Postnatal development of calmodulin and calmodulin‐dependent phosphodiesterase in different regions of the rat central nervous system

We have studied the concentration of calmodulin and phosphodiesterase (cAMP high Km) in five different parts of the rat central nervous system (hemispheres, cerebellum, diencephalon, brain stem and spinal cord) during postnatal development (5, 10, 15, 20, 30 and 45 days after birth). The concentration of the enzyme and its regulatory protein were independent, so that no correlation could be established between them. In most structures, calmodulin concentration tended to decrease with age, while phosphodiesterase increased or remained at similar values during the time studied. The calmodulin inhibitor trifluoperazine, inhibited phosphodiesterase activity to different degrees, depending on the structure, and age. Hemispheres, diencephalon and brain stem showed maximal inhibition (approximately 95-65% of control). In these structures, inhibition was higher in older animals. By contrast, cerebellum and spinal cord PDE was less inhibited by trifluoperazine (65-50% of control), and inhibition was independent of age. The validation of a method for both calmodulin and phosphodiesterase assay, using a modification of established methods, is also reported.