Comparisons of neurotransmitter concentrations in the synaptosomal preparation of the normotensive and hypertensive rat urinary bladder

Synaptosome-rich fractions were prepared from tissue homogenate of the urinary bladder of the spontaneously hypertensive rat and normotensive Wistar-Kyoto rat by differential centrifugation (1000 x g, 17,000 x g and 100,000 x g) with discontinuous sucrose gradient. Synaptosomal acetylcholine, norepinephrine, epinephrine and dopamine were measured by the method of high-performance liquid chromatography. The respective neurotransmitter concentrations for the normotensive rats were 300.4 ± 30.1, 962.8 ± 58.5, 617.3 ± 59.8, and 1354.8 ± 144.2 pmol/mg synaptosomal protein. For the hypertensive rats, the acetylcholine concentration (203.8 ± 23.0 pmol/mg protein) was significantly lower (P < 0.05), while the norepinephrine, epinephrine and dopamine concentrations (1459.0 ± 180.3, 971.3 ± 62.2, and 2161.0 ± 243.4 pmol/mg protein, respectively) were significantly higher (P < 0.05 for all) than those of the normotensive rats. In conclusion, it has been demonstrated that the vesicle-bound catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in hypertensive rats. On the contrary, the synaptosomal acetylcholine concentration was significantly decreased. These findings are suggestive of increased sympathetic innervation and decreased parasympathetic innervation in the urinary bladder of the spontaneously hypertensive rat.