Objective To observe changes of electrical activities of wide dynamic neurons(WDR)in the lumbar spinal cord after electroacupuncture(EA)stimulation of"Zusanli"(ST 36)during colorectal distension in rats

so as to analyze alternations of acupoint's functions under pathological conditions.Methods Experiments were performed in male Sprague-Dawley rats.Visceral nociceptive information input was generated by colorectal distension(CRD).Extracellular discharges of WDR neurons in the dorsal horns of L1-3spinal cord were recorded using glass micropipettes and a microelectrode amplifier.EA stimulation(15Hz

1

4

7

10mA)was applied to ipsilateral"Zusanli"(ST 36)area.Results A total of 40 neurons were recorded in the present study.Under no CRD conditions

the firing rates of WDR neurons were significantly increased by(18.12±13.56)%(1mA)

(152.38±36.19)%(4mA)

(231.21±49.74)%(7mA)and(331.54±61.89)%(10mA)respectively after EA stimulation of ST 36.Under CRD conditions

the firing rates of these WDR neurons were increased by(226.78±39.59)%(1mA)

(282.80±47.54)%(4mA)

(343.06±58.35)%(7mA)

and(338.62±80.04)%(10mA)respectively after EA stimulation.It showed a considerablely increased sensitivity of electrical activities of WDR neurons to EA stimulation during CRD nociceptive stimulation.Conclusion Colorectal distension(visceral nociceptive stimulation)can strengthen the sensitivity of acupoint-EA stimulation-induced increase of firing rates of WDR neurons in the dorsal horns of the lumbar spinal cord in rats

suggesting apotentiation of the acupoint action under visceral nociceptive signal inputs.