The Role of GABAA Receptor Inhibitor on Morphine Antinociception Action in...

[Full title: The Role of GABAA Receptor Inhibitor on Morphine Antinociception Action in Cuneiformis Nucleus]

[Find the meaning and references behind the names: Life, Data]

Life International Journal of Pharmacology ISSN 1811-7775 Life science alert ansinet Asian Network for Scientific Information

[Find the meaning and references behind the names: Mpe, Amino, Clark, Magnus, Human, Deg, Cutting, Left, Gilbert, Key, Male, Tax, Ils, Dose, Brain, Plus, Fields, Drew, Pain, Behbehani, Gray, Pomeroy, Kerman, Central, Flick, Abbas, Main, Horn, Live, Areas, Iran, Micro, Iii, Franklin, Dlf, Mozaffar, Pag, Supra, Hamid, Mri, Pac, Acid, Gaba, Arcas, Post, Levy, Fixed, Play, Pan, Millan, Due, Ato, Role, Ach, Light, Author, Study, Bernard, Min, Tel, Cord, Kaplan, Tail]

International Journal of Pharmacology 2 (1): 100-105, 2006 ISSN 1811-7775 2006 Asian Network for Scientific Information The Role of GABA Receptor Inhibitor on Morphine Antinociception Action in Cunciformis Nucleus 'Mozaffar Rezvanipour, Abbas Haghparast and Hamid Millan Department of Physiology, Medical School. Kerman, Iran "Kerman Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran Abstract: In order to investigate the role of cuneiformis (CnF) in pain modulation, we evaluated the effect of GABA, antagonist. (bicuculline) on antinociceptive response of morphine in this nucleus. Eighty live male N-MRI rals. weighing 250-350 g were used, they were maintained on a 12 h light/clark cycle al 22-24°C. The animals were anesthetized with pentobarbital sodium (60 mg kg¯¹ ip) and were fixed on a stereolaxie apparatus. Then CnF was calculated and the animal was left to recovery for one week. The animals were divided into 4 groups; group I which received 0.5 μL of different doses of bicuculline dissolved in saline (12.5, 25, 50 and 100 ng), group II which received morphine (10g/0.5 μL saline), group III which received a dose of bicuculline (50 ng/0.5 μL saline) plus morphine (10g/0.5 μL saline) that followed with receive of naloxone (2 mg kg¯, i.p.) and group IV; which received 0.5 μL saline and served as control. Tail Flick Latency (TFL) was measured as an index of pain during 2, 7, 12, 17, 22 and 27 min post micro-injection in CnF in all groups. Micro-injection of bicuculline in CnF increased TTL dose dependently. Morphine + bicuculline significantly increased maximum possible effect (%MPE) of antinociceptive response compared with morphine or bicuculline alone. Naloxone decreased the response to morphine. The results of this study indicates that CnF has a significant role in pain modulation, gabaergic system and opioid analogs have also play an important role on its antinociception. Key words: GABA, morphine, cuneiformis, antinociception INTRODUCTION Descending inhibitory system from Rostral Ventromedial Medulla (RVM), Nucleus Raphe Magnus (NRM), Nucleus Magnucellularis (NMC) and Pericquictal Gray (PAG) have regulatory action on spinal cord (Pomeroy and Behbahani, 1979). The main source of projections to RVM and NMC ato PAG and ils lateral nucleus cunciformis (CF) (Bernard et al., 1989), there be electrical excitation of CnF will increase tail flick latency (TFL) via acting on NRM and NMC (Behbehari and Zemlan, 1986; Bernard et al.. 1989). Gamma amino butyric acid (GABA) is the main inhibitory neurotransmitter, in central nervous system (CNS), which is found in most areas of the human brain. It can interact with three found type of GABA receptor, namely GABA GABA and GABA, (Drew et al., 1984). Cnf that is located in ventro lateral region of PAG is an inhibitory descending system, as PAC and RVM it has opioid receptors and is sensitive to their antinociceptive effects (Pan and Fields, 1996; Zemlan and Behbehani, 1988). Increasing of GABAergic inputs to off-cells of RVM. facilitate pain reflex and micro-injection of CGP (GABA antagonist) to RVM activate off-cells and so antinociception effects overcome (Drew et al., 1984; Heinricher and Kaplan, 1991). Increasing of action of off-cells due to morphine injection to RVM, are through of a disinhibition of a GABAergic interneuron (Heinricher et al., 1992). Backofen as a GABA agonist, causes antinociception via effecting on spinal and supra spinal arcas (Cutting and Forban. 1975; Levy and Proudfit, 1997; Sabetkasai et al., 1999). Micro-injection of morphine in to PAG causes antinociception with activation of RVM. Teurons (Behbehani and Pomeroy, 1978; Pomeroy and Behbahari, 1979). However, RVM is source of axons that come from brain stem through dorsolateral fumiculus (DLF) to dorsal horn of spinal cord which is the destinations for primary pain afferents (Ileinricher et al., 1992). Neurons in CnF have excitatory receptors to glutarate (Sabetkasai et al., 1999) and acetycholine (Ach) (Behbehani and Zemlan, 1986) and inhibitory receptors to GABA (Gilbert and Franklin, 2001; Nemmani and Mogil, 2003). Electrical excitation of Corresponding Author: Dr. Mozaffar Rezvanpour, Department of Physiology, Medical School, Kerman, Iran Tel: 198-311-2110482 Tax: 198-311-3221671 400

[Find the meaning and references behind the names: Every, Steel, Aller, Heal, Hole, Supa, Intl, Dental, Urban, Stainless, Present, Allas, Frame, Prior, Cage, Time, Keep, Cut, Six, Part, Watson, Smith, Point, Tip, Rat, Sec, Guide, Area, Mean, Dark, Rate, Free, Mahmoudi, Hamilton, Piece, Lamp, Sham, Dura, Beam, Mrt, End, Tran, Skull]

Intl. J. Pharmacol., 2 (4): 400-405, 2006 CuF activate pain modulating descending system (Bernard et al., 1989). Regarding effect of la cerebroventricular injection of GABA receptor agents on morphine-induced antinociception (Mahmoudi and Zarrindast, 2002) and also CnF projections to RVM. central nucleus of amygdale. PAG and other forebrain regions (Bernard et al., 1989; Gilbert and Franklin, 2002), we can conclude that pain defending system begins from CnF may be GABAergic and reaction between opioids and GABA receptors occur in this nucleus. Our earlier studies with micro-injection of GABA, (Rezvanpour et al., 2004) and GABA, (Rezvanipour et al.. 2005) agents into CF nucleus by formalin test showed that GABA and GABA receptors in CnF have antinociception effects in chronic pain and GABAergic system via opioid receptor induced antinociception in the formalin test.. In the present study, the antinociceprive effects of GABA receptor antagonist in the presence or absence of morphine was investigated in rat by thail flick test with micro-injection of bicuculline in CuF. MATERIALS AND METHODS Animals: Ninely six male N-MRT rals (weighing 200-250 g) were used in these experiments. Animals were kept 3 per cage (15 x 30 x 15 cm) at an environmental temperature of 22+3°C and a 12 h light-dark cycle. The animals had free access to food and water except during the time of experiments. Each animal was used once only and was euthanized immediately after the experiment. Surgical procedure: Animals were anesthetized with sodium thiopental (45-60 mg kg ') intraperitoneally (i.p.) and placed in a stereotaxic frame. A sagittal incision was made from anterior to posterior area of skull. The position of cunciformis nucleus was estimated according to Paxinos and Watson allas (Paxinos and Watson et al., 1987). A hole (2 mm in diameter) drilled in the skull above the CnF and the dura reflected to allow the placement of guide cannula into the region. A guide cannula (5.3 mm in length) was inserted stereotaxically into the area of CuF (AP 8.3 mm, L = 1.7 mm and D 6.3 mm with references to Bregma and the cortical surface, respectively) and secured to skull with dental cement. A stainless steel dummy camula was inserted into guide carmula and remained there when the guide cannula was not in use. The animals were allowed to recover from surgery for at least one weak prior to the initiation of experimental protocol, to accommodate for handling stress (Heinicher et al., 1987). Micro-injection of bicuculline and morphine were made through a 33 gauge injection cammula that extended 3 mm below the 25 gauge guide cannula tip. All micro infusions were administered in a volume of 0.5 μL saline at a rate of 0.1 μL every 10 sec. through a stainless steel internal cannula (30) gauge, Supa Co, Tran). This cannula was connected to a 1 ul. Hamilton syring by a 23 cm piece of polyethylene tubing (PE-20) filled with drug solution. Morphine sulfate (Temad Co, Iran) was dissolved in nomal saline and then micro injected slowly into the CnF. A stylet was inserted into the cannula to keep it patent prior to injection. The injection needle was retained in the guide cannula for an additional 60 sec after injection to facilitate the diffusion of the drug. Analgesic test: Tail-flick apparatus was used to evaluate the antinociceptive activity in eight groups of rats. The intensity of the radiant lamp was adjusted to provide baseline levels of 3.0 to 3.5 sec. The same setting was used for all groups (Heinricher and Kaplan, 1991). Each part of the tail in control and treated groups tested only once after saline or drug treatment to avoid unnecessary pain associated with radiant heal. The end. point was tail-flick response sufficient to interrupt the photoelectric beam or a cut-off point of 10 sec. Data were expressed as tail-flick latency (TFL), or as percentage of maximum possible effect (%6MPE), which was calculated as (Urban and Smith, 1994): %MPCPost-drug latency (sec) - Baseline latency (sec) Cut-off value(10sec)-Baseline latency (sec) The tail-flick latency time in intact (without any manipulation) and sham-operated (after surgical operations and recovery without any drug micro-injection into the CnF) rals, was measured for 20 min al 5-min intervals (0, 5, 10, 15 and 20 min; 5 trials). Following determination of baseline TFL (mean of 5 TFL. trials), 0.5 μT, saline or morphine (10 µg/0.5 µl saline) was infused into the Cnl' over a period of approximately 1 min. Two min later, TFL was measured at 5 min intervals for the period from 2 to 27 min (6 trials) post micro-injection. In main experiments, 0.5 μL from different doses of bicuculline were micro injected into the CF and 2 min later TFL was measured at 5 min intervals for the period from 2 to 27 min (6 trials) and finally in bicuculline + morphine group. one in aller micro-injection of bicuculline (50 ng), 10g morphine was injected into the CnF and TFL was measured in 6 trials as in previous group. In the bicuculline morphine group after measuring TFL, animals received naloxone (2 mg kg, ip) to reverse the effect of morphine and TFL was measured again in 5 and 10 min post injection. 401

[Find the meaning and references behind the names: Bic, Less, Sky, Fig, Standard, Til, Bio, Hand, Dye, Days, Hoc, Last, Dala, Rak, Blue, Sem, Atlas, Shown]

Intl. J. Pharmacol., 2 (4): 400-405, 2006 Animals groups: Control groups: Telling intact. ( 15), sham-operated (cannulated) (n-11) and saline treated (n -11). Morphine group: (n = 10). Bicuculline groups: 12.5 g ( 7), 25 ng (n. 10), 50 ng (n-10) or 100 ng (n = 12) of bicuculline in 0.5 µT, saline was injected into the CnF. Bicuculline: (50 ng) +morphine (10 µg) (n = 10). Statistical analysis: Dala are expressed as mean SEM (standard error of mean). TFL time and %MPE in treated groups before and after drug administration were compared by Student's paired t-test and repeated measures analysis of variance (ANOVA) followed by protected Tukeys test for multiple comparison. On the other hand, data in all groups were subjected to the Oneway and/or two-way ANOVA followed by Post-hoc analysis, as needed p-values less than 0.05 were considered to be statistically significant. Histological verification: At the completion of the experiment, protamine sky blue dye micro-injection (0.5 μL) into the CnF was done through the guide cannula. Then the rats were sacrificed with a lethal dose of sodium thiopental (100 mg kg¯', i.p.). Brain was removed and fixed with 10% formalin solution for no less than three days and then the brain coronal slices (50-100 µm) were prepared and examined by light microscopy for the site of injection into the Cnl according to the atlas of Paxinos and Watson (Paxinos and Walson, 1987). All data have been reported here are only from animals which cannula placements were confirmed for the Cnl''. RESULTS Figure 1 shows that TFL, limes were no significantly different in intact, sham-operated (canulated) and salinetreated groups, so the saline-treated group, which received 0.5 uL saline by micro-injection into the Cnl, was regarded as control group. The TTL time was 4.11±0.16 sec in this group. Figure 2 indicates that bicuculline dose dependently increased maximum analgesic response (MPE) in comparison with saline and this response decreased in last minutes. The results of comparison TTL induced by morphine (10 ug), bicuculline (50 ng), bicuculline + morphine are (rak) kopati 11 | | | Control Sham-operated Saline Fig. 1: Tail flick latency (TFL) time in control. sham-operated and saline micro injected groups (n=11-15). No significant difference was seen between these groups. (p<0.05 was considered significant statistically) MPE (%) 1007 90BO- 70- 60- 50- 40- 30- 20- 10- 0- -10- 7 12 17 Time after injection (min) -O-Saline ✓ Bio (12.5) -Bic (25) --Bic (50) --Bic (100) Fig. 2 MPE percentage due to injection of different doses of bicuculline compared to saline injection (n = 7-12) *** p<0.001, ** p<0.01, *p<0.05 shown in Fig. 3. The results indicates that analgesic response was started 2 min after micro-injection of morphine and bicuculline, but TIL was maximum in 27 and 2 min after injection in morphine and bicuculline treated groups, respectively. No difference was found between control and saline treated groups in all of times. TFT, in bicuculline +morphine is significantly more than morphine in 2,7 and 12 min after injection. The injection of naloxone (ip) eliminated only the effect of morphine. 402

[Find the meaning and references behind the names: Siddall, Nal, Agreement, Spinella, Richter, Major, Olmos, Edwards, Tortorici, Plays, Mor, Cheng]

TF latency (sec) 10- 9 5 H 4 3 Control 2 7 12 17 Intl. J. Pharmacol., 2 (4): 400-405, 2006 ---Saline → Morphine Bicuculline + Bic-Mor 22 27 Nal Time after injection (min) Fig. 3: Comparison of Tail flick latency (TTL) time after micro-injection of Saline (0.5 µL). morphine (10 µg/0.5 μL saline). bicuculline (50 ng/0.5 μL saline) and bicuculline morphine (50 ng + 10 μg/0.5 μT. saline) in CnF following injection of naloxone (2 mg kg ip) (n = 10-15) *p<0.05, **p<0.01, ***p<0.001 compared to saline. p<0.01 between bicuculline morphine and morphine DISCUSSION The Cnf is considered as a part of the analgesia system which modulate the pain through its anatomical connections with other part of the pain modulating system, especially with periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) which are the major targets for supraspinal analgesic actions of opioids (Edwards and de Olmos, 1976; Zemlan and Behbehani 1984, 1988). Although the anatomical connections of CnF with other pain modulating systems has been studied (Bemand et al., 1989; Zemlan and Behbehani, 1984), but. the neurophysiology of CnF has not been studied completely. The opioid receptors are found in the pain modulating system in CNS, especially PAG and RVM (Heinricher et al. 1987, 1992; Heinricher and Tortorici. 1991). Other studies showed the presence of enkephalins on the Cnf that could modulate pain (Siddall et al., 1994; Spinella et al., 1996). Others showed that there was a significant increase in TFL time 5 min after electrical stimulation of CnF and pretreatment with naloxone inhibited analgesic response of CnF to electrical stimulation (Behbehani and Zemlan, 1986; Zemlan and Behbehari, 1988). In the present study, micro-injection of morphine into the CF increased TFL time and analgesic response in rats, which was reversed by naloxone. These results indicate that Cnf has opioid receptors, which are involved in pain modulation and the probably analgesic effect of morphine is through its binding with opioid receptors. These results are in agreement with the results of previous studies in other part of the CNS pain modulating system including PAG (Cheng et al., 1986) and os previous studies CuF Tiucleus (Rezvanipour et al., 2004, 2005). wzr The other studies indicated that Cn through its connection with PAG could modulate pain indirectly via a powerful effect on NRM and nucleus reticularis gigantocellularis (NRGC) in RVM (Bernard et al., 1989; Reichling and Basbaum, 1990; Zemlan and Behbehani 1988). About 75% of neurons in NRM respond to the electrical stimulation of CnF through DLF to inhibit nociceptive responses in the dorsal horn of spinal cord (Behbehani and Zemlan, 1986, Richter and Behbehani et al., 1991), which indicate that CF plays a role in pain modulation via RVM. The analgesic response to electrical stimulation or opioid administration into the PAG mediates by on-cells and off-cells (Heinricher et al., 1987; Pan et al., 1990). Off-cells are inactivated by noxious stimuli, but analgesia causes the activation of off-cells that modulate pain control (Heinricher and Kaplan, 1991; Heinricher et al., 1992). Since the PAG and CF have ultrastructural similarities it seems that CnF has also on and off-cells which modulate the analgesic effects of opioids, however further investigation is needed to prove this hypothesis. It suggests that CF has inhibitory GABAergic output neurons (off-cells), which are corrected to PAG and RVM nucleus and inhibition of off-cells in CnF by lidocaine micro-injection causes an increase in TFL time (Pan et al., 1990 Reichling and Basbaum, 1990). It seems bicuculline as a GABAA antagonist causes disinhibition of GABAergic inhibitory RVM off-cells neurons that originate from CnF. In this study, micro-injection of morphine plus bicuculline in CF caused maximum analgesic response but this effect was not reversed completely by naloxone. This results indicate that morphine and GABAA antagonist (bicuculline) induce independent analgesic effects. This finding is not completely in agreement with our studies with GABA, agents (Rezvanipour et al., 2005, 2004) In conclusion, the results of this study showed that cunciformis nucleus has ']. significant role 111 antinociception and GABAergic system and opioid analogues have important shares on this antinociception. 403

[Find the meaning and references behind the names: Williams, Guinea, Press, Ral, San, Evidence, Besson, Pig, Single, Safari, October, Osborne, Morgan, Berard, Ther, Lett, Johnston, Comp, Sincere, Diego]

Intl. J. Pharmacol., 2 (4): 400-405, 2006 ACKNOWLEDGMENTS Our sincere thanks to Kerman Neuroscience Research Center for their help and financial support during this study. REFERENCES Behbehani, M. M. and F.P. Zemlan, 1986. Response of nucleus raphe magnus neurons to electrical Role of stimulation of nucleus cuneiformis: acetylcholine. Brain Res., 369: 110-118. Behbehani, M.M. and S.L. Pomeroy, 1978. Effect of morphine injected in periaqueductal gray on activity of single units in nucleus raphe magnus of the rat. Brain Res., 149: 266-269. Berard, J.F. and M. Peschanski and J.M. Besson, 1989. Afferents and efferents of the rat cuneiformis nucleus: An anatomical study with reference to pain transmission. Brain Res., 190: 181-185. Cheng, Z.F. and II.L. Fields and M.M. IIeinricher, 1986. Morphine micro injected into the periaqueductal gray has differential effects in 3 classes of medullary neurons. Brain Res., 375: 57-65. Culling: D.A. and C.C. Forban, 1975. Alternative approaches to analgesia, baclofen as a model compound. Br. Pharmacal., 54:171-182. Drew, CA. and G.A.R. Johnston and R.P. Weatherby, 1984. Bicuculline insensitive GABA receptors; studies on the binding of (-) baclofen to ral cerebellar membranes. Neurosci. Lett., 52: 317-321. Edwards, S.B. and J.S. de Olmos, 1976. Autoradiographic studies of the projections of the midbrain relicular formation: Ascending projections of nucleus cunciformis. J. Comp. Neurol., 165: 417-431. Gilbert, A.K. and K.B. Franklin, 2001. GABAergic modulation of descending inhibitory system from the rostral ventromedial medulla (RVM). Dose response analysis of nociception and neurological deficits. Neurosci. Lett., 52: 317-321. Gilbert A.K. and K.B. Franklin, 2002. The role of descending fibers from the rostral ventromedial medulla in opioid analgesia in rats. Eur. J. Pharmacal.. 119: 75-81. Heinricher, M.M. and Z.F. Cheng and H.L. Fields, 1987. Evidence for two classes of nociceptive modulating neurons in the periaqueductal gray. J. Neurosci., 7: 271-278. Heinicher, M.M and H.J. Kaplan, 1991. GABA-mediated inhibition in rostral ventromedial medulla: Role in nociceptive modulation in the lightly anesthetized ral. Pain, 17: 105-113. Heinricher, M.M. and M.M. Morgan and H.L. Fields, 1992. Direct and indirect actions of morphine on medullary neurons that modulate nociception. Neuroscience, 48: 533-543. Heinricher, M.M. and V. Tortorici, 1991. Interference with GABA transmission in the rostral ventromedial medulla: Disinhibition of off-cells as a central mechanism in nociceptive modulation. Neuroscience. 63: 533-546. Levy, R.A. and II.K. Proudfit, 1997. The analgesic action of baclofen. J. Pharmacal. Exp. Ther., 2000; 437-442. Mahmoudi, M. and M.R. Zarrindast, 2002. Effect of intracerebroventricular injection of GABA receptor agents on morphine-induced antinociception in the formalin test. J. Pharmacal., 10: 85-91 Nemmani, K.V. and S.L. Mogil, 2003. Serotonin-GABA interactions in the modulation of mu- and kappaopioid analgesia. Neuropharmacology, 44: 304-310. Pan, Z.Z. and H.L. Fields, 1996. Endogenous opioidmediated inhibition of putative pain modulating neurons in rat rostral ventromedial medulla. Neuroscience, 74: 855-862. Pan, Z.Z. and J.T. Williams and P.B. Osborne, 1990. Opioid actions on single nucleus raphe magnus neurons from rat and guinea pig in vitro. J. Physiol., 427: 519-532. Paxinos, G. and C. Watson, 1987. The Rat Brain in Stereotaxic Coordinates. 2nd Edn., San Diego, California, Academic Press Inc., pp: 51. Pomeroy, S.L. and M.M. Behbahani, 1979. Physiologic evidence for a projection from periaqueductal gray to mucleus raphe magnus in the rat. Brain Res., 176: 143-147. Reichling, D.B. and A.1. Basbauni, 1990. Contribution of brainstem GABAergic circuitry to descending antinociceptive controls: II. Electron microscopic immunocytochemical evidence of GABAergic control over the projection from the periaqueductal gray to the nucleus raphe magnus in the rat. J. Comp. Neurol. 302: 378-393. Rezvanipour, M., M. Bakhshesh V. Sheibani. R. Farazifard, 2005. The effect of micro-injection of GABA receptor agents on antinociceptive effect of morphine by formalin test in rat. 17th Iranian Congress of Physiology and Pharmacology, KermanIran 1-4 October 2005,174, Abstract. Rezvanipour, M., T. Safari and M. Abasnejad, 2004. A surly of the effect of intracimciformis nucleus microinjection of GABA receptor agonist and antagonist on antinociceptive effect of morphime by formalin test in ral. J. Kenman University of Medical Sciences, 11: 212-218. 404

[Find the meaning and references behind the names: Polson, Copper]

Intl. J. Pharmacol., 2 (4): 400-405, 2006 Richter, R.C. and M.M. Behbahani, 1991. Evidence for glutamic acid as a possible neurotransmitter between the mesencephalic nucleus cuneiformis and the medullary nucleus raphe magnus in the lightly anesthetized rat. Brain Res., 511: 279-289. Sabetkasai, N., S. Khansefid, H. Yahyavi and M.R. Zarrindast, 1999. Baclofen and antidepressant-induced antinociception in formalin Test: Possible GABA mechanism involvement. Psychopharmacology, 112: 126-131. Siddall, P.J. and J.W. Polson and R.A. Dampney, 1994. Descending antinociceptive pathway from the rostral ventrolateral medulla: A correlative anatomical and physiological study. Brain Res.. 645: 61-68. Spinella, M. and M.L.. Copper and R.J. Boxnar. 1996. Excitatory amino acid antagonists in the rostral ventromedial medulla inhibit masencephalic morphine analgesia in rats. Pain, 64: 545-552. Urban, M.O. and D.J. Smith, 1991. Nuclei within the rostral ventromedial medulla medialing morphine antinociception from the periaqueductal gray. Brain Res., 652: 9-16. Zelan F.P. and M.M. Behbehari, 1984. Afferent. projections to the nucleus Cuneiformis in the rat. Neurosci. Lett., 52: 103-109. Zemlan F.P. and M.M. Behbehani. 1988. Nucleus cuneiformis and pain modulation: Anatomy and behavioral pharmacology. Brain Res.. 453: 89-102. 405

Other Health Sciences Concepts:

[back to top]

Discover the significance of concepts within the article: ‘The Role of GABAA Receptor Inhibitor on Morphine Antinociception Action in...’. Further sources in the context of Health Sciences might help you critically compare this page with similair documents:

Pain, Spinal Cord, Chronic pain, Neuroscience, Statistical analysis, P Value, One-way ANOVA, Repeated measures analysis of variance, Tail flick response, Gamma-amino butyric acid, Naloxone, Student's paired t-test, Brain Stem, Light microscopy, Sham operated, Cut-off point, Two-way ANOVA, Baclofen, Maximum analgesic response, Neuropharmacology, GABAergic system, Psychopharmacology, Acetycholine, Formalin test, Antinociceptive effect, Morphine, Dose-dependently, GABA receptor, Opioid receptor, Morphine sulfate, Post-hoc Analysis, Disinhibition, Bicuculline, Tail flick latency, Eur J Pharmacol, Neuroscience Letters, Glutamate, Dorsal horn, J Physiol, J Neurosci, Neurosci Lett, Rostral ventromedial medulla, Brain Res Rev, Nucleus raphe magnus, Morphine antinociception, Prog Neuropsychopharmacol Biol Psychiatry, Pharmacol Biochem Behav, J Pharm Pharmacol, Brain Res, Analgesic response, J Pharmacol Exp Ther, GABAergic interneuron, Internal cannula, J Neural Transm, Int J Neuropsychopharmacol.