The effect of hyperthyroidism on pharmacologically-induced ejaculation in anaesthetised rats: in vivo neural pathway analysis

İNTRODUCTİON AND OBJECTİVE: The aim of the current study is to determine the possible effects of hyperthyroidism on ejaculatory pathways in p-Chloroamphethamine(PCA) induced ejaculation in anaesthetised male rats.METHODS: 96 male Wistar rats (300-350gr) were used in this study. The study consist of 2 major groups: spinal intact and spinal transection groups. Each group were divided to hyperthyroid and euthyroid groups. Subcutaneous injection of L-Thyroxine for 14 days was performed to induce hyperthyroidism in hyperthyroid group and 0,9%NaCl injection to euthyroid group. At the end of injection period thyroid hormone status were evaluated by serum TSH measurements in all rats. Under intraperitoneally(i.p.) urethane anaesthesia; euthyroid and hyperthyroid rats underwent bilateral hipogastric nerve(HNx,n=6 for each groups), bilateral pelvic nerve(PNx,n=6 for each groups), bilateral paravertebral sympathetic chain (PSCx,n=6 for each groups) transections, and no peripheral transection was performed for 6 rats in each group (Nonx). Acute spinal cord transection was performed at the T8-9 level. After performing seminal vesicle (SV) catheterization and bulbospongiosus (BS) muscle dissection for SV pressure measuring and BS electromyographic (EMG) recordings we induced ejaculation with i.p. administration of 5 mg/kg PCA. Ejaculatory responses were recorded before and 30 min after PCA administration.RESULTS: After PCA administration SV pressure tonic amplitude(p<0,05), SV phasic contraction frequency(p<0,01), SV phasic contraction maximal amplitude(p<0,05) and BS EMG area under curve(AUC) values(p<0,05) were higher in hyperthyroid Nonx rats than euthyroid Nonx rats. The time interval between PCA administration and first ejaculation(p<0,01), the time interval between first SV phasic contraction and first BS contraction(p<0,01) of hyperthyroid Nonx rats were significantly shorter than euthyroid Nonx rats. In hyperthyroid and euthyroid rats bilateral HNx and bilateral PSCx significantly reduced SV phasic contractions frequency and SV phasic contraction maximal amplitude(p<0,001). There were no differences in SV frequency and SV maximal amplitude values for HNx and PSCx between euthyroid and hyperthyroid rats. These values were higher in hyperthyroid PNx rats than euthyroid PNx rats(p<0,05). BS muscle EMG activity?s AUC value was higher in hyperthryoid rats in all periferic transection subgroups(p<0,05). There were no significant differences between all parameters of emission and expulsion phases of ejaculation for euthyroid and hyperthyroid spinally transected ratsCONCLUSION: In this study we confirmed the recent data that hyperthyroidism effects both the emission and expulsion phases of ejaculation. The effect of hyperthyroidism on emission phase is probably by sympathetic pathways. However the overall effect of hyperthyroidism on ejaculation may take place in the central nervous system above T8 level.Keywords: Hyperthyroidism, ejaculation, periferic nerve transection, PCA