ONTOGENETIC DEVELOPMENT OF ADENYL CYCLASE AND PHOSPHODIESTERASE IN RAT BRAIN

Abstract— The activities of adenyl cyclase and phosphodiesterase were determined in homogenates of cerebrum, cerebellum and brain stem of rats of 1 day to 9 weeks of postnatal age. The activity of cerebral and brain stem adenyl cyclase measured either in the absence or presence of sodium fluoride increased rapidly for 2 weeks, reached at 20 days a maximum about three times (brain stem) or six times (cerebrum) that seen on day 1 and then declined slightly during the next several weeks. In contrast, activity of cerebrellar adenyl cyclase increased more slowly and reached a maximum at about 32 days. Activity of phosphodiesterase in cerebrum and brain stem increased several-fold during brain maturation; however, enzymic activity in the cerebellum decreased during the entire 9 week period.
In the pineal gland, adenyl cyclase activity measured in the absence of norepinephrine or sodium fluoride did not change significantly with age. However, enzymic activity measured in the presence of these agents increased with the age of the rat. Bilateral removal of the superior cervical ganglia at 1 day of age is known to arrest the sympathetic innervation of the pineal gland but did not prevent the development of this adenyl cyclase system activated by catecholamines or fluoride.