Abstract: Objective To investigate the effect of minocycline on hyperpolarization-activated current (Ih) in the substantia
gelatinosa (SG) neurons in rat spinal dorsal horn. Methods In vitro spinal cord transverse slices were prepared from
3-5-week-old male Sprague-Dawley rats. Using whole-cell patch clamp technique, Ih currents were recorded before and after
bath application of minocycline (1-300 μmol/L) to the SG neurons. Results Ih currents were observed in nearly 50% of the
recorded neurons, and were blocked by Ih blocker CsCl and ZD7288. Minocycline rapidly and reversibly reduced the
amplitude of Ih and decreased the current density in a concentration-dependent manner with an IC50 of 34 μmol/L. Conclusion
Minocycline suppresses the excitability of SG neurons through inhibiting the amplitude and current density of Ih and thereby
contributes to pain modulation.