Plasma levels of cavernous and systemic norepinephrine and epinephrine in men during different phases of penile erection.
OBJECTIVE
Knowledge of the functional anatomy, hemodynamics, neurophysiology and pharmacology of penile erection has improved tremendously during the last 2 decades. However, only few in vivo studies on human peripheral neurotransmission have been carried out up until now. Therefore, we conducted a study to examine plasma levels of catecholamines norepinephrine (NE) and epinephrine (E) in the peripheral and cavernous blood of healthy men during penile flaccidity and in different phases of erection.


METHODS
Blood samples were drawn simultaneously from the corpus cavernosum (CC) and the cubital vein (P) in 53 healthy volunteers with normal erectile function, in four different functional states of the cavernous erectile tissue (flaccidity = 1, tumescence = 2, rigidity = 3, detumescence = 4). Penile erections were induced by audiovisual and tactile stimulation and the plasma concentrations of NE and E were determined by means of a radioimmunoassay (RIA).


RESULTS
A significant (p <0.001) reduction of NE in CC plasma was found from flaccidity (362 + or - 173 pg./ml.) to rigidity (248 + or - 122 pg./ml.), followed by an increase in the detumescence phase (336 + or - 199 pg./ml.), (p <0.001). In contrast, changes in NE levels in the peripheral plasma were less pronounced from 1P (202 + or - 102 pg./ml.) to 3P (229 + or - 118 pg./ml.), (p = 0.006) and from 3P to 4P (222 + or - 127 pg./ml.), respectively (p = 0.370). The most pronounced increase in cavernous E levels were observed from flaccidity (47 + or - 41 pg. /ml.) to tumescence (130 + or - 106 pg./ml.) (p <0.001). Cavernous E levels dropped significantly from 113 + or - 67 pg./ml. during rigidity to 76 + or - 57 pg./ml. + or - during detumescence (p <0.001). The course of peripheral plasma levels of E was similar to that in the cavernous blood. Mean peripheral E level was 69 + or - 55 pg./ml. in the state of penile flaccidity, reaching 98 + or - 78 pg./ml. in tumescence and 82 + or - 64 pg./ml. in rigidity (p <0.001), respectively, and finally decreasing to 62 + or - 46 pg./ml. in detumescence.


CONCLUSIONS
Penile erection, based on the relaxation of cavernous and arterial smooth muscle, is accompanied by a significant reduction of NE in cavernous blood, while E levels rose in peripheral and cavernous blood during developing erection.
Becker
A J
AJ
Departments of Urology, Nuclear Medicine, and Psychological Medicine, Hannover Medical School, Hannover, Germany.
Uckert
S
S
Stief
C G
CG
Truss
M C
MC
Machtens
S
S
Scheller
F
F
Knapp
W H
WH
Hartmann
U
U
Jonas
U
U
D000328:Adult; D004837:Epinephrine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009638:Norepinephrine / Q000097:blood*; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000098:blood supply*
D009638:Norepinephrine; D004837:Epinephrine