Learning behavior in rat offspring after in utero and lactational exposure to either TCDD or PCB126

研究并比较了子宫内和哺乳期暴露于2,3,7,8 -四氯二苯并对二恶英（TCDD）或3,3 ',4,4 '，5-五氯联苯（PCB 126）对后代学习行为的可能影响。在妊娠第15天给予妊娠长-埃文斯大鼠TCDD（50、200或800 ng/kg）或PCB126（500、2000或8000 ng/kg）。采用进度控制操作行为方法对11周龄雄性和雌性幼鼠的学习行为进行了为期30天的观察。采用固定比率（FR）和低比率差异强化（DRL）的反应率和多个FR20 drl2o（多FR20 drl2o）测试中DRL成分的奖励率三个指标来评价学习行为。在子宫内和哺乳期暴露于TCDD或PCB 126对雄性和雌性幼崽学习行为的毒性影响主要在FR学习部分观察到。然而，这两个成分中的任何一个对上述三个指标都没有影响。低剂量TCDD和PCB126组动物反应率下降，中剂量TCDD和PCB126组动物出现过动行为。就学习行为的习得而言，高剂量的多氯联苯126似乎与TCDD具有明显的毒性。TCDD和PCB 126在学习行为中的毒性可能彼此相似，目前PCB 126的毒性等效因子（TEF）为0.1可以被认为适合于该终点。

I studies and compared the possible effects of in utero and lactational exposure to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) or 3, 3', 4, 4', 5-pentachlorobiphenyl (PCB 126) on learning behaviour in offspring. Pregnant Long-Evans Hooded rats were administered either TCDD (50, 200 or 800 ng/kg) or PCB126 (500, 2000 or 8000 ng/kg) on gestational day 15. A procedure of schedule-controlled operant behavior was applied to examine learning behavior in the male and female offspring at 11 weeks of age for 30 days. Three indices, namely, response rates in a fixed ratio (FR) and in a differential reinforcement of low rates (DRL), and reward rate in DRL component in a multiple FR20 DRL2Os (mult-FR20 DRL20s) test sessions, were used for the evaluation of learning behavior. Toxic effects on learning behaviour in male and female pups following in utero and lactational exposure to TCDD or PCB 126 were observed mainly in the FR learning component. However, effects of either of the two components were observed for the above three indices. The response rates of animals in the low-dose TCDD and PCB126 groups decreased and those in medium-dose TCDD and PCB 126 groups appeared to induce hyperactive behavior. The high dose of PCB 126 appeared to have a distinct toxicity from that of TCDD in terms of the acquisition of learning behavior. Toxicities of TCDD and PCB 126 in learning behaviour might be similar to each other and the current toxic equivalency factor (TEF) of 0.1 for PCB 126 can be considered to be appropriate for this endpoint.