This study aimed at assessing the effects of diazoxon (DZO), a major metabolite of the insecticide diazinon (DZ), on key cytoskeletal proteins in differentiating N2a neuroblastoma cells. Initial experiments established that sublethal concentrations of 1, 5 and 10 µM DZO produced profound inhibition of neurite outgrowth. Densitometric scanning of probed immunoblots of N2a cell lysates demonstrated that DZO had no effect on total beta-tubulin levels. However, probing with a monoclonal antibody that recognised specifically the betaIII-tubulin isotype revealed that 10 µM DZO induced a significant reduction in the levels of this particular form. Levels of polyglutamylated tubulin were not altered. Exposure to 10 µM DZO also decreased the expression of microtubule-associated protein 1B (MAP 1B). However, DZO had no effect on the expression of MAP tau. DZO also failed to affect the levels neurofilament light (NFL) and neurofilament medium (NFM) chain levels. Indirect immunofluorescence demonstrated that the staining of neurites in treated cells was weaker than in the controls for betaIII-tubulin. In conclusion, DZO disrupts the microtubule (MT) network affecting the expression and distribution of two specific MT proteins known to be important in neuritogenesis. DZO may contribute to the developmental neurotoxicity seen following exposure to DZ. PUBLICATION ABSTRACT