Pain
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Processing of nociceptive information can be modulated at various levels in spinal cord that may range from changes of neurotransmitter release from primary afferent Adelta- or C-fibres to excitability changes of spinal interneurones or motoneurones. The site and mechanism of action of spinal analgesics has been assessed with a number of in vivo and in vitro methods with sometimes conflicting results. ⋯ Polysynaptic responses were dose-dependently inhibited while the monosynaptic response remained unaffected. These results suggest that spinal analgesics may preferentially affect polysynaptic but not monosynaptic Adelta-fibre-evoked responses in superficial spinal dorsal horn.
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The anticonvulsant gabapentin is effective against neuropathic pain, but the primary site(s) and mechanism(s) of action are unknown. In order to explore the relative contribution of spinal versus supra-spinal mechanisms to the antinociceptive effect of gabapentin, this study used two differentially integrated nociceptive tests. We systematically compared the effects of various doses of gabapentin on the paw withdrawal to pressure (PWTP), a spinally coordinated reflex and the vocalization threshold to paw pressure (VTPP), a supra-spinal integrated test in the sciatic nerve constriction rat model of neuropathic pain. ⋯ Gabapentin at 100 mg/kg but not at 30 mg/kg produced motor deficits in animals using the rotarod test. Taken together, our findings suggest that low doses of gabapentin have a preferential action on the more integrated pain-related behaviour in neuropathic rats. The present results confirm that gabapentin may be a useful approach for the clinical management of several aspects of neuropathic pain.
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Studies have shown that the steroid anaesthetic alphaxalone positively modulates gamma-aminobutyric acid (GABA) receptors in vitro. It has also been reported that positive modulation of GABA(A) receptors in the rat spinal cord can produce antinociception in vivo. This present study looks at the interaction of an intraperitoneal injection (i.p.) of the steroid anaesthetic combination Saffan (alphaxalone 9 mg/ml, alphadolone acetate 3 mg/ml) with GABA(A) receptors in the spinal cord. ⋯ Alphadolone caused no sedation but it did cause antinociceptive effects equal in magnitude to those produced by Saffan. We conclude that Saffan produces antinociception in rats when given i.p. by an interaction with spinal GABA(A) receptors. Furthermore, this antinociception is due to the alphadolone content of the neurosteroid anaesthetic and not the alphaxalone.
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Chronic pain, lymphoedema, post-irradiation neuropathy and other symptoms are reported in as many as 75% of women following breast cancer treatment. This study examined pain and sensory abnormalities in women following breast cancer surgery. Sensory tests were carried out on operated and contralateral sides in 15 women with spontaneous pain and sensory abnormalities and 11 pain-free women. ⋯ Pinprick-evoked pain was correlated to spontaneous pain but not to flux. Spontaneous pain was not correlated to flux. Sensitization seems to be a feature in breast cancer-operated women with pain, but not in pain-free women.
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One hundred and sixty-eight patients with osteoarthritis (OA) of the knees participated in this study. Of the participants, 72 were men and 96 were women. All participants completed the Arthritis Impact Measurement Scales (AIMS), underwent a 10 min standardized observation session to assess their pain behavior, and completed the Catastrophizing Scale of the Coping Strategies Questionnaire (CSQ) and the Depression Scale of the Symptom Checklist 90 Revised (SCL-90R). ⋯ Once catastrophizing was entered into the analyses, the previously significant effects of gender were no longer found. Interestingly, catastrophizing still mediated the gender-pain relationship even after controlling for depression. These findings underscore the importance of both gender and catastrophizing in understanding the OA pain experience and may have important implications for pain assessment and treatment.