To explore the changes of the endogenous phosphorylation of brainstem mitochondrial and synaptosomal proteins in adult hens dosed with tri-o-cresyl phosphate (TOCP) following the development of organophosphate-induced delayed neurotoxicity (OPIDN). Verapamil (7mg/(kgday), i.m.) was given for 4 days. A dose of TOCP (750mg/kg, p.o.) was administrated in second day after verapamil. Phosphorylation of the proteins from brainstem mitochondria and synaptosomes was assayed in vitro by using [γ-(32)P]ATP as phosphate donor. Radiolabeled proteins were separated by SDS-PAGE and visualized by autoradiography. The results showed that TOCP administration enhanced the phosphorylation of the cell organelle proteins (mitochondria: 60, 55, 45, and 20kDa; synaptosomes: 65, 60, and 20kDa), while verapamil abolished the enhancement induced by TOCP. Additionally, the reaction for the phosphorylation is catalyzed by the calcium/calmodulin protein kinase. Therefore, TOCP can enhance the phosphorylation of the brainstem mitochondrial and synaptosomal proteins from the hens with OPIDN; however, protection from the enhancement of the phosphorylation should be involved in the mechanisms of the amelioration of TOCP-induced delayed neurotoxicity by verapamil.