Characterisation of nitrergic transmission in the isolated anococcygeus muscle of the female mouse

Field stimulation of anococcygeus muscles from female mice produced frequency-dependent relaxations of carbachol-induced tone, which were independent of the oestrus cycle but were abolished by the nitric oxide synthase (NOS) inhibitor L-NG-nitroarginine (L-NOARG; 100 mu M) and the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxodiazolo[4,3-a]quinoxalin-1-one (ODQ; 5 mu M); L-NOARG inhibition was reversed by L-, but not D-arginine. The selective phosphodiesterase V inhibitor zaprinast (1-130 mu M) directly relaxed tone and enhanced both the amplitude and duration of field stimulation-induced relaxations; the effect on amplitude was greater at lower frequencies of stimulation, while increased duration dominated at higher frequencies. The duration, but not the amplitude, of relaxations to exogenous nitric oxide (NO; 15 mu M) was also increased by zaprinast. The mouse anococcygeus provides a useful model for pharmacological investigation of nitrergic neurotransmission in female urogenital smooth muscle. (C) 1999 Elsevier Science B.V. All rights reserved.