Responses of smooth muscle strips from penile erectile tissue to drugs and transmural nerve stimulation

Abstract

1. The mechanical response to drugs and to electrical stimulation of nerves was investigated in isolated strips of intrinsic smooth muscle from the corpora cavernosa penis of the rat. 2. Noradrenaline caused muscle strips to contract in a dose-dependent manner. Contractions could be blocked by pretreatment with the alpha-adrenoreceptor antagonist, phentolamine. 3. Acetylcholine and carbachol had no effect on the baseline tension of muscle strips. Both drugs were relatively ineffective in relaxing noradrenaline-contracted strips. 4. Field stimulation of isolated muscle strips elicited contractions which were blocked by tetrodotoxin and greatly attenuated with phentolamine or reserpine pretreatment. Acetylcholine inhibited the excitatory response to field stimulation. This inhibitory effect of acetylcholine could be blocked with atropine. 5. Field stimulation of noradrenaline-contracted muscle strips caused relaxation. This inhibitory effect, due to nerves which arise from the pelvic plexus, is unaffected by substances which act on cholinergic systems. 6. The results suggest that the erectile muscle of the rat is similar to that of man in that it receives an excitatory noradrenergic innervation and an inhibitory innervation which may have a non-cholinergic component. Although acetylcholine may have a role in penile physiology of the rat, it is unlikely that it has a postsynaptic action.

Endothelial and neuronal-derived nitric oxide mediated relaxation of corpus cavernosal smooth muscle in a rat, in vitro, model of erectile function

“…This value was chosen from published data. 20,21 In our experience, application of this range of resting tension resulted in inconsistent contractions.…”

“…There is very limited data on the use of the rat as an in vitro model of erectile function. Initial descriptions of two different corpora cavernosal in vitro models have not been followed up by the authors that developed them, 20,21 although other groups have adapted their techniques. 22 ± 25 There is controversy over the role of eNOS in the rat and whether it is a good model of human corpora cavernosal function.…”

Characterization of inhibitory neurotransmission in the isolated corpus cavernosum from rabbit and man.

“…Sjogren & Sundler. 1983;Dail, McGuffee, Minorsky & Little, 1987), or only minor (Saenz de Tejada, Blanco, Goldstein, Azadzoi, de las Morenas, Krane & Cohen, 1988) inhibitory effects on relaxations induced by electrical field stimulation, and the fact that atropine was without effect on erections provoked by visual stimulation or by local vibration (WN'agner, 1981), favours the occurrence of a non-adrenergic. non-cholinergic (NANC) dilator substance.…”

Expression of α1 adrenoceptor subtypes in rat corpus cavernosum

“…11 Rat corpus cavernosum strips contract in a dose-dependant manner in the presence of noradrenaline. 12 Experimental results therefore suggest that the sympathetic innervation of the penis exerts its antierectile effect through the release of norepinephrine. Furthermore a1 adrenoceptor subtypes has been evidenced in rat vas deferens.…”

“…12,41 In vitro, rat corpus cavernosum strips contract in the presence of noradrenaline. 11 In anesthetized rats, intracavernosal injection of phenylephrine decrease the penile pressure increase elicited by cavernous nerve stimulation.…”