Opposite modulation of glutamate uptake by nicotine in cultured astrocytes with/without cAMP treatment

Cultured cerebellar astrocytes were exposed to nicotine with or without dibutyryl cAMP (dBcAMP) for 2 to 10 days in situ in order to determine the effects of nicotine exposure on glutamate uptake in differently conditioned astrocytes. After acute nicotine exposure, glutamate uptake was lower and higher in the naive and the preconditioned astrocytes, respectively. After subacute nicotine exposure, the inhibitory effect of L-trans-pyrollidine-2,4-dicarboxylic acid (PDC) on the glutamate uptake in the naive and the conditioned cells was decreased and increased, and the IC50's for PDC were higher and lower, respectively. In addition, glutamine synthetase activity after subacute nicotine exposure was lower in the naive and higher in the conditioned astrocytes; the change in Na+/K+ ATPase activity was the opposite to that in glutamine synthetase activity. These results suggest that nicotine modulates the characteristics of glial glutamate transporters and glutamine synthetase activity in astrocytes. Furthermore, nicotine might differently affect the state of glial cells during development.