Cochlear blood flow in relation to age in normotensive and spontaneously hypertensive rats.

Cochlear blood flow was studied with the microsphere method in young and old normotensive and spontaneously hypertensive rats. The young animals were 3-6 months old and the old ones 18-24 months. The cochlear blood flow in young rats was 1.64 microliter/min/cochlea for the normotensive and 1.51 for the spontaneously hypertensive rats. In the old rats, the cochlear blood flow rates were 1.40 and 1.29 microliter/min/cochlea, respectively. The differences were not significant between the age groups, nor between the normotensive and spontaneously hypertensive rats. However, there was a tendency towards lower cochlear blood flow with increasing age, especially among the spontaneously hypertensive rats. The difference between young normotensive and old spontaneously hypertensive rats was significant (p less than 0.05). The group of old hypertensive rats was also the only one with evident morphological changes in the organ of Corti.