大鼠运动皮层来自胼胝体的同位和异位神经元

HOMOTOPIC AND HETEROTOPIC CALLOSAL NEURONS TO RAT MOTOR CORTEX

实验的目的是用HRP逆行追踪法研究投射至大鼠运动皮层的胼胝体神经元的形态和分布。将HRP注射到大鼠一侧运动皮层后 ,对侧运动皮层中逆行标记的胼胝体神经元为中等大小的锥体细胞 ,分布于II/III、V和VI层 ,其中V、VI层的细胞较为宽、大 ;计算机辅助三维重构的图象显示了注射部位和标记部位有很好的对应投射关系。此外 ,还首次观察到对侧眶回 (外侧和腹外侧 )向运动皮层的投射 ,这些位于眶回深层的胼胝体神经元较小而扁 ,且这种异位起源有投射区域的特异性 ;仅投向Frl的前端 (触须和鼻缘的代表区 ) ,而不向Fr3 (爪、唇和舌的代表区 )。这些同位和异位胼胝体起源提示了在大鼠的运动功能和其发达的嗅觉之间可能的内在联系。

To study the distribution and morphological fectures of callosal neurons to rat motor cortex Methods:HRP retrograde technique was used Results:Single or multiple injection(s) of HRP into rat motor cortex resulted in retrogradely labeled pyramidal cells in layer II/III and layer V-VI of contralateral motor cortex.These homotopic callosal neurons were small or medium pyramidal cells with those in layer V-VI wider and larger.Computer-assisted three-dimensional reconstruction of rat brain showed an exact point to point feature of callosal projection in rat motor cortex.Furthermore,Some HRP-labeled neurons were also observed in the deep layer of the lateral and ventrolateral parts in contralateral orbital cortex.Compared to the homotopic callosal neurons observed in motor cortex,these orbital hetrotopic callosal neurons were shorter and wider.Interestingly,such orbital heterotopic callosal projections were selectively destined to the anterior part of Fr1 (representations for vibrissae and rhinarium) rather than Fr3 (representations for jaw,lip and tongue,).Conclusion:In addition to the homotopic origin,callosal projections to rat motor cortex also derive .from the orbital cortex.suggesting possible functional relevance between movement and the strong olfactory function in rats