Swithers S E, Westneat M W, Hall W G
Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Physiol Behav. 1998 Jan;63(2):197-203. doi: 10.1016/s0031-9384(97)00421-6.
Rat pups show decreases in mouthing activity in response to a series of repeated oral infusions of a diet. This decrease in mouthing activity has been termed "oral habituation" and these changes have been readily recorded with simple behavioral observations. Oral habituation appears to be a component of satiety in young rats. In the present study, to more specifically characterize changes in motor response topography during habituation in muscle groups used for mastication, mouthing activity was recorded by implanting fine wire electromyographic electrodes in the superficial masseter, anterior digastric, sternohyoideus, and genioglossus muscles of 12-day-old rat pups. During testing, pups received a series of brief oral infusions of a 10% sucrose diet delivered through an oral cannula. The results demonstrated that mouthing activity as observed and scored behaviorally was highly correlated with mouthing behavior recorded by EMG, with oral habituation distinctly emerging in both measures. In addition, the pattern of motor activity in the four masticatory muscles changed during the course of oral habituation. Within the minute following a single infusion, the cycle frequency, duration of activity, and relative onset time of activity in the four muscles changed. In addition, across the course of habituation, both cycle frequency and relative onset times of muscle activity changed. These results demonstrate the general reliability of behavioral observations of masticatory motor activity in young rats and provide further information on how the pattern of activity of muscles involved in the mouthing motor pattern is altered during the course of oral habituation.
幼鼠在接受一系列重复的口服喂食后，其口部活动会减少。这种口部活动的减少被称为“口腔习惯化”，并且这些变化可以通过简单的行为观察轻易记录下来。口腔习惯化似乎是幼鼠饱腹感的一个组成部分。在本研究中，为了更具体地描述咀嚼所用肌肉群在习惯化过程中运动反应地形图的变化，通过在12日龄幼鼠的浅层咬肌、前腹直肌、胸骨舌骨肌和颏舌肌中植入细钢丝肌电图电极来记录口部活动。在测试过程中，幼鼠通过口腔插管接受一系列短暂的10%蔗糖饮食口服输注。结果表明，行为观察到并评分的口部活动与肌电图记录的口部行为高度相关，两种测量方法中均明显出现了口腔习惯化。此外，在口腔习惯化过程中，四块咀嚼肌的运动活动模式发生了变化。在单次输注后的一分钟内，四块肌肉的周期频率、活动持续时间和活动相对起始时间发生了变化。此外，在习惯化过程中，肌肉活动的周期频率和相对起始时间均发生了变化。这些结果证明了幼鼠咀嚼运动活动行为观察的总体可靠性，并提供了关于参与口部运动模式的肌肉活动模式在口腔习惯化过程中如何改变的进一步信息。
