IN VIVO PATHWAY ANALYSIS FOR THE EFFECT OF HYPERTHYROIDISM ON EJACULATION IN PHARMACOLOGICALLY-INDUCED EJACULATION IN ANAESTHETISED MALE RATS

Abstract

INTRODUCTION AND OBJECTIVE: 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: Sixty male Wistar rats (300-350gr) were used in this study. Subcutaneous injection of L-Thyroxine for 14 days was performed to induce hyperthyroidism in thirty rats. 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 both groups), bilateral pelvic nerve(PNx,n=6 for both groups), bilateral paravertebral sympathetic chain (PSCx,n=6 for both groups) transections, complete spinal transection at the T8-T9 level (n=6 for both groups ) and no peripheral transection (Nonx) was performed for 6 rats in each group. 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, SV phasic contraction(SVPC) frequency, SVPC maximal amplitude and BS EMG area under curve values were higher in hyperthyroid Nonx rats than euthyroid Nonx rats. The time interval between PCA administration and first ejaculation, the time interval between first SVPC and first BS contraction of hyperthyroid Nonx rats were significantly shorter than euthyroid Nonx rats. In hyperthyroid rats bilateral HNx and bilateral PSCx significantly reduced SV tonic pressure ampitude, SVPC frequency and SVPC maximal amplitude. There were no differences in SVPC frequency and SVPC maximal amplitude values for HNx and PSCx between euthyroid and hyperthyroid rats. These values were higher in hyperthyroid PNx rats than euthyroid PNx rats. There were no significant differences between all parameters of emission and expulsion phases of ejaculation for euthyroid and hyperthyroid spinally transected rats. CONCLUSIONS: 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