Vaupel D B, Martin W R
J Pharmacol Exp Ther. 1976 Jan;196(1):87-96.
The effects of norepinephrine, methoxamine and tryptamine were assessed on the monosynaptic and polysynaptic segmental reflexes in the unanesthetized, decerebrated acute spinal cat. Their selectivity of action was determined by studying the interactions of methoxamine and tryptamine with two antagonists, cyproheptadine and phenoxybenzamine. Potentials were evoked by stimulating either the L7 or S1 dorsal root and were recorded from the corresponding ipsilateral ventral root. Norepinephrine did not affect reflex activity, whereas methoxamine facilitated both the monosynaptic and polysynaptic potentials in a dose-related manner when infused over 20 minutes. Tryptamine facilitated both the monosynaptic and polysynaptic reflex potentials. This increase was dose related for the monosynaptic reflex but not for the polysynaptic reflex. Phenoxybenzamine blocked the facilitatory effects of methoxamine and did not antagonize the effects of tryptamine on the segmental reflex. The facilitatory effects of tryptamine were effectively blocked by cyproheptadine. Cyproheptadine failed to reduce the polysynaptic response to methoxamine, although it partially antagonized the monosynaptic facilitation. These findings demonstrate that methoxamine and tryptamine facilitate the segmental reflex by different modes of action and provide additional evidence for noradrenergic and tryptaminergic systems in the spinal cord.
在未麻醉、去大脑的急性脊髓猫身上，评估了去甲肾上腺素、甲氧明和色胺对单突触和多突触节段性反射的影响。通过研究甲氧明和色胺与两种拮抗剂赛庚啶和酚苄明的相互作用，确定了它们的作用选择性。通过刺激L7或S1背根诱发电位，并从相应的同侧腹根记录。去甲肾上腺素不影响反射活动，而在20分钟内注入甲氧明时，它以剂量相关的方式促进单突触和多突触电位。色胺促进单突触和多突触反射电位。这种增加与单突触反射呈剂量相关，但与多突触反射无关。酚苄明阻断了甲氧明的促进作用，并且不拮抗色胺对节段性反射的作用。赛庚啶有效地阻断了色胺的促进作用。尽管赛庚啶部分拮抗了单突触促进作用，但它未能降低对甲氧明的多突触反应。这些发现表明，甲氧明和色胺通过不同的作用方式促进节段性反射，并为脊髓中的去甲肾上腺素能和色胺能系统提供了额外的证据。
