味觉刺激引起大鼠臂旁核神经元抑制性反应

本研究以轻度麻醉的大鼠为对象,应用细胞外微电极记录技术,观察并分析了脑桥臂旁核抑制性味觉神经元的自发活动及其对NaCl、HCl、盐酸奎宁（quinine HCl,QHCl））和蔗糖等四种基本味觉刺激的反应。共分析了18个具有自发活动的抑制性味觉神经元,自发放电频率分布在0．2～5．5Hz之间,平均放电频率（2．15±0．31）Hz。18个神经元中,1个神经元对单一味觉刺激呈抑制性反应,其余17个神经元对两种或两种以上的基本味觉刺激发生抑制性反应,且抑制具有潜伏期短、持续时间较长等特征。抑制持续时间5～80S,部分神经元表现为后抑制效应。根据神经元对四种基本味觉刺激呈抑制性反应的程度,将其分为NaCl优势神经元（n=8）,HCl优势神经元（n=3）,QHCl优势神经元n=3）和蔗糖优势神经元n=4）。其中NaCl优势神经元的反应谐宽最高（0．945）。这些神经元对欣快或厌恶刺激的区别能力较低。结果提示,在脑桥臂旁核存在对味觉刺激起抑制性反应的神经元,这些味觉神经元可能在味觉的调制及对欣快和厌恶刺激的编码中发挥重要的作用。

Inhibitory responses of parabrachial neurons evoked by taste stimuli in rat

In the present study, the responses of inhibitory gustatory neurons in the parabrachial nucleus (PBN) to four basic taste stimuli NaCl, HCl, quinine HCl (QHCl) and sucrose were examined using single-unit recording technique in anesthetized rats. A total of 18 inhibitory taste neurons in the PBN were obtained. Spontaneous firing rates of these inhibitory neurons were 0.2-5.5 Hz with mean firing rate of (2.15+/-0.31) Hz. Most of the neurons responded to more than one of the basic taste qualities. The inhibitory responses to taste occurred quickly and lasted 5-80 s in different PBN neurons. According to the responsive characteristics to the four basic taste stimuli, the neurons could be classified as NaCl-best (n=8), HCl-best (n=3), QHCl-best (n=3), and sucrose-best (n=4). The breadth of tuning of NaCl-best neurons was the highest (0.945). Inhibitory responsive neurons had feeble discrimination among sapid stimuli or aversive stimuli. These results suggest that there exist inhibitory taste neurons in the PBN. These neurons may play some useful roles in precise transmission of taste information and the taste coding for hedonic and aversive tastes.