Park J S, Nakatsuka T, Nagata K, Higashi H, Yoshimura M
Department of Physiology, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan.
Brain Res Dev Brain Res. 1999 Mar 12;113(1-2):29-36. doi: 10.1016/s0165-3806(98)00186-2.
To study the reorganization of the primary afferent input in the spinal dorsal horn during post-natal development, synaptic responses evoked by large Abeta and fine Adelta afferents were recorded from substantia gelatinosa (SG) neurons in slices obtained from immature (post-natal days 21-23) and mature rats (post-natal days 56-60). Threshold stimulus intensities and conduction velocities (CVs) of Abeta and Adelta afferents were determined by intracellular recordings of the antidromic action potentials from dorsal root ganglion (DRG) neurons isolated from immature and mature rats. In immature rats, excitatory postsynaptic currents (EPSCs) were elicited by stimulation sufficient to activate Abeta afferents in the majority of SG neurons (64.9%, 24 of 37 neurons), while most EPSCs observed in mature rats were elicited by stimulation of Adelta afferents (62.5%, 25 of 40 neurons). These observations suggest that the primary afferents innervating SG neurons were reorganized following maturation; Abeta afferents were the predominant inputs to the SG neurons in the immature state, thereafter Adelta afferents were substituted for the Abeta afferents to convey sensory information to the SG neurons. This relatively slow reorganization of the sensory circuitry may correlate with slow maturation of the SG neurons and with a delay in the functional connections of C afferents to the SG neurons.
为研究出生后发育过程中脊髓背角初级传入输入的重组，在从新生（出生后21 - 23天）和成年大鼠（出生后56 - 60天）获取的切片中，记录了来自胶状质（SG）神经元的由粗大的Aβ和细小的Aδ传入纤维诱发的突触反应。通过对从新生和成年大鼠分离的背根神经节（DRG）神经元的逆行动作电位进行细胞内记录，测定了Aβ和Aδ传入纤维的阈刺激强度和传导速度（CV）。在新生大鼠中，大多数SG神经元（64.9%，37个神经元中的24个）通过足以激活Aβ传入纤维的刺激诱发兴奋性突触后电流（EPSC），而在成年大鼠中观察到的大多数EPSC是由刺激Aδ传入纤维诱发的（62.5%，40个神经元中的25个）。这些观察结果表明，支配SG神经元的初级传入纤维在成熟后发生了重组；在未成熟状态下，Aβ传入纤维是SG神经元的主要输入，此后Aδ传入纤维取代Aβ传入纤维向SG神经元传递感觉信息。这种感觉神经回路相对缓慢的重组可能与SG神经元的缓慢成熟以及C传入纤维与SG神经元功能连接的延迟有关。
