Retrograde SA recorded from the dorsal root in rats with MIA-OA. (A) Preparation design for recording efferent activity from the L4 dorsal triggered by afferent activity induced by L3 DRG stimulation using the GFS electrode. (B) Sample traces show evoked retrograde firing in response to single afferent impulse (0.4mA, 02ms, 0.2Hz, red arrow, which is blocked by TTX at the dorsal root entry zone (C), confirming it origin from the dorsal horn. SA was also recorded, which was similarly sensitive to TTX (D). MIA-OA increased the incidence of retrograde SA (E). These recordings were from 5 rats with saline injection and n=5 rats with injection of MIA. ***P<0.001 by Chi-square comparisons.