Pain
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Comparative Study
Synergistic interactions between two alpha(2)-adrenoceptor agonists, dexmedetomidine and ST-91, in two substrains of Sprague-Dawley rats.
Several lines of evidence indicate that the antinociception produced by intrathecal administration of the alpha(2)-adrenoceptor agonists dexmedetomidine or ST-91 is mediated by different subtypes of the alpha(2)-adrenoceptor. We recently provided additional pharmacologic evidence for this idea, as well as for differences in the function of these receptors between Harlan and Sasco rats, two widely-used outbred substrains of Sprague-Dawley rat. The present study used isobolographic analysis to further characterize the receptors at which intrathecally administered ST-91 and dexmedetomidine act in these two substrains. ⋯ This conclusion is consistent with the earlier proposal that dexmedetomidine acts predominantly at alpha(2A)-adrenoceptors whereas ST-91 acts predominantly at non-alpha(2A)-adrenoceptors. Recent anatomical evidence indicates that these non-alpha(2A) adrenoceptors may be of the alpha(2C) type. The synergistic combination of an alpha(2A)- and an alpha(2C)-adrenoceptor agonist may provide a unique and highly effective drug combination for the treatment of pain without the sedation produced by an equianalgesic dose of a single alpha(2)-adrenoceptor agonist.
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It has been shown that women have a lower pain threshold and lower tolerance to some forms of experimental pain then men. However, the evidence that clinical pain is perceived differently by the two sexes is not yet as strong. The placement of intraoral implants is a highly controlled surgical procedure that we have used to investigate this possibility. ⋯ Males and females did not differ in the total number of words chosen from the MPQ (P=0.61), or in the averaged Pain Rating Index (PRI) (P=0.53). However, women used significantly more evaluative words than men (P=0.04), suggesting that woman found the overall intensity greater. These results indicate that women find post-surgical pain more intense than males, but that men are more disturbed than women by low levels of pain that last several days.
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The omega-conopeptide, ziconotide, is an N-type calcium-channel blocker that has been shown to produce antinociception in animals using formalin and hot-plate tests. Initial reports of intrathecal administration of ziconotide in cancer and AIDS patients whose pain was unrelieved with opioids demonstrated analgesic efficacy. Although adverse effects were reported, these appeared to be easily managed through dose reduction or symptomatic treatment. This clinical report describes the experiences of three patients with serious adverse effects associated with intrathecal ziconotide.
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Intensity dependence of auditory evoked cortical potentials is abnormal in migraine. This study investigated intensity dependence in migraine and healthy families using group comparisons and analysis of individual differences. Migraineurs were characterized by a steeper amplitude/stimulus function slope and more pronounced difference between the amplitudes of N1-P2 on the more and the less intensive tones than healthy age matched subjects. ⋯ Familial prevalence of intensity dependence among first-degree relatives in migraine families was equal to that in healthy families. These findings support the assumption that high-intensity dependence reflects a functional CNS trait which is more pronounced and prevalent in migraine, but may also be found in healthy individuals and in other neuropsychiatric disorders. Increased intensity dependence is only one of several factors contributing to the risk for this form of headache.
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The study of neonatal gender differences in pain expression is important since neonatal pain behavior occurs prior to any learned reaction pattern. The objective of this study was to verify the presence of gender differences in pain expression in preterm and term newborn infants. Sixty-five consecutive neonates (37 female and 28 male infants) with gestational age between 28 and 42 weeks and with 25-120 h of life were studied. ⋯ No significant interactions between gestational age and time, nor between gestational age and gender were noted, for both NFCS and NIPS. In conclusion, recently born female neonates of all gestational ages expressed more facial features of pain than male infants, during the capillary puncture and 1 min afterwards. Maybe differences in pain processing and/or pain expression among genders may explain this finding.