title: Electrical and mechanical responses of the bovine retractor penis to nerve stimulation and to drugs.
abstract: The responses of the bovine retractor penis muscle to field stimulation of intramural nerves in vitro was investigated using micro-electrode and extracellular (sucrose gap) techniques. In the absence of tone single pulses or trains of stimuli (1-50 Hz 0.1-0.5 m.sec) produced e.j.p.s and a decrease in membrane resistance; spike potentials were not observed. E.j.p.s often small in amplitude (3-5 mV to single pulse) and accompanied by contractions in almost all preparations were noradrenergic, abolished by guanethidine (1-3 x 10(-5) M) and tetrodotoxin (3.5 x 10(-6) M) but not by prazosin (0.05 - 1.4 x 10(-6) M). Prazosin abolished the depolarization and contraction produced by added NA (0.02 - 2 x 10(-8) moles). TEA (10(-2) M) depolarized the membrane and initiated spontaneous activity; e.j.p.s and contractions were enhanced and prolonged but no spikes were observed. Atropine (0.5 x 10(-6) M) increased and physostigimine (1-5 x 10(-6) M) decreased e.j.p.s and contractions indicating a cholinergic regulatory component in the release of the excitatory transmitter. In the presence of tone, nerve stimulation produced i.j.p.s. and relaxations which were unaffected by apamin (5 x 10(-7) M), atropine (3 x 10(-6) M), guanethidine (3 x 10(-5) M), phentolamine (5 x 10(-6) M) and propranolol (4 x 10(-6) M) but were abolished by tetrodotoxin (3.5 x 10(-7) M) suggesting their mediation by non-adrenergic non-cholinergic (NANC) nerves. Sodium nitroprusside (10(-10) - 10(-8) moles), which increases cyclic GMP, also hyperpolarized the membrane and relaxed the BRP. Those responses and those to inhibitory nerve stimulation were antagonized by oxyhaemoglobin which inhibits guanylate cyclase. 2-O-propoxyphenyl-8-azapurin-6-one (M & B 22948 3-9 x 10(-6) M) which inhibits cGMP-specific phosphodiesterase, enhanced the relaxation but not the i.j.p. TEA (10(-2) M) initially depolarized the membrane potential and raised tone. In the sucrose gap inhibitory potentials were abolished; the mechanical relaxation was not and a small contractile component emerged. Electrical and mechanical inhibitory components in the bovine retractor penis may not be correlated.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002417:Cattle; D006152:Cyclic GMP / Q000502:physiology; D004558:Electric Stimulation; D004594:Electrophysiology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D010413:Penis / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D010830:Physostigmine / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D013757:Tetraethylammonium Compounds; D001285:Atropine; D010830:Physostigmine; D006152:Cyclic GMP