The Response Of Primary Sensory Neuron To Acupuncture And Moxibustion-like Stimulation At Different Designed Parameters In Rats

Background:Acupuncture and moxibustion can cure disease mainly via activating the nervous system.And peripheral nerve is an important pathway for immediate signal input of acupuncture and moxibustion.Kagitani's research team has proven that manual acupuncture at ST36 can activate ?,?,?,? somatic afferent nerves,and another researcher found the effect of acupuncture is inhibited with locally injecting anaesthetic lidocaine in subcutaneous tissue.Besides,numerous studies have shown that different intensities of acupuncture and moxibustion can lead to various effects,though act on the same acupoint.The relationship between intensities of electroacupuncture and nerve activation has been observed in spinal dorsal horn wide dynamic range(WDR)neurons,together with the relationship between different temperature of moxibustion and activation of subnucleus reticulanis donsalis(SRD)neurons have been studied.However,rare scholars study on how the signals of acupuncture or moxibustion stimulation are transmitted along the peripheral primary nervous system and what is the most appropriate stimulus parameter of acupuncture and moxibustion to activate the nervous systemObjective:To observe the response ability and response gradient of primary sensory neurons under different acupuncture(moxibustion)intervention methods and intervention intensities,and to clarify the coding characteristics and dose-effect relationship of various types of neurons related to acupuncture(moxibustion)effects.Methods:Female SD rats weighing 200-250g were used.Dorsal root ganglion electrophysiological recording and dorsal root recording were adopted in vivo of L4/5 nerve on the left side where nerve impulses elicited by acupuncture or moxibustion.Results:(1)In this experiment,34 A? neurons,12A? neurons,47 C-HTMR neurons,and 18 C-LTMR neurons were recorded,and all four types of neurons could be activated by needle-like stimulation.(2)The activation degree of these four types of neurons is related to the stimulation intensity.With the increase of mechanical stimulation intensity,the number of neurons firing per second also increases,but when the stimulation reaches a certain intensity,the neuronal firing rate tends to be stable.The firing rate of A? neurons was stable at(12.78±2.78)?(15.59± 2.04)Hz within 10 mN?60 mN stimulation,showing a significant plateau.The response ratio of A? neurons reached a plateau at 60 mN,and the firing rates of 60 mN,100 mN and 260 mN stimuli were 7.52±2.98,7.44±2.62 and 7.66±1.80 Hz,respectively.The firing rate of C-LTMR neurons tended to be stable and maintained at about 10 Hz after the stimulation intensity reached 20 mN.The C-HTMR neurons discharge tended to be stable within the stimulation intensity of 100 mN?260 mN,with firing rates between 7.30±1.53 and 7.39±2.02 Hz.(3)For the firing of primary sensory neurons evoked by different acupuncture twisting angles,the trends of these four types of neurons were more consistent.Whether it is A?,A?,C-HTMR or C-LTMR,the number of neuronal discharges increases with the increase of twisting angle,and all of them enter the plateau when the twisting angle of acupuncture reaches 180°?240°.(4)In the range of 60°?240°,the dorsal root discharges evoked by different needle twisting angles were positively correlated with the number of discharges,and the dorsal root afferent nerve fiber discharges peaked when the needle twisting angle reached 240°.(5)Temperature stimulation(?40?)can induce the activity of C-HTMR neurons,and the number of C-HTMR neuron discharges increases with the increase of stimulation temperature within the range of 40??52?.(6)"With the increase of stimulation temperature,the discharge frequency of dorsal root afferent fibers increased,and the discharge frequency slowed down with the increase of temperature after the temperature reached 48?Conclusions:(1)Acupuncture can activate the firing of four types of primary sensory neurons:A?,A?,C-HTMR and C-LTMR(2)Although the neuronal firing evoked by acupuncture stimulation was intensity-dependent,the increase became slower after reaching the "plateau".This turning point may be the most appropriate stimulation intensity for acupuncture(3)Moxibustion stimulation can only induce the discharge of C-HTMR neurons,suggesting that moxibustion may play a therapeutic role through the afferent of C-HTMR neurons.Besides,48? may be an appropriate effective stimulation for moxibustion therapy.