Evaluation of the effects and mechanisms of action of glufosinate, an organophosphate insecticide, on striatal dopamine release by using in vivo microdialysis in freely moving rats

The purpose of the present work was to assess the effects of glufosinate ammonium (GLA), an aminoacid structurally related to glutamate, on in vivo dopamine (DA) release from rat striatum, using brain microdialysis coupled to HPLC-EC. Intrastriatal administration of GLA produced significant concentration-dependent increases in DA levels. At least two mechanisms can be proposed to explain these increases: GLA could be inducing DA release from synaptic vesicles or producing an inhibition of DA transporter (DAT). Thus, we investigated the effects of GLA under Ca++-free condition, and after pretreatment with reserpine and TTX. It was observed that the pretreatment with Ca++-free Ringer, reserpine or TTX significantly reduced the DA release induced by GLA. Coinfusion of GLA and nomifensine shows that the GLA-induced DA release did not involve the DAT. These results show that GLA-induced striatal DA release is probably mediated by an exocytotic-, Ca++-, action potential-dependent mechanism, being independent of DAT.