Burd G D, Davis B J, Macrides F, Grillo M, Margolis F L
J Neurosci. 1982 Feb;2(2):244-55. doi: 10.1523/JNEUROSCI.02-02-00244.1982.
Previous in vivo studies have shown that beta-alanine is incorporated specifically into the dipeptide L-carnosine (beta-alanyl-L-histidine). In the present study, we administered beta-[3H]alanine to the nasal cavity of hamsters and used biochemical analyses to identify the radioactively labeled compounds in the olfactory epithelium and olfactory bulb and autoradiography to demonstrate the localization and transport of the label in the primary afferents of the olfactory system. The olfactory epithelium and lamina propria were labeled intensely 6 hr after intranasal beta-[3H]alanine administration. At this survival time, 61% of the radioactivity in the olfactory epithelium was present in the carnosine fraction, while 37% of the label remained in the beta-alanine fraction. After 24-hr and 4-day survival periods, greater than 82% of the radioactivity was present in the carnosine fraction, and the olfactory receptors and bundles of axons were labeled preferentially. The olfactory nerve and glomerular layers of the main olfactory bulb were labeled intensely at 6 and 24 hr after beta-[3H]alanine administration; much less label was present in these layers at 4 days survival. At all three of these survival times, greater than 84% of the radioactivity in the olfactory bulb was present in the carnosine fraction. No label was present in the olfactory epithelium or bulb 18 days after beta-[3H]alanine administration. While the autoradiographic labeling over the structures of the accessory olfactory system was consistently less intense than that over the main olfactory system structures, the patterns of labeling were similar over the four survival times. Intranasal alpha-[3H]alanine administration resulted in some labeling in the primary afferent fibers, but the labeling did not have the specificity nor the same time course over the four survival times that was observed after beta-[3H]alanine administration. The results are consistent with the hypothesis that carnosine is a neurotransmitter or neuromodulator in the olfactory neurons. The results also suggest that carnosine may play a similar role in the vomeronasal neurons.
以往的体内研究表明，β-丙氨酸可特异性地掺入二肽L-肌肽（β-丙氨酰-L-组氨酸）中。在本研究中，我们将β-[3H]丙氨酸注入仓鼠鼻腔，并通过生化分析来鉴定嗅上皮和嗅球中放射性标记的化合物，同时利用放射自显影技术来证明标记物在嗅觉系统初级传入神经中的定位和转运。鼻内给予β-[3H]丙氨酸6小时后，嗅上皮和固有层被强烈标记。在此存活时间，嗅上皮中61%的放射性存在于肌肽部分，而37%的标记物仍留在β-丙氨酸部分。在24小时和4天的存活期后，超过82%的放射性存在于肌肽部分，并且嗅觉受体和轴突束被优先标记。给予β-[3H]丙氨酸后6小时和24小时，主嗅球的嗅神经层和肾小球层被强烈标记；在4天存活时，这些层中的标记物要少得多。在所有这三个存活时间，嗅球中超过84%的放射性存在于肌肽部分。给予β-[3H]丙氨酸18天后，嗅上皮或嗅球中没有标记物。虽然副嗅觉系统结构上的放射自显影标记始终比主嗅觉系统结构上的标记弱，但在四个存活时间内的标记模式相似。鼻内给予α-[3H]丙氨酸会导致初级传入纤维有一些标记，但这种标记在四个存活时间内没有β-[3H]丙氨酸给药后所观察到的特异性和相同的时间进程。这些结果与肌肽是嗅觉神经元中的神经递质或神经调节剂这一假设一致。结果还表明，肌肽可能在犁鼻神经元中发挥类似作用。
