Regulation of peripheral-type benzodiazepine receptors in cultured astrocytes by monoamine and amino acid neurotransmitters.

Exposure of primary cultured astrocytes for 3 days to 1 microM of either dopamine, serotonin or norepinephrine resulted in upregulation (25-34% increase in Bmax) of the peripheral-type benzodiazepine receptors (PBRs) labeled with [3H]Ro5-4864. A similar treatment with gamma-aminobutyric acid [GABA] caused a 2-fold increase in the affinity (Kd) of [3H]Ro5-4864. The monoamines tested and GABA had no effect on the binding parameters of [3H]PK 11195, another selective PBR ligand. The present study indicates that Ro5-4864 binding sites are susceptible to regulation by specific neurotransmitters and provides further evidence for the distinction between Ro5-4864 and PK 11195 binding sites of the PBRs in cultured astrocytes.