Mark G P, Scott T R, Chang F C, Grill H J
Department of Psychology, Princeton University, NJ 08544.
Brain Res. 1988 Mar 8;443(1-2):137-48. doi: 10.1016/0006-8993(88)91606-x.
The ingestive behavior of decerebrate rats has been studied for some time, yet little is known of its neural substrates. While taste fibers in rats proceed from hindbrain to thalamus and ventral forebrain, these regions return centrifugal fibers to the hindbrain by which lower-order taste activity may be influenced. We examined the functional characteristics of taste neurons in the nucleus tractus solitarii (NTS) of chronic decerebrate rats in which this reciprocal communication was disrupted and compared them with those of intact controls. Nine Wistar rats were decerebrated at the supracollicular level. After a minimum of one week recovery, they were immobilized with Flaxedil, anesthetized locally and prepared for recording. The responses of 50 taste cells were isolated bilaterally from the NTS of these animals, while the activity of 50 additional neurons was recorded from 12 intact rats under the same conditions. Taste stimuli included 7 Na-Li salts, 3 sugars, HCl and citric acids, quinine HCl and NaSaccharin. Mean spontaneous activity in decerebrates was 6.5 spikes/s, 36.0% lower than the level in intact animals. Mean evoked activity was reduced by 32.6%. Analyses of the effects of stimulus quality, intensity and time course of the responses all indicated that the decrease in activity was attributable to the inability of taste cells in decerebrate rats to respond to demands for high discharge rates. This deficit could be responsible for the failure of these animals to develop conditioned taste aversions. Neurons from decerebrate preparations did, however, retain the broad sensitivity across stimuli that characterized taste cells in intact preparations. It was also typical that most neuron response profiles from decerebrates could be grouped into 3 loose clusters with peak sensitivities to acid-salt, salt or sugar. An analysis of similarities among stimulus activity profiles indicated that Na-Li salts, sugars and an acid-quinine complex represented 3 groups of stimulus quality; in intact animals, the primary distinction was between sweet and non-sweet stimuli. Moreover, the response to sodium saccharin lost its bitter component in decerebrates. These findings were in general agreement with those derived from acute decerebrate rats.
对去大脑大鼠的摄食行为已经研究了一段时间，但对其神经基质却知之甚少。虽然大鼠的味觉纤维从后脑延伸至丘脑和腹侧前脑，但这些区域会向后脑返回离心纤维，通过这些纤维可能会影响低级味觉活动。我们研究了慢性去大脑大鼠孤束核（NTS）中味觉神经元的功能特性，在这些大鼠中这种相互通信被破坏，并将它们与完整对照组的神经元功能特性进行了比较。9只Wistar大鼠在中脑上丘水平进行了去大脑手术。经过至少一周的恢复后，用三碘季铵酚使其固定，局部麻醉并准备进行记录。从这些动物的双侧NTS中分离出50个味觉细胞的反应，同时在相同条件下从12只完整大鼠中记录另外50个神经元的活动。味觉刺激包括7种钠-锂盐、3种糖、盐酸和柠檬酸、盐酸奎宁和糖精钠。去大脑大鼠的平均自发活动为6.5个脉冲/秒，比完整动物的水平低36.0%。平均诱发活动降低了32.6%。对刺激质量、强度和反应时间进程的影响分析均表明活动的降低归因于去大脑大鼠的味觉细胞无法对高放电率的需求做出反应。这种缺陷可能是这些动物无法形成条件性味觉厌恶的原因。然而，来自去大脑制剂的神经元确实保留了完整制剂中味觉细胞所具有的对多种刺激的广泛敏感性。同样典型的是，大多数来自去大脑大鼠的神经元反应图谱可以分为3个松散的簇，对酸盐、盐或糖具有峰值敏感性。对刺激活动图谱之间相似性的分析表明，钠-锂盐、糖和酸-奎宁复合物代表3组刺激质量；在完整动物中，主要区别在于甜味和非甜味刺激之间。此外，在去大脑大鼠中，对糖精钠的反应失去了其苦味成分。这些发现与从急性去大脑大鼠中得出的结果总体一致。
