodal receptor activities were compared in in vitro recordings of single- or multi-fiber discharges from canine testis-spermatic nerve preparations. PGI2 up to 1.4 x 10(-6) mol/l (cumulative method) or 1.0 x 10(-5) mol/l (non-cumulative method) excited only weakly some of the receptors, and similar observations were made with PGE2. Both PGs applied cumulatively or non-cumulatively at concentrations above 1.4 x 10(-8) mol/l augmented the response to bradykinin (9.4 x 10(-8) mol/l) in more than half of the cases tested. The augmenting effect of PGE2 lasted longer than that of PGI2 both with the cumulative and the non-cumulative method. The degree of augmentation tended to increase dependent on concentration, but some cases showed no further increase or rather a decrease in augmentation by PGs at a ten times higher concentration, especially when PGs were applied cumulatively. A second challenge by PG after a short interval (2 min) did not induce augmentation. These phenomena were considered to be tachyphylaxis to PGs. Cross-tachyphylaxis to PGE2 and PGI2 was also observed. There was not much difference in excitatory and augmenting potencies between these two PGs, but there was a clear difference in the concentrations of the PGs necessary to induce excitation of polymodal receptors and to facilitate their response to bradykinin.
authors.affiliation: Department of Nervous and Sensory Functions, Nagoya University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Mizumura
authors.forename: J
authors.initials: J
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Kumazawa
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology*; D004285:Dogs; D011464:Epoprostenol / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D013618:Tachyphylaxis / Q000502:physiology; D013737:Testis / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D011464:Epoprostenol; D015232:Dinoprostone; D001920:Bradykinin