Granulocyte macrophage colony-stimulating factor regulates activity of the nervous system.

Objectives: The peripheral administration of granulocyte macrophage colony-stimulating factor (GM-CSF), widely used for the treatment of cytopenias, is often associated with neurological effects [Lieschke et al., N Engl J Med 1992;327:28-34]. This cytokine has recently been reported to affect neurotransmitter metabolism in the nervous system [Bianchi, Neuroreport 1997;8:3587-3590]. To further investigate the neuromodulatory effect of GM-CSF we studied the influence of GM-CSF on the efferent electric activity in the splenic nerve and the integral neuronal activity in medullary gigantocellular reticular formation (MGRF) in rats.

Methods: Anaesthetized (sodium thiopental 70 mg/kg, i.p.) Wistar rats were injected subcutaneously with 1 microg/kg of hr GM-CSF. Efferent electric activity in the splenic nerve and integral electric activity in MGRF were analyzed. The effectiveness of the applied dose of GM-CSF was verified by determining the elevation of the white blood cell count in peripheral blood 60 min after injection.

Results: We found that GM-CSF increases efferent electric activity in the splenic nerve and decreases that of MGRF as is evident by the frequency of electric discharges. The latency of both effects was 5-15 min.

Conclusions: This data support the view that GM-CSF exerts a neuromodulatory effect and may provide a new link of neuroimmune communication.