Articles: hyperalgesia.
-
Chronic pain in adults has been associated with early-life stress. To examine the pronociceptive effect of early-life stress, we evaluated cutaneous and muscle nociception and activity in muscle nociceptors in an animal model of neonatal stress, limited bedding, in the rat. In this neonatal limited bedding (NLB) model, litters are exposed to limited bedding between postnatal days 2 and 9, and controls to standard bedding. ⋯ Furthermore, administration of prostaglandin E(2) in skin as well as muscle produced markedly prolonged hyperalgesia, an effect prevented by spinal intrathecal injection of oligodeoxynucleotide antisense to protein kinase Cε (PKCε), a second messenger in nociceptors that has been implicated in the induction and maintenance of chronic pain. In electrophysiological studies, mechanical threshold of muscle nociceptors was reduced by ~31% and conduction velocity significantly increased (~28%). These findings indicate that neonatal stress induces a persistent hyperalgesia and nociceptor sensitization manifest in the adult and that the second messenger PKCε may be a target against which therapies might be directed to treat a chronic pain syndrome that is associated with early-life traumatic stress.
-
Whether schizophrenic patients are hypoalgesic or feel pain in the same manner as unaffected individuals can affect the primary care of schizophrenic patients, which often involves an assessment of pain severity made by a medical provider. This study was developed to explore the pain sensitivity of schizophrenics under conditions similar to those of a medical examination that included investigating for sites of pain. ⋯ Under these conditions, schizophrenic patients were hypersensitive to pain induction compared with normal individuals. The hypoalgesia typically associated with schizophrenic patients may correspond to fewer than normal reports of pain, rather than to impaired sensations of pain. This should be taken into account during routine medical practice.
-
Pharmacol. Biochem. Behav. · Nov 2011
Comparative StudyAntinociceptive effects of intragastric DL-tetrahydropalmatine on visceral and somatic persistent nociception and pain hypersensitivity in rats.
Although tetrahydropalmatine (THP), an alkaloid constituent of plants from the genera Stephania and Corydalis, is known to have analgesic property, the antinociceptive effects of THP have not been well evaluated experimentally and the appropriate indications for treatment of clinical pain remain unclear. In the present study, nociceptive and inflammatory models of both somatic and visceral origins were used to assess the antinociceptive and antihyperalgesic effects of intragastric (i.g.) pretreatment of dl-THP in rats. In the bee venom (BV) test that has been well established experimentally, i.g. pretreatment of three doses of dl-THP (20, 40, 60 mg/kg, body weight) resulted in less stably antinociceptive effect on the BV-induced persistent paw flinches that are known to be processed by spinal nociceptive circuit, however the drug of the two higher doses produced distinct suppression of the BV-induced persistent nociception rated by nociceptive score that reflects both spinal and supraspinal mediation. ⋯ In the acetic acid writhing test, the number of writhes was completely blocked at the first 5-min interval followed by a sustained suppression in the remaining period of the whole time course comparing to the vehicle control. These data suggest that i.g. pre-administration of dl-THP could more effectively inhibit visceral nociception as well as thermal and mechanical inflammatory pain hypersensitivity (hyperalgesia) than persistent nociception. Moreover, the drug is likely to produce more effectiveness on supraspinally processed nociceptive behaviors than spinally mediated nociceptive behaviors, implicating an action of THP at the supraspinal level.
-
Human immunodeficiency virus (HIV)-related distal sensory polyneuropathy (DSP) is the most common HIV-associated sensory neuropathy. The envelope glycoprotein of HIV-1, gp 120, appears to contribute to this painful neuropathy. Two standard treatments for HIV infection/HIV-related painful DSP (e.g., antiviral therapy [e.g., nucleoside reverse transcriptase inhibitors (NRTI)] opioids) should each be carefully evaluated prior to being utilized to ameliorate the pain of DSP, since they may actually promote nociception. Nucleoside reverse transcriptase inhibitors require activation in the cell via the addition of 3 phosphate groups (by cellular kinases) to their deoxyribose moiety, to form NRTI triphosphates. Subsequently, these deoxynucleotide analogs compete with natural deoxynucleotides for incorporation into the growing viral DNA chain. The incorporation of NRTIs into the viral DNA chain leads to chain termination; since the nucleoside reverse transcriptase inhibitors lack a 3'-hydroxyl group on the deoxyribose moiety (unlike natural deoxynucleotides), so that the next incoming deoxynucleotide cannot form the next 5'-3' phosphodiester bond needed to extend the DNA chain. Unfortunately, many conventional agents utilized as pharmacologic therapy for neuropathic pain are not effective for providing satisfactory analgesia in painful HIV-related distal sensory polyneuropathy. Although there is no robust data, there does seem to be information which would support the notion of opioids having increased risk of being particularly pronociceptive when being used to treat painful HIV-related neuropathy. It thus appears conceivable that the use of at least certain opioids in efforts to achieve analgesia in patients with painful HIV-related neuropathy may be less than ideal since at least certain opioid analgesics themselves may potentially contribute to "fueling the fire" of HIV enhanced pain hypersensitivity; at least in part via upregulation of specific chemokine receptors (e.g., CXCR4) which seem to be vitally important in promoting HIV-related pain facilitation. The risk benefit ratio of treatment with agents such as NRTIs as well as opioids should be reviewed for specific individual patients, prior to clinicians initiating these agents. ⋯ Clinicians should consider all aspects of various therapeutic options, carefully weighing the risk/benefit ratios of each potential treatment before initiating opioids for painful HIV-related neuropathy.