Molnar M, Casini G, Davis B M, Bagnoli P, Brecha N C
Department of Physiology and Biochemistry, University of Pisa, Italy.
J Comp Neurol. 1994 Oct 15;348(3):419-32. doi: 10.1002/cne.903480308.
Bioassay and immunological studies have detected the presence of opioid peptides in the nervous system of representatives of all classes of vertebrates. The present study evaluates the expression and localization of preproenkephalin (PPE) mRNA to determine the sites of synthesis of the enkephalin peptides in the adult chicken and pigeon telencephalon using in situ hybridization histochemistry. We used a 500-base-pair chicken RNA probe corresponding to chicken PPE cDNA. In both the chicken and the pigeon telencephalon, the highest concentration of PPE mRNA-containing cells was observed in the lobus parolfactorius, paleostriatum augmentatum, nucleus accumbens, and septum. Distinct populations of labeled cells were also detected in the hyperstriatum accessorium, hippocampus, area parahippocampalis, nucleus of the diagonal band, cortex dorsolateralis, and cortex piriformis. Differences in PPE mRNA expression between chicken and pigeon were observed in several telencephalic regions. For instance, the bulbus olfactorius was heavily labeled in the pigeon, but was not labeled in the chicken, and numerous PPE mRNA-containing cells were present in the area parahippocampalis of pigeons but not of chickens. In contrast, in the hyperstriatum dorsale and hyperstriatum ventrale, numerous PPE mRNA-expressing cells were detected in the chicken but not in the pigeon. Overall, PPE mRNA-expressing cells were more numerous than enkephalin-immunoreactive cells described in previous studies. In addition, our results suggest that the general pattern of enkephalin expression in the avian telencephalon is similar to that found in other vertebrates. Finally, the results of the present study illustrate some differences in the pattern of PPE mRNA distribution between closely related species, indicating the existence of species-specific neurochemical pathways, which may influence and perhaps mediate different behaviors characteristics of these species.
生物测定和免疫学研究已在所有脊椎动物类别的代表的神经系统中检测到阿片肽的存在。本研究使用原位杂交组织化学评估前脑啡肽原（PPE）mRNA的表达和定位，以确定成年鸡和鸽端脑中脑啡肽肽的合成部位。我们使用了与鸡PPE cDNA对应的500个碱基对的鸡RNA探针。在鸡和鸽的端脑中，在嗅旁叶、增大旧纹状体、伏隔核和隔区观察到含PPE mRNA细胞的最高浓度。在副嗅球、海马、海马旁区域、斜角带核、背外侧皮质和梨状皮质中也检测到不同的标记细胞群。在几个端脑区域观察到鸡和鸽之间PPE mRNA表达的差异。例如，嗅球在鸽中被大量标记，但在鸡中未被标记，并且在鸽的海马旁区域存在大量含PPE mRNA的细胞，而鸡中则没有。相反，在背侧新纹状体和腹侧新纹状体中，在鸡中检测到大量表达PPE mRNA的细胞，而在鸽中未检测到。总体而言，表达PPE mRNA的细胞比先前研究中描述的脑啡肽免疫反应性细胞更多。此外，我们的结果表明，鸟类端脑中脑啡肽表达的总体模式与在其他脊椎动物中发现的模式相似。最后，本研究结果说明了密切相关物种之间PPE mRNA分布模式的一些差异，表明存在物种特异性神经化学途径，这可能影响并可能介导这些物种的不同行为特征。
