The physiological mechanism underlying the acupoint sensitization was evaluated systemically by using the method of electric physiology at spinal cord, medulla, and thalamus levels; the dynamic change of acupoint from the relative "silence" to the relative "activation" function was explained through the study on the dynamic process of acupoint sensitization; the biological process of the therapeutic effect of acupoint stimulation was illuminated through the research of the central mechanism underlining the dose effect relationship between the sensitive acupoint and the related brain area, thus scientific evidence for the functional link between the acupoint and internal organs as well as the nature of the acupoint were provided.
Acupuncture Points ; Acupuncture Therapy ; Animals ; Humans ; Moxibustion ; Nociceptors ; physiology ; Sensation ; Viscera ; innervation ; physiology ; Visceral Afferents ; physiology

Using intracellular potential recording technique in vivo, a series of hyperpolarizing and depolarizing currents at different intensities with a 50-ms duration were injected to somatic nociceptive neurons (SNNs) and somatic non-nociceptive neurons (SNNNs) in the anterior cingulate gyrus (ACG) of cats. The membrane electrical responses of the neurons were recorded, and the membrane electrical parameters of the neurons were calculated for comparative study on membrane electrical properties of SNNs and SNNNs of the ACG. A total of 188 ACG neurons from 57 cats were recorded. Among the 188 neurons, 172 (91.5%) and 16 (8.5%) were SNNs and SNNNs, respectively. The I-V curves of SNNs and SNNNs in the ACG were "S" shapes. When the absolute value of injected current intensity was less than or equal to 1 nA (≤ 1 nA), the I and V of I-V curves of both SNNs and SNNNs were linearly correlated (rSNNs = 0.99, rSNNNs = 0.99). When the absolute value of injected current intensity was more than 1 nA, both SNNs and SNNNs showed a certain inward or outward rectification behavior. Compared with SNNNs, SNNs had stronger rectification and lower adaptability (P < 0.01). With the increase of injected current intensity, the changes of frequency of discharges of SNNs were higher than those of SNNNs. In addition, the membrane resistance (Rm), the membrane capacity (Cm) and the time constant (τ) of SNNs were larger than those of SNNNs (P < 0.05 or P < 0.01). The differences in the membrane electrical properties between SNNs and SNNNs in the ACG suggested the disparity in neuronal cell size and cell membrane structure between them. The results of this study provided the experimental basis for deeply elucidating the mechanisms of somatic nociceptive sensation and characteristics on the membrane electrical aspects of ACG neurons.
Animals ; Cats ; Gyrus Cinguli ; cytology ; Membrane Potentials ; Neurons ; physiology ; Nociceptors ; physiology

No abstract available.
Animals ; Colon/*metabolism ; Constipation/*physiopathology ; Diarrhea/*physiopathology ; Female ; Ganglia, Spinal/*cytology ; Humans ; Irritable Bowel Syndrome/*physiopathology ; Male ; Nociceptors/*physiology ; Receptor, PAR-2/*physiology

OBJECTIVETo investigate the role of heme oxygenase and carbon monoxide (HO/CO) in the development of spontaneous pain and hyperalgesia of rats induced by formalin injection.

METHODSZinc protoporphyrin Znpp (the inhibitor of HO) was intrathecally injected to the rats with formalin inflammatory pain. Hemin (the agonist of HO) was intrathecally injected to the normal rats. The weighted pain scores were used to evaluate the degree of pain response. Thermal withdrawal latency and mechanical withdrawal threshold were observed to assess the degree of thermal hyperalgesia and mechanical allodynia.

RESULTSAfter the intrathecal injection of Znpp, the weighted pain score obviously reduced in a dose-dependent manner compared with the rats with formalin inflammatory pain. Intrathecal injection of Znpp had no obvious effect on thermal withdrawal latency and mechanical withdrawal threshold in injected feet compared with formalin group. But there was a prolongation in a dose-dependent manner in non injected feet. Intrathecal injection of Hemin to normal rats could shorten the thermal withdrawal latency and reduce the mechanical withdrawal threshold on both sides of hindpaws.

CONCLUSIONIntrathecal injection of the HO inhibitor produced prominent inhibition to pain related behavior and thermal and mechanical hyperalgesia induced by formalin injection. Intrathecal injection of HO inductor could induce thermal and mechanical hyperalgesia in normal rats. The results indicated that HO/CO took part in the processes of spinal cord nociceptive information transmission and the development of thermal and mechanical hyperalgesia.

Animals ; Carbon Monoxide ; Formaldehyde ; adverse effects ; Heme Oxygenase (Decyclizing) ; antagonists & inhibitors ; Hemin ; Hyperalgesia ; chemically induced ; Male ; Nociception ; Nociceptors ; drug effects ; physiology ; Pain ; chemically induced ; Protoporphyrins ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo observe the descending modulation of cardiac nociception by the rostral ventromedial medulla (RVM) in rats.

METHODSA rat model of cardiosomatic motor reflex (CMR) was established by injecting capsaicin into the pericardial sac to induce cardiac nociception, and the electromyogram (EMG) response of the dorsal spinotrapezius muscle was studied. The RVM was electrically stimulated (25, 75 and 100 µA) or destroyed to examine whether RVM exerted descending modulation on cardiac nociception.

RESULTSElectrical stimulation of the RVM at 8 sites produced intensity-dependent inhibition of EMG responses to noxious cardiac stimulus (F[2,21]=43.188, P=0.001). Electrical stimulation at 3 sites caused facilitated EMG responses, but the increased magnitude of the EMG was not dependent on stimulation intensity (F[2,6]=0.884, P=0.461). Stimulation at 11 sites produced biphasic effects: at a low intensity (25 µA), the elicited EMG magnitude was significantly larger than baseline (P<0.05), and at greater intensities (75/100 µA), the stimulation caused suppression of the EMG magnitude to a level significantly lower than the baseline (P<0.05). Electrolytic lesion of the RVM resulted in significantly increased EMG responses compared with the baseline and sham lesion group.

CONCLUSIONCardiac nociception evoked by capsaicin stimulation is subjected to descending biphasic modulation by the RVM, which produces predominantly descending inhibition on heart pain.

Animals ; Capsaicin ; pharmacology ; Electric Stimulation ; Electromyography ; drug effects ; Male ; Medulla Oblongata ; physiology ; Nociception ; Nociceptors ; drug effects ; physiology ; Pain ; physiopathology ; Pericardium ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley ; Sensory System Agents ; pharmacology

We developed a method that allows us to label nociceptive neurons innervating tooth-pulp in rat trigeminal ganglion neurons using a retrograde fluorescence-tracing method, to record ATP-activated current in freshly isolated fluorescence-labeled neurons and to conduct single cell immunohistochemical staining for P2X1 and P2X3 subunits in the same neuron. Three types of ATP-activated current in these neurons (F, I and S) were recorded. The cells exhibiting the type F current mainly showed positive staining for P2X3, but negative staining for P2X1. The results provide direct and convincing evidence at the level of single native nociceptive neurons for correlation of the characteristics of ATP-activated currents with their composition of P2X1 and P2X3 subunits and cell size. The results also suggest that the P2X3, but not P2X1, is the main subunit that mediates the fast ATP-activated current in nociceptive neurons.
Action Potentials ; physiology ; Adenosine Triphosphate ; metabolism ; Animals ; Dental Pulp ; innervation ; physiology ; Nociceptors ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, Purinergic P2X1 ; metabolism ; Receptors, Purinergic P2X3 ; metabolism ; Tissue Distribution ; Trigeminal Nerve ; cytology ; metabolism

Despite its clinical importance, the underlying central mechanisms of pruritic behaviors are poorly understood. To investigate the role of nociceptive arcuate nucleus neurons in chloroquine-induced pruritic behaviors in mice, we tested the effect of arcuate nucleus neurons and interscapular brown adipose tissue (IBAT) on itch produced by intradermal injection of chloroquine in the nape of the neck. Our results provide several lines of evidence for an important role of nociceptive arcuate nucleus neurons in chloroquine-induced pruritic behavior: (1) Intradermal microinjection of chloroquine resulted in a dramatic increase in itch behaviors accompanied by the activation of c-Fos positive neurons in arcuate nucleus; (2) Microinjection of chloroquine significantly increased IBAT temperature in the mice. These findings suggested that chloroquine-induced pruritic behaviors were associated with the activity of nociceptive arcuate nucleus neurons.
Animals ; Arcuate Nucleus of Hypothalamus ; drug effects ; physiopathology ; Chloroquine ; adverse effects ; Male ; Mice ; Mice, Inbred C57BL ; Nociceptors ; drug effects ; physiology ; Pruritus ; chemically induced ; physiopathology

OBJECTIVETo observe whether formalin inflammatory pain can induce neuron apoptosis in rats spinal cord or not and the effects of nitric oxide on the spontaneous pain reaction and neuron apoptosis in the spinal cord of rats with formalin inflammatory pain.

METHODSFormalin-induced paw licking time was used to reflect the degree of spontaneous pain of rats, and the flow cytometry was used to detecte neuron apoptosis rate of spinal cord.

RESULTSCompared with control group, the apoptosis ratio of spinal neuron was increased in the rats with formalin inflammatory pain, and peaked at 3d after formalin injection. Pre-intrathecal injection of NOS inhibitor L-NAME inhibited the nociceptive behavioural response in double phases induced by fonnrmalin injection and cut down the neuron apoptosis ratio of spinal cord of rats with formalin inflammatory pain. Nociceptive behavioural response and incraesed neuron apoptosis in the spinal cord were induced by intrathecal injection of L-Arg in normal rats.

CONCLUSIONThe results indicated that formalin inflammatory pain could induce the apoptosis of spinal neurons. The neurons apoptosis was the most significant on the third day after formalin injection. The increased pruduction of NO in spinal cord could promote the transmit of nociceptive information and participate the induction of neuronal apoptosis during the formalin inflammatory pain.

Animals ; Apoptosis ; drug effects ; Formaldehyde ; Male ; NG-Nitroarginine Methyl Ester ; pharmacology ; Neurons ; pathology ; Nitric Oxide ; metabolism ; physiology ; Nitric Oxide Synthase ; antagonists & inhibitors ; Nociceptors ; physiology ; Pain ; chemically induced ; physiopathology ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; pathology ; physiopathology

OBJECTIVETo observe the regional distribution of propofol in canine spinal cord under noxious stimulation.

METHODSTwelve healthy hybrid dogs (12-18 months old, weighing 10-12 kg) were randomly divided into control group (n=6) and stimulation group (n=6). All the dogs were anesthetized with a single bolus dose of propofol (7 mg/kg) in 15 seconds followed by propofol infusion at a constant rate of 70 mg/kg/h via the great saphenous vein of the right posterior limb. In the stimulation group, the tails of the dogs were clamped for 5 min after 45 min of propofol infusion. Blood samples were taken from the internal carotid artery and internal jugular vein at 50 min after propofol infusion to detect plasma propofol concentrations by high-pressure liquid chromatography (HPLC). The dogs were then immediately sacrificed by decapitation and the frontal horn, posterior horn, intermediate zone, frontal funiculus, posterior funiculus and lateral funiculus of the spinal cord were dissected for determination of propol content by HPLC.

RESULTSThe plasma concentrations of propofol in the internal carotid artery and internal jugular vein were 5.07-/+0.23 and 5.03-/+0.10 microg/ml in the stimulation group, respectively showing no significant differences from those in the control group (5.09-/+0.03 and 5.08-/+0.03 microg/ml, P>0.05). In the control group, the propofol concentration was 5.09-/+0.08 microg/g in the frontal horm, 5.10-/+0.08 microg/g in the posterior horn, 5.05-/+0.19 microg/g in the intermediate zone, 5.06-/+0.14 microg/g in the frontal funiculus, 5.06-/+0.15 microg/g in the posterior funiculus and 5.06-/+0.41 microg/g in the lateral funiculus, showing no significant differences (P>0.05). The propofol concentrations in the frontal horn (7.65-/+0.47 microg/g) and posterior funiculus (7.06-/+0.82 microg/g) in the stimulation group were significantly higher than those in the other spinal cord tissues (P<0.05) and those in the control group (P<0.05).

CONCLUSIONAt 50 min after intravenous injection of propofol at a constant rate of 70 mg/kg/h, plasma propofol concentrations in the internal carotid artery and internal jugular vein reaches equilibrium with a balanced distribution in all the spinal cord regions. Propofol concentration can be higher in the frontal horn and posterior funiculus under noxious stimulation.

Animals ; Dogs ; Female ; Male ; Nociceptors ; drug effects ; physiology ; Pain ; physiopathology ; Physical Stimulation ; Propofol ; administration & dosage ; pharmacokinetics ; pharmacology ; Random Allocation ; Spinal Cord ; metabolism

The aim of the present study is to explore the role of anterior cingulate gyrus (ACG) in bilateral cerebral cortex in visceral nociceptive sensation. Electrical stimulation of greater splanchnic nerve (GSN) was used as visceral nociceptive stimulus, and intracellular recording techniques in vivo was used to record and analyze the responses to stimuli and spontaneous electric activities of the neurons in the bilateral ACG. According to the responses to electrical stimulation of GSN, the neurons in the bilateral ACG were divided into GSN-stimulus-relative neurons (GSRNs) and GSN-stimulus-irrelative ones. According to the characteristics of the evoked responses to electrical stimulation of the GSN, GSRNs could be further classified into visceral nociceptive neurons (VNNs) and non-visceral nociceptive neurons (NVNNs). VNNs included specific visceral nociceptive neurons (SVNNs) and non-specific visceral nociceptive neurons (NSVNNs). The results showed that the percentage of GSRNs in the contralateral ACG (38.18%) was significantly higher than that in the ipsilateral ACG (29.49%, P<0.01), suggesting although GSN afferent fibers project to bilateral ACG, they mainly project to the contralateral ACG. Compared with ipsilateral ACG, contralateral ACG possessed lower proportion of SVNNs and higher proportion of NSVNNs (P<0.01). The absolute values of resting potentials (RP) of GSRNs, VNNs, NVNNs and SVNNs in ipsilateral ACG were less than those of corresponding neurons in contralateral ACG. However, there were no significant differences in the absolute values of RP of NSVNNs between ipsilateral and contralateral ACG. There were no significant differences in modes, frequencies and amplitudes of spontaneous electric activities of VNNs and NVNNs between ipsilateral and contralateral ACG. Additionally, the percentage of neurons having spontaneous electric activities from VNNs was significantly higher than that from NVNNs, which indicated that the excitability of VNNs was higher than that of the NVNNs in bilateral ACG. These results suggest that the patterns and degrees of the responses to nociceptive GSN-stimulation of the ipsilateral and contralateral ACG are different, thus providing new experimental data for the asymmetry of functions of the bilateral brain.
Animals ; Cats ; Electric Stimulation ; Evoked Potentials ; physiology ; Female ; Gyrus Cinguli ; physiology ; Male ; Nociceptors ; physiology ; Viscera ; innervation ; Visceral Pain ; physiopathology