Ogawa H, Hasegawa K, Ohgushi M, Murayama N
Department of Physiology, Kumamoto University Medical School, Japan.
Neurosci Res. 1994 Jun;19(4):407-17. doi: 10.1016/0168-0102(94)90082-5.
Changes in the features of responses of cortical taste neurons were studied in granular insular (GI) and dysgranular insular (DI) areas of urethane-anesthetized SD rats of four age groups (4-10, 14-20, 25-35 and > 90 days). Stimuli included four basic taste stimuli, 0.1 M NH4Cl, and the water extract of a food pellet, applied to the entire oral cavity. At the age of 4-10 days, taste neurons showed no spontaneous discharge, and most responded to NH4Cl in a phasic fashion. In older age groups, however, there was a spontaneous discharge, and tonic taste responses were evident; some responded better to the four basic stimuli and to the food than to NH4Cl. With only a few days' difference in age, inhibitory responses were also noted in both areas. Average taste responses increased or decreased at different ages, depending on the type of taste stimulus and recording area. When taste responses were plotted against the four basic taste stimuli in the order of sucrose, NaCl, HCl and quinine along the abscissa, some neurons showed double-peaked response profiles. This suggests the convergence and mutual inhibition of afferents at single cortical neurons. The fraction of neurons with double-peaked response profiles increased at the age of 25-35 days in both areas. Neurons in rats aged 25-35 days were predominantly sensitive to either NH4Cl or NaCl, or to either food or sucrose. Neurons in rats of other ages, during the preweanling and the adult stages, tended to respond to both these stimuli. Our observations suggest that cortical taste neurons develop in the rat brain in accordance with the maturation of both the taste receptors and the neural networks.
在四个年龄组（4 - 10天、14 - 20天、25 - 35天和大于90天）的氨基甲酸乙酯麻醉的SD大鼠的颗粒状岛叶（GI）和颗粒减少的岛叶（DI）区域，研究了皮质味觉神经元反应特征的变化。刺激包括四种基本味觉刺激、0.1M氯化铵以及食物颗粒的水提取物，施加于整个口腔。在4 - 10天龄时，味觉神经元无自发放电，且大多数对氯化铵呈相位性反应。然而，在年龄较大的组中，存在自发放电，且紧张性味觉反应明显；一些对四种基本刺激和食物的反应比对氯化铵的反应更好。在两个区域，仅相差几天的年龄，也观察到了抑制性反应。平均味觉反应在不同年龄增加或减少，这取决于味觉刺激的类型和记录区域。当沿横坐标按蔗糖、氯化钠、盐酸和奎宁的顺序将味觉反应与四种基本味觉刺激作图时，一些神经元呈现双峰反应曲线。这表明单个皮质神经元处传入纤维的汇聚和相互抑制。在两个区域，具有双峰反应曲线的神经元比例在25 - 35天龄时增加。25 - 35天龄大鼠的神经元主要对氯化铵或氯化钠敏感，或者对食物或蔗糖敏感。其他年龄大鼠在断奶前和成年阶段的神经元倾向于对这两种刺激都有反应。我们的观察结果表明，大鼠大脑中的皮质味觉神经元是随着味觉感受器和神经网络的成熟而发育的。
