A functional study was done to examine a possible role of calcitonin-gene-related peptide in human penile erection and its possible therapeutic applications for patients with erectile dysfunction. In the determination of an effective dosage, 5 ng. (2 patients), 50 ng. (2 patients), 500 ng. (4 patients), 5 micrograms (4 patients) and 25 micrograms (7 patients) were injected intracavernously, and pulse and blood pressure were monitored. Arterial inflow was measured by Doppler sonography, smooth muscle relaxation was determined by the analysis of cavernous electrical activity and cavernous outflow occlusion was recorded by cavernosometry. In 12 patients the erectile response of prostaglandin E1 was compared to the response of an equal (6 patients) or decreased dose of prostaglandin E1 combined with an equal weight of calcitonin-gene-related peptide. In 14 patients the erectile response to the combination of calcitonin-gene-related peptide and prostaglandin E1 was compared to the response of prostaglandin E1 alone, and with a combination of 15 mg./ml. papaverine and 0.5 mg./ml. phentolamine. Calcitonin-gene-related peptide induced an increase in the penile arterial inflow, cavernous smooth muscle relaxation and cavernous outflow occlusion. Histochemical results indicated nerve fibers positive for calcitonin-gene-related peptide within the cavernous bodies. A dose-dependent erectile response to calcitonin-gene-related peptide was observed at doses of 500 ng. to 25 micrograms. Systemic side effects were first observed at a dose of 25 micrograms in 2 of 7 patients. The combination of calcitonin-gene-related peptide and prostaglandin E1 was more effective in inducing a full erection than either prostaglandin E1 alone or the combination of papaverine and phentolamine. Pain was reported in 4% of the patients who received the combination of calcitonin-gene-related peptide and prostaglandin E1, whereas 42% of those who received prostaglandin E1 alone reported pain. Our results suggest that calcitonin-gene-related peptide may be a possible neurotransmitter for penile erection. A combination of calcitonin-gene-related peptide and prostaglandin E1 seems to be an effective alternative combination in the treatment of impotence.
Summary. The aim of our study was to examine the cavernous smooth-muscle electric activity in normal and impotent patients as well as in those with (presumably) welldefined neurologic lesions. Single potential analysis of cavernous electric activity (SPACE) was done in 112 consecutive impotent patients, 34 normal patients, and 19 patients referred especially for SPACE. In the normal patients, similar potentials with a mean duration of 9.5 s, a mean amplitude of 153 ~V and a mean polyphasity of 8.5 were recorded (cutoff frequencies, 2-2000 Hz), with cutoff frequencies set at 0.5 -500 Hz, the mean duration was 12.8 s, amplitude was 444 ktV and the mean polyphasity was 13.8 Upper spinal cord lesions showed potentials of long duration as well as whips and bursts. Patients with lower motor-neuron lesions showed either short potentials of high amplitude or potentials of small amplitude. In 49% of the impotent patients, abnormal SPACE was found. Our results suggest that SPACE is a reproducible and minimally invasive method for the diagnosis of autonomic neurogenic impotence.
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