An Ex Vivo Evaluation of Regulatory Role of Biogenic Amines in Rat Seminal Vesicle after Pharmacological Manipulation

We studied the neural regulation of seminal vesicles (SV) by determining the changes of intraluminal pressure of rat SV in response to an electric stimulation of the lesser splanchnic nerve (LSN). After pharmacological manipulation with neurotoxin, the contents of monoamines and their metabolites in SV were estimated. In rats receiving electric stimulation of the LSN, an increase of intraluminal pressure was obtained with a reduction of the serotonergic turnover rate in SV. An intraperitoneal injection of DSP-4 ( 100 mg/kg), the noradrenergic neurotoxin, into rats decreased the level of norepinephrine (NE) in SV significantly but did not influence this functional response . Also, the intraluminal pressure was lowered by an intrathecal injection of 6-OHDA (20 mu g/rat) to denervate spinal monoaminergic nerves in rats although the contents of monoamines in SV were not changed. This indicates that noradrenergic neurotransmission appears unimportant in this regulation. The lowering of intraluminal pressure in rats by 6-OHDA is mainly related to an attenuation of dopaminergic neuroregulation from the decrease of turnover rate of DA. Otherwise, an intrathecal injection of 5,7-DHT (60 mu g/rat) to abolish spinal serotonergic nerves did not influence the level of monoamines in SV but increased the intraluminal pressure indicating an involvement of inhibitory regulation from spinal serotonergic pathway. These results suggest that contraction by electric stimulation of the LSN in Wistar rat SV is mainly regulated by the dopaminergic nervous pathway and an inhibitory regulation of the serotonergic nervous pathway from spinal cord while the noradrenergic nervous system seems unimportant for this regulation. (C) 1998 Elsevier Science Inc