Action potential threshold of wide dynamic range neurons in rat spinal dorsal horn evoked by manual acupuncture at ST36

• ST36 of six rats is acupunctured with three different frequencies.
• Evoked spikes in wide dynamic range neurons in spinal dorsal horn are recorded.
• The threshold voltage of the action potentials is dynamic.
• The broad variations in spike threshold are robust to acupuncture frequency.
• The spike threshold is inversely related to the rate of rise of membrane potential.

This paper investigates the dynamic of action potential initiation in the wide dynamic range (WDR) neurons in spinal dorsal horn of rats evoked by manual acupuncture at ST36 with three different stimulation frequencies. It is observed that the voltage threshold for action potential initiation in WDR neurons is dynamic and varies over a wide range of membrane potential. The broad variations in spike threshold are robust to the acupuncture frequency. It is also shown that the spike threshold is very sensitive to the maximal rate of rise of the action potential upstroke, and there is an obviously inverse relation between them. Our study provides a new perspective on the analysis of acupuncture-evoked signals. The findings could help to interpret how the individual spike evoked by manual acupuncture is generated in WDR neurons, which may contribute to uncover how acupuncture signals are encoded in its afferent neural pathway.