The effects on penile volume of nerve stimulations and drugs injected into the systemic circulation were studied plethysmographically. Dilator responses at selective perfusion of the penile artery were studied by measuring the perfusion pressure. The main results and conclusions are: The penis has an adrenergic vasoconstrictor supply coming from the sacrococcygeal parts of the sympathetic chains. A very low (0.2 Hz) vasomotor tone keeps the penis relaxed. If this tone is interrupted the penis will protrude but autoregulation will soon take over and eventually produce hyperinvolution of the penis. Two vasodilator paths, both with pelvic ganglionic relays, were found. 1) The pelvic parasympathetic nerves, probably having mainly non-cholinergic postganglionic neurons and operating quite effectively at low frequencies. 2) The sympathetic hypogastric nerves, presumably having at least partly cholinergic postganglionic neurons which, apart from muscarinic dilation of minute inflow resistance vessels to the erectile tissue, may also work by suppression of excitatory adrenergic neurotransmission. The pelvic and hypogastric vasodilator outflows work synergistically. The vasoconstrictor nerves are very strong and efficient antagonists of the vasodilator nerves.

Spontaneous rhythmic activity, responses to drugs and effects of field stimulation of nerves of the retractor penis (rp) and/or corpus cavernosum urethrae (ccu) of macaque, rabbit, guinea-pig, rat, dog, cat, horse, boar, elk, bull, ram and goat, as well as of the penile artery (pa) of bull were studied. A basic property of all these muscles was automaticity. Their responses to 5-hydroxytryptamine, histamine, adenosine triphosphate, prostaglandins E1, E2, AND F2alpha, oxytocin, vasopressin, substance P, bradykinin and angiotensin exhibited considerable species variations. Their excitatory innervation seems to be adrenergic. They also have an inhibitory innervation. In spite of comprehensive pharmacological analysis the inhibitory mediator remains obscure. The frequency--response relationship to inhibitory nerve stimulation was characterized by a rapidly achieved maximum at low frequencies, indicating high efficiency of the neuroeffector unit.

Ropivacaine is a new local anaesthetic agent. Previous animal studies have indicated that vasoconstrictor effects are elicited by ropivacaine in vitro and subcutaneously and that it produces blanching of the skin if injected subcutaneously in humans. Lidocaine is a widely used local anaesthetic reported to exert a biphasic effect on the microvasculature with contraction at low concentrations and relaxation at high concentrations. There is a need for pharmacologic tools able to counteract local arterial vasoconstriction. In this study, the contractile effect of ropivacaine and lidocaine were investigated in vitro on isolated human arteries. Experiments were performed on 43 internal mammary artery (IMA) rings obtained from 22 patients and on 14 radial artery (RA) rings from 7 patients. The rings were mounted in organ baths and isometric contractile activity was measured. Experiments were conducted by cumulative adding ropivacaine or lidocaine (1.5 x 10(-5) M; 4.5 x 10(-5) M; 1.5 x 10(-4) M; 4.5 x 10(-4) M; 1.5 x 10(-3) M; 4.5 x 10(-3) M; 1.5 x 10(-2) M) to the organ baths. The endothelium was mechanically removed in 19 IMA rings and in 9 RA rings. Ropivacaine and lidocaine produced a biphasic response with contraction at low concentrations (1.5 x 10(-5)-1.5 x 10(-3) M) and release of the maximal contraction at higher concentrations. No statistically significant differences in contractile or relaxing effects were seen between the two drugs. Removal of the endothelium did not significantly affect contractile activity. In this study of human mammary artery preparations, ropivacaine is not a stronger vasoconstrictor than lidocaine.