Nucleobase adenine as a trophic factor acting on Purkinje cells

We examined the influence of nucleobases, nucleosides, nucleotides, and their analogs on rat cerebellar Purkinje cells in primary culture and found that the number of cultured Purkinje cells was greatly increased by the nucleobase adenine. Purkinje cells were cultured for 13 days in vitro in the presence of various reagents, and the resulting cell numbers were counted. As a result, the nucleobase adenine was most effective at increasing the number of Purkinje cells among the reagents tested. In the cultures supplemented with adenine in millimolar concentrations (1-2 mM), the number of Purkinje cells was increased by up to 30 times the number of Purkinje cells in the control. Adenine had no affect on the number of granule cells, and it reduced the number of astrocytes, both of which were cocultured in cerebellar primary cultures. Stimulation of purinoceptors by adenosine and adenosine 5'-triphosphate (ATP) did not result in an increase in the number of Purkinje cells. Furthermore, the adenine effect on Purkinje cells was not related to PKA, as determined with the use of a PKA inhibitor. Our findings suggest that adenine exerts neurotrophic effects that have not been described to date; in particular, the present study demonstrated that adenine increases the number of Purkinje cells by an unknown mechanism.