Influence of temperature on activity of the isolated whole bladder preparation of neonatal and adult rats

The temperature sensitivity of in vitro whole bladder preparations from neo natal and adult rats with or without chronic partial urethral obstruction w as investigated. After the bladder was filled to a volume eliciting isovolu metric contractions, temperature was changed between 19 and 38 degrees C. I n all preparations, higher temperatures were associated with higher frequen cies of spontaneous intravesical pressure waves (IVPW). In 1- to 2-wk-old n eonates, IVPW amplitude increased as the temperature increased; however, in older neonates and normal adults, the opposite occurred. The transition pe riod was at 3 wk of age when bladder volume also markedly increased. At thi s age as well as in adult rats with outlet obstruction, changing temperatur e had little influence on the amplitude of IVPW. Thus obstructed outlet bla dders and 3-wk-old bladders had similar properties. It is concluded that th e properties of bladder muscle are changed during postnatal maturation and that in 3-wk-old rats, when brain control of voiding is emerging, micturiti on is abnormal, leading to obstructive changes in bladder muscle.