Somatosensory information can be modulated at the spinal cord level by primary afferent depolarization (PAD), known to produce presynaptic inhibition (PSI) by decreasing neurotransmitter release through the activation of presynaptic ionotropic receptors. Descending monoaminergic systems also modulate somatosensory processing. We investigated the role of D₁-like and D₂-like receptors on pathways mediating PAD in the hemisected spinal cord of neonatal mice. We recorded low-threshold evoked dorsal root potentials (DRPs) and population monosynaptic responses as extracellular field potentials (EFPs). We used a paired-pulse conditioning-test protocol to assess homosynaptic and heterosynaptic depression of evoked EFPs to discriminate between dopaminergic effects on afferent synaptic efficacy and/or on pathways mediating PAD, respectively. DA (10 μM) depressed low-threshold evoked DRPs by 43 %, with no effect on EFPs. These depressant effects on DRPs were mimicked by the D₂-like receptor agonist quinpirole (35 %). Moreover, by using selective antagonists at D₂-like receptors (encompassing the D₂, D₃, and D₄ subtypes), we found that the D₂ and D₃ receptor subtypes participate in the quinpirole depressant inhibitory effects of pathways mediating PAD.

体感信息可以通过初级传入去极化 (PAD) 在脊髓水平进行调节，已知通过激活突触前离子型受体减少神经递质释放来产生突触前抑制 (PSI)。下降的单胺能系统也调节体感处理。我们调查d的作用，₁ -像和d ₂ -样新生小鼠半切脊髓中介导 PAD 通路上的受体。我们将低阈值诱发背根电位 (DRP) 和群体单突触反应记录为细胞外场电位 (EFP)。我们使用配对脉冲调节测试方案来评估诱发 EFP 的同突触和异突触抑制，以分别区分多巴胺能对传入突触功效和/或介导 PAD 的通路的影响。DA (10 μM) 将低阈值诱发的 DRP 降低了 43%，对 EFP 没有影响。上DRPS这些抗抑郁作用被模仿d ₂ -样受体激动剂喹吡罗（35％）。此外，通过使用选择性拮抗剂在d ₂ -样受体（包围d ₂、D ₃和D ₄亚型），我们发现D ₂和D ₃受体亚型参与介导PAD 通路的喹吡罗抑制作用。