Tsuneyoshi Yousuke, Tomonaga Shozo, Asechi Mari, Morishita Koji, Denbow D Michael, Furuse Mitsuhiro
Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan.
BMC Neurosci. 2007 May 31;8:37. doi: 10.1186/1471-2202-8-37.
Carnosine (beta-alanyl-L-histidine) is a putative neurotransmitter and has a possible role in neuron-glia cell interactions. Previously, we reported that carnosine induced hyperactivity in chicks when intracerebroventricularly (i.c.v.) administered. In the present study, we focused on other beta-alanyl dipeptides to determine if they have novel functions.
In Experiment 1, i.c.v. injection of beta-alanyl-L-leucine, but not beta-alanyl-glycine, induced hyperactivity behavior as observed with carnosine. Both carnosine and beta-alanyl-L-leucine stimulated corticosterone release. Thus, dipeptides of beta-alanyl-branched chain amino acids were compared in Experiment 2. The i.c.v. injection of beta-alanyl-L-isoleucine caused a similar response as beta-alanyl-L-leucine, but beta-alanyl-L-valine was somewhat less effective than the other two dipeptides. beta-Alanyl-L-leucine strongly stimulated, and the other two dipeptides tended to stimulate, corticosterone release.
These results suggest that central beta-alanyl-branched chain amino acid stimulates activity in chicks through the hypothalamus-pituitary-adrenal axis. We named beta-alanyl-L-leucine, beta-alanyl-L-isoleucine and beta-alanyl-L-valine as Excitin-1, Excitin-2 and Excitin-3, respectively.
肌肽（β-丙氨酰-L-组氨酸）是一种假定的神经递质，在神经元-神经胶质细胞相互作用中可能发挥作用。此前，我们报道了脑室内（i.c.v.）注射肌肽会使雏鸡出现多动行为。在本研究中，我们聚焦于其他β-丙氨酰二肽，以确定它们是否具有新功能。
在实验1中，脑室内注射β-丙氨酰-L-亮氨酸会诱导出与肌肽注射时观察到的类似的多动行为，而β-丙氨酰甘氨酸则不会。肌肽和β-丙氨酰-L-亮氨酸均能刺激皮质酮释放。因此，在实验2中对β-丙氨酰支链氨基酸的二肽进行了比较。脑室内注射β-丙氨酰-L-异亮氨酸引起的反应与β-丙氨酰-L-亮氨酸相似，但β-丙氨酰-L-缬氨酸的效果略逊于其他两种二肽。β-丙氨酰-L-亮氨酸强烈刺激皮质酮释放，并促使其他两种二肽也有刺激皮质酮释放的趋势。
这些结果表明，中枢β-丙氨酰支链氨基酸通过下丘脑-垂体-肾上腺轴刺激雏鸡的活动。我们分别将β-丙氨酰-L-亮氨酸、β-丙氨酰-L-异亮氨酸和β-丙氨酰-L-缬氨酸命名为兴奋素-1、兴奋素-2和兴奋素-3。
