Minoru Miyazato

Aims We investigated the changes in bladder and urethral function after cerebral infarction (CI) and the influence of tramadol on these functions. Methods Twenty‐eight female Sprague Dawley rats were divided into normal and CI groups. In the awake condition, metabolic cage study and blood pressure were evaluated. Under urethane anesthesia, the intravenous effect of tramadol (0.01–1 mg/kg), which has both µ‐opioid receptor stimulation and inhibition of norepinephrine and serotonin reuptake, on continuous cystometry, and simultaneous measurements of bladder and urethral perfusion pressure (UPP) were recorded. Infarcted lesions were examined by staining with triphenyltetrazolium chloride, a marker of mitochondrial enzyme activity. Results CI rats showed impaired sympathetic activity with Horner's syndrome and lower blood pressure. In metabolic cage study, urinary frequency during the dark phase was increased in CI rats. On bladder activity, in CI rats, the baseline pressure threshold for inducing bladder contractions was significantly lower ( p < 0.01), and the intercontraction interval was prolonged after tramadol administration. On urethral activity, the baseline UPP was significantly lower in CI rats than in normal rats and it did not change after tramadol administration. Residual urine rate was significantly increased in normal rats, but not in CI rats. CI rats showed brain infarction including the cortex and hypothalamus, which is a center of the autonomic nervous system. Conclusions CI‐induced ischemic brain damage results in impairment of both bladder and urethral functions, in addition to decreased sympathetic activity. Bladder overactivity after CI can be improved by tramadol; however, urethral activity cannot be improved by it.