Carbachol-regulation of the expression of αi1-subunit of G i and inositol-[l,4,5]-trisphosphate receptor in brain samples obtained from neonatal and adult rats

Abstract

The basal steady-state concentration and the transcription rate of α Gi1-mRNA in neonatal brain were greater than those in adult brain. The T 1 2 values for α Gi1-mRNA in neonatal and adult samples did not differ significantly. This suggests that the resting concentration of α Gi1-mRNA is regulated by its synthesis in brain. The basal steady-state concentration, the transcription rate and the t 1 2 values of [l,4,5]IP 3R-mRNA in neonatal and adult brains did not differ significantly. Carbachol increased the concentration and the transcription rate of α Gi1-mRNA and [1,4,5]IP 3R-mRNA both in neonatal and adult samples. The increase in α Gi1-mRNA concentration was affected by the age of the animals but the increase in [l,4,5]IP 3R-mRNA concentration was not. However, the increase in the TR of α Gi1-mRNA or [l,4,5]IP 3R-mRNA was affected by the age of the animals. In the presence of carbachol, the degradation of mRNA occurred in two phases: a fast-phase with t 1 2 ranging from 1.4 to 1.8 h and a slow phase with t 1 2 ranging from 4 to 7 h. The t 1 2 values were not affected by the age of the animals. This study, therefore, suggests that developmental process down-regulates the expression of α Gi1-mRNA but does not affect the expression of [l,4,5]IP 3R-mRNA in brain. Carbachol increases the steady-state concentration of both α Gi1-mRNA and [l,4,5]IP 3R-mRNA possibly by altering their synthesis and stability in brain.