The Mina and Everard Goodman Faculty of Life Sciences and The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar Ilan University, Ramat Gan, Israel.
J Neurophysiol. 2011 Apr;105(4):1642-50. doi: 10.1152/jn.00827.2010. Epub 2011 Jan 27.
An increase in L-arginine hemolymph concentration acts as a postingestion signal inhibiting Aplysia feeding. At physiological concentrations (a 10-μM increase over background), the inhibitory effect of L-arginine is too weak to block feeding in hungry animals. However, a 10-μM increase in L-arginine concentration acts along with another inhibitory stimulus, the sustained presence of food odor, to inhibit feeding after a period of access to food. A physiological concentration of L-arginine also blocked the excitatory effect of a stimulus enhancing feeding, pheromones secreted by mating conspecifics. High concentrations of L-arginine (2.5 mM) alone also inhibited ad libitum feeding. L-arginine is the substrate from which nitric oxide synthase (NOS) produces nitric oxide (NO). Both an NO donor and a 10-μM increase in L-arginine inhibited biting in response to a weak food stimulus. Treatment with NOS inhibitors initiated food-finding and biting in the absence of food, indicating that food initiates feeding against a background of tonic nitrergic inhibition. Increased feeding in response to blocking NOS is accompanied by firing of the metacerebral (MCC) neuron, a monitor of food arousal. The excitatory effect on the MCC of blocking NOS is indirect. The data suggest that L-arginine acts by amplifying NO synthesis, which acts as a background stimulus inhibiting feeding. Background modulation of neural activity and behavior by NO may also be present in other systems, but such modulation may be difficult to identify because its effects are evident only in the context of additional stimuli modulating behavior.
血液中精氨酸浓度的增加会发出抑制进食的信号。在生理浓度（比背景浓度高 10 微摩尔）下，精氨酸的抑制作用太弱，无法阻止饥饿动物进食。然而，血液中精氨酸浓度增加 10 微摩尔，再加上另一个抑制性刺激，即持续存在的食物气味，会在一段时间接触食物后抑制进食。生理浓度的精氨酸也会阻断刺激增强进食的效应，即同种交配个体分泌的信息素。高浓度的精氨酸（2.5 毫摩尔）本身也会抑制随意进食。精氨酸是一氧化氮合酶（NOS）产生一氧化氮（NO）的底物。一氧化氮供体和血液中精氨酸增加 10 微摩尔都能抑制对弱食物刺激的咬食反应。NOS 抑制剂的处理在没有食物的情况下引发觅食和咬食，表明食物在持续的紧张性氮能抑制背景下引发进食。阻断 NOS 引起的进食增加伴随着大脑中部（MCC）神经元的放电，这是食物唤醒的监测器。阻断 NOS 对 MCC 的兴奋作用是间接的。这些数据表明，精氨酸通过放大 NO 合成来发挥作用，NO 作为一种背景刺激抑制进食。NO 对神经活动和行为的背景调节也可能存在于其他系统中，但这种调节可能难以识别，因为只有在调节行为的其他刺激的背景下，其影响才明显。
