Antinociceptive actions of descending dopaminergic tracts on cat and rat dorsal horn somatosensory neurones.
Antinociceptive actions of descending dopaminergic tracts on cat and rat dorsal horn somatosensory neurones.
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DOI：
10.1113/jphysiol.1988.sp017084
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发表时间：
1988-05
期刊：
影响因子：
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通讯作者：
S. Fleetwood-Walker;P. J. Hope;R. Mitchell
中科院分区：
文献类型：
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作者：
S. Fleetwood-Walker;P. J. Hope;R. Mitchell
1.在大鼠和猫脊髓背角分别应用多巴胺(DA)和DA受体特异性激动剂和拮抗剂，以及在脊髓上DA细胞群(A9和A11)局部电刺激对背角神经元的体感反应。被测试的神经元是多感受性的，对伤害性(使用机械挤压或辐射热)和无害(使用电动刷子)的皮肤刺激以及离子电泳法应用的DL-同型半胱氨酸(一种直接刺激剂)都能产生可重复的反应。在猫，所有被测试的神经元都被鉴定为属于脊髓颈束(SCT)，位于背角III-V层，而在大鼠，被测试的神经元位于脊髓丘脑束(STT)和脊髓中脑(SMT)，位于I层和III-V层。2.DA和D2DA受体激动剂RU24213可选择性抑制SCT、STT和SMT神经元对伤害性刺激的反应，而对非伤害性刺激的反应、自发活动和DLH诱发的活动无影响。这种作用在高选择性D2DA受体拮抗剂舒必利的存在下被逆转。单独应用舒必利和D1DA受体激动剂SKF38393都不能改变离子电泳法的诱发或自发活动。3.电刺激A11区选择性抑制大鼠脊髓多感受性神经元的伤害性反应，而不抑制A9、DA细胞群。在被测试的背角神经元附近，这种刺激诱发的效应被舒必利的离子导入持续而迅速地逆转。相比之下，纳洛酮和α2-受体拮抗剂咪唑克生(RX781094)无效。4.本研究的数据支持DA在脊髓水平对背角浅层和深层细胞具有广泛的抗伤害性影响的选择性抗伤害作用。结果表明，A11 DA细胞群是一个脊髓上部位，可从该部位电诱发选择性的抗伤害性反应，并由背角水平的DA介导。
1. The actions of dopamine (DA) and DA receptor specific agonists and antagonist ionophoretically applied in the spinal dorsal horn, and of focal electrical stimulation in the region of the supraspinal DA cell groups (A9 and A11) were assessed on the somatosensory responses of dorsal horn neurones, in both the rat and cat. The neurones tested were multireceptive, giving reproducible responses to both noxious (using a mechanical pinch or radiant heat) and innocuous (using a motorized brush) cutaneous stimuli, as well as to ionophoretically applied DL‐homocysteic acid (DLH, a direct excitant). In the cat, all neurones tested were identified as belonging to the spinocervical tract (SCT) and were located in the dorsal horn laminae III‐V, whilst in the rat, spinothalamic tract (STT) and spinomesencephalic (SMT) neurones located in the region of lamina I and laminae III‐V were tested. 2. Ionophoretically applied DA and RU24213, a D2 DA receptor agonist, caused a selective inhibition of the responses to noxious stimuli of SCT, STT and SMT neurones, whilst the responses to non‐nociceptive stimuli, spontaneous activity and DLH‐evoked activity were unaffected. This action was reversed in the presence of sulpiride, the highly selective D2 DA receptor antagonist. Neither sulpiride alone nor SKF38393, a D1 DA receptor agonist, altered evoked or spontaneous activity when ionophoretically applied. 3. Focal electrical stimulation in the region of the A11, but not the A9, DA cell group selectively suppressed nociceptive responses of spinal, multireceptive neurones in the rat. This stimulus‐evoked effect was consistently and rapidly reversed by ionophoresis of sulpiride, in the vicinity of the dorsal horn neurone being tested. In contrast, naloxone and idazoxan (RX781094), an alpha 2‐antagonist, were not effective. 4. This study presents data supporting a selective antinociceptive role for DA at the spinal level, where it has a widespread antinociceptive influence, on cells in both the superficial and deeper dorsal horn. The A11 DA cell group was shown to be a supraspinal site from which a selective antinociceptive action could be electrically evoked and which was mediated by DA at the level of the dorsal horn.