Subcellular distribution and postnatal development of cholinergic marker proteins in the striatum of rat

The distribution of muscarinic cholinergic receptors, choline acetyl-transferase and acetylcholinesterase activities were measured in subcellular fractions of the rat striatum on the 5th and 15th days postnatally and in adulthood. The receptor density in the striatum of 5 and 15-day-old rats was 15%, respectively, of the adult value. Similar increases of the receptors could be detected in the synaptosomal and microsomal fractions in the postnatal life of rat. The activity of choline acetyltransferase on the same days was 15% and 28%. In the subcellular fractions, the enzyme activity was the highest in the microsomal fraction on both the 5th and 15th days postnatally. The activity of acetylcholinesterase in the homogenate was 6% of the adult value in the 5-day-old rat striatum, while in the synaptosomal fraction it was 11% and 47% of the adult value on the 5th and 15th days, respectively. Our results show that the development of the muscarinic cholinergic receptors precedes that of the two cholinergic enzymes in both 5 and 15-day-old rat striatum. This may suggest an early perikaryonal synthesis and the fast translocation of receptors to the axon terminals during ontogenetic development.