Animals ; Cocaine ; pharmacology ; Habenula ; drug effects ; physiology ; Neurons ; drug effects ; physiology ; Pain Threshold ; drug effects ; Rats

STUDY DESIGN: A Multicenter double-blind randomized clinical study comparing Neurotropin and Aceclofenac. OBJECTIVE: To evaluate the analgesic effect, efficacy and safety of Neurotropin in patients with low back pain. SUMMARY OF LITERATURE REVIEW: Non steroidal anti inflammatory analgesics are used as the main medical treatment in patients with low back pain. However, complications, such as gastrointestinal or cardiovascular problems, have been well documented. Neurotropin acts to recover the analgesic state arising from a decrease in pain threshold and has a completely different mechanism to that of existing anti-inflammatory and narcotic analgesics, with its action of restoring the immune system having been confirmed. MATERIALS & METHOD: 376 patients with back pain were randomly divided into two groups; one group was administered Neurotropin and the other Aceclofenac. The overall improvement after 4 weeks was used as the first efficacy variable, and with the second efficacy variable the improvements in spontaneous pain, tenderness, motion pain, radiating pain, severity, pain intensity, and the overall severity and Oswestry Disability Indices were used as the evaluation criteria. To evaluate safety, the abnormal clinical response and alternations on physical examination and the clinical laboratory values were used. RESULTS: A total of 358 patients received the experimental and comparison drugs, of which 351 were evaluated for safety. The overall improvement after 4 weeks, severity of symptoms, overall severity, and the pain intensity and Oswestry Disability Indices were decreased in both groups, but the differences between the two groups were not statistically significant. The overall decrease in the severity was greater in the Aceclofenac group, but both groups had statistically meaningful decreases after the administration of the drugs. i.e. Adverse drug reactions were less in the Neurotropin group, but these showed no significant statistical difference. CONCLUSIONS: Neurotropin and Aceclofenac are equally effective in patients with low back pain, but in terms of safety from a clinical view point Neurotropin is more reliable.
Analgesics ; Back Pain ; Drug-Related Side Effects and Adverse Reactions ; Humans ; Immune System ; Low Back Pain* ; Narcotics ; Pain Threshold ; Physical Examination

The present study was carried out to investigate the effects of neuropeptide Y (NPY) in the midbrain periaqueductal grey (PAG) on the nociceptive modulation in mononeuropathic rats. NPY was microinjected into the PAG. The latency of paw withdrawal (PWL), assessed by the hot-plate (52 ) and the Randall Selitto test, was measured. Intra-PAG administration of 0.05, 0.1 and 0.2 nmol of NPY significantly increased the PWLs in a dose-dependent manner. Co-administration of 0.2 nmol of NPY(28-36) and 5.5 nmol of naloxone significantly attenuated the NPY-induced increase in PWLs. The results suggest that Y(1) receptor may mediate NPY-induced anti-nociception, and that the opioid receptors in PAG may also be involved in this process in mononeuropathic rats.
Analgesics ; pharmacology ; Animals ; Male ; Microinjections ; Mononeuropathies ; physiopathology ; Neuropeptide Y ; pharmacology ; Nociceptors ; drug effects ; Pain ; physiopathology ; Pain Threshold ; drug effects ; Periaqueductal Gray ; physiology ; Rats ; Rats, Sprague-Dawley

AIMTo observe the responses of pain-related neurons in habenula to the nociceptive stimuli and classic analgesic morphine for inquiring into its characteristics of pain.

METHODSThe experiment was proceeded with adult rats under light anesthetized. Through the cannula inserted by operation or the multielectrode injecting the morphine, naloxone, CCK-8 and etc into lateral cerebro-ventricule or habenula, the unit firings from the neurons of habenula were recorded.

RESULTSThe unit firings were recorded from pain-related neurons distributed in MHb or LHb. The pain-related neurons could be differentiated into pain excitatory or pain inhibitory neurons. After the morphine iontophoresed, the main response of the pain excitatory neurons was inhibited, the pain inhibitory neurons were excited. The naloxone iontophoresed could antagonize the analgesic effect of morphine on neurons of habenula. After the morphine injected (10 mg/kg, i. p) into morphine-tolerated rats, the analgesic efficacy of pain-related neurons in LHb was more stronger than in MHb. It showed that the neurons in LHb were suffered from morphine was higher than MHb. After injection of antagonist of CCK-8 into lateral cerebro-ventricle, morphine injected peritoneally could weaken the tolerance level of morphine. Conversely, after injection of morphine (10 mg/kg, i. p.) 10 min, second time injection of CCK-8 (15 ng/10 microl) into lateral cerebro-ventricle could antagonize the analgesic action of morphine on the neurons in LHb, but in MHb the antagonized action was not obviously.

CONCLUSIONThe excitatory and inhibitory neurons in Hb were sensitive to the nociceptive stimuli and not easy to adapt to it. The sensitivity of the neurons in LHb to morphine was more higher than the neurons in MHb.

Animals ; Habenula ; cytology ; drug effects ; Morphine ; pharmacology ; Naloxone ; pharmacology ; Neurons ; drug effects ; physiology ; Pain Threshold ; drug effects ; Rats ; Rats, Wistar ; Sincalide ; pharmacology

OBJECTIVETo investigate the effect of L-838,417 on the results of behavioral test in rats with experimentally induced trigeminal neuralgia.

METHODSMale SD rats were randomized into model group (n=34), sham-operated group (n=30) and control group (n=6). Thirty rats with trigeminal neuralgia induced by chronic constriction injury of the infraorbital nerve below the zygomatic bone were randomly divided into 5 equal groups for treatment with 1.0 mg/kg L-838,417 (L1 group), 10.0 mg/kg L-838,417 (L10 group), 5 mg/kg morphine (M group), 3 mg/kg diazepam (D group), or normal saline (NS group). The pain threshold of the tentacles pad to von-Frey filament stimulation was measured in the rats before and at 1, 2, 3, 4, 5 h after the treatments. The sedative effect of L-838,417 was evaluated by recording the position scores and righting reflex scores, and the drug tolerance was also evaluated.

RESULTSNine days after the operation, the pain threshold of the rats in the model group was significantly decreased compared with that before operation and that of the sham group (P<0.01). The threshold of L1 and L10 groups were both significantly increased 1 h after L-838,417 administration (P<0.01). The rats in the NS, L1, and L10 groups did not show unusual posture or righting reflex. In L1 and L10 groups, L838,417 did not show attenuated efficacy after prolonged use (10 days).

CONCLUSIONL-838,417 can effectively improve hyperalgesia in rats with trigeminal neuralgia without causing sedation, motor impairment, or drug tolerance.

Animals ; Fluorobenzenes ; pharmacology ; Hyperalgesia ; drug therapy ; Male ; Pain Measurement ; Pain Threshold ; drug effects ; Rats ; Rats, Sprague-Dawley ; Triazoles ; pharmacology ; Trigeminal Neuralgia ; drug therapy ; physiopathology

AIMTo determine the involvement of NO signal pathway in the development of hyperalgesia induced by activation of protein kinase C (PKC ), nociceptive responses and nitric oxide synthase(NOS) expression and nitric oxide (NO) content in the spinal cord were observed after administration of Phorbol 12-Myristate-Acetate (PMA), a PKC agonist, in rats.

METHODSNociceptive response was observed by behavioral approach. Pain threshold was assayed using thermal tail-flick test. NADPH-d histochemistry was used to investigate the changes of NOS expression. Nitrate/nitrite (NO3-/NO2-) was assayed to represent NO content of lumbar enlargement of spinal cord.

RESULTSNociceptive response was induced and pain threshold decreased after intrathecal injection of PMA. The number of NADPH-d positive cells increased significantly in the superficial layer of the spinal cord dorsal horn (Laminae I - II ) and the grey matter surrounding the central canal (Laminae X), and the reactive degree of NADPH-d positive soma and processes and NO content of the lumbar enlargement of the spinal cord increased significantly after intrathecal injection of PMA. Pretreatment of PKC inhibitor chelerythrine chloride blocked the changes induced by PMA.

CONCLUSIONThe activation of PKC in the spinal cord neurons might induce spontaneous nociceptive responses and hyperalgesia in rats, as well as promote NOS expression and NO production, suggesting that increase in NO production is one of mechanisms of hyperalgesia induced by activation of PKC.

Animals ; Enzyme Activators ; pharmacology ; Nitric Oxide ; biosynthesis ; Nociception ; drug effects ; Pain Threshold ; drug effects ; Protein Kinase C ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; drug effects ; Spinal Cord ; drug effects ; metabolism ; Tetradecanoylphorbol Acetate ; analogs & derivatives ; pharmacology

OBJECTIVETo evaluate the effects of tramadol on the proinflammatory responses in a rat model of incisional pain by investigating its effects on nociceptive thresholds and serum interleukin-6 (IL-6) and IL-2 levels.

METHODSForty-two male Sprague-Dawley (SD) rats scheduled for plantar incision were randomly divided into 7 groups (n=6 in each group). Rats in Group 1 receiving general anesthesia with no incision were served as control; At 30 min before skin incision, Groups 2 to approximately 5 were given 5 ml normal saline or 1, 10, and 20 mg/kg tramadol, respectively, intraperitoneally (i.p.); Group 6 received 10 mg/kg tramadol after operation; Group 7 received 10 mg/kg tramadol before incision, followed by 200 microg/kg naloxone after operation. Mechanical allodynia was measured by electronic von Frey filament to evaluate the nociceptive thresholds 1 h before incision, and 1 h and 2 h after operation. Serum IL-6 and IL-2 levels were measured by enzyme-linked immunosorbent assay (ELISA) 2 h after operation.

RESULTSMechanical thresholds decreased significantly and serum IL-6 level increased significantly after operation in Group 2 compared with control (P<0.01), and these changes were reversed respectively by tramadol in a dose-dependent manner (P<0.05 and P<0.01, respectively). IL-2 level remained unchanged after operation in Group 2, but decreased in Group 3 (P<0.05), then gradually returned to the normal level in Groups 4 and 5. The intraperitoneally injected tramadol (10 and 20 mg/kg) produced a potent and dose-dependent antinocicptive effect on the lesioned paw. The antinocicptive effects of tramadol were partially antagonized by naloxone (200 microg/kg), suggesting an additional non-opioid mechanism.

CONCLUSIONThe results suggest that tramadol could be a good choice for the treatment of pain under the conditions that immunosuppression may be particularly contraindicated.

Analgesics, Opioid ; pharmacology ; Animals ; Dose-Response Relationship, Drug ; Interleukin-2 ; biosynthesis ; blood ; Interleukin-6 ; biosynthesis ; blood ; Male ; Pain Measurement ; methods ; Pain Threshold ; drug effects ; Pain, Postoperative ; blood ; drug therapy ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Tramadol ; pharmacology

OBJECTIVETo investigate the influence of dopamine (DA) and DA receptor's antagonist on the transmission of noxious information in the central nervous system of normal rats or morphinistic rats.

METHODSThe influence of DA on the electric activity of the pain-excited neuron (PEN) in the caudate nucleus (Cd) of normal rats or morphinistic rats was recorded after the sciatic nerve was noxiously stimulated.

RESULTSDA shortened the average latency of the evoked discharge of PEN in the Cd of normal rats, indicating that DA could increase the activity of PEN and pain sensitivity in normal rats. This effect could be inhibited by Droperidol. DA increased the average latency of the evoked discharge of PEN in the Cd of morphinistic rats, indicating that DA could inhibit the activity of PEN and pain sensitivity in morphinistic rats.

CONCLUSIONThe responses to painful stimulation were completely opposite between normal rats and morphinistic rats after the intracerebroventricular injection of DA.

Action Potentials ; drug effects ; physiology ; radiation effects ; Analysis of Variance ; Animals ; Caudate Nucleus ; drug effects ; Disease Models, Animal ; Dopamine ; pharmacology ; Dopamine Antagonists ; pharmacology ; Droperidol ; pharmacology ; Drug Interactions ; Electric Stimulation ; adverse effects ; Female ; Male ; Morphine Dependence ; physiopathology ; therapy ; Neurons ; drug effects ; Pain ; drug therapy ; etiology ; physiopathology ; Pain Threshold ; drug effects ; Rats ; Rats, Wistar ; Reaction Time ; drug effects ; physiology ; radiation effects

AIMTo study the cutaneous permeation kinetics and pharmacodynamics of lidocaine gel.

METHODSThe concentration of lidocaine in dermis following topical application in rats was determined by the cutaneous microdialysis technique and related parameters were calculated; the pharmacodynamics of the gel was evaluated by electric stimulation method with EMLA (eutectic mixture of local anesthetics) cream as a control.

RESULTSThe peak of percutaneous absorption kinetic profile of lidocaine gel across rat skin occurred at 1.25 h; the onset time of local anesthetic action of lidociane gel was similar to that of EMLA, but both the duration and depth of anesthetic effect were superior to EMLA cream.

CONCLUSIONLidocaine gel showed good anesthetic effect. The minimum effective concentration of lidocaine in dermis is 12 mg.L-1.

Anesthesia, Local ; Anesthetics, Local ; pharmacokinetics ; pharmacology ; Animals ; Gels ; Lidocaine ; pharmacokinetics ; pharmacology ; Male ; Pain Threshold ; drug effects ; Prilocaine ; pharmacokinetics ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar ; Skin Absorption

AIMTo compare the antagonistic effects of 6 beta-naltrexol and naltrexone against morphine analgesia.

METHODSThe effects of 6 beta-naltrexol and naltrexone against morphine analgesia were observed in mouse heat radiant tail-flick assay and in mouse (55 +/- 1) degrees C hot plate test. The displacement of 6 beta-naltrexol and naltrexone on binding to CHO-mu receptor was observed by radioligand binding study.

RESULTS6 beta-naltrexol antagonized morphine analgesia but the potency was (6.1 +/- 1.7)% that of naltrexone. The effective duration of 6 beta-naltrexol was 3-4 times that of naltrexone and the peak time of the response was about 0.5-1 h after s.c. equivalent efficacy dose (ED95) in two models. Like naltrexone, 6 beta-naltrexol was effective by oral administration and the potency ratio of p.o./s.c. was 1/3. As an antagonist to opioid receptor, the displacement of 6 beta-naltrexol was about 12.5% that of naltrexone, which was almost in agreement with the efficacies against morphine analgesia in mouse.

CONCLUSIONCompared with naltrexone, 6 beta-naltrexol was less potent but duration was longer.

Analgesia ; Analgesics, Opioid ; antagonists & inhibitors ; Animals ; Female ; Male ; Mice ; Morphine ; antagonists & inhibitors ; Naltrexone ; analogs & derivatives ; pharmacology ; Narcotic Antagonists ; pharmacology ; Pain Threshold ; drug effects ; Receptors, Opioid, mu ; metabolism