Sharf Ruth, Ranaldi Robert
Department of Psychology, Queens College, CUNY, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
Psychopharmacology (Berl). 2006 Jan;184(1):87-94. doi: 10.1007/s00213-005-0235-9. Epub 2005 Nov 24.
Stimulation of ventral tegmental area (VTA) muscarinic acetylcholine receptors (mAChRs) is implicated in feeding.
To investigate the effects of mAChR blockade in the VTA on food-related learning.
In experiment 1, rats (N=12) were placed in chambers containing food and received microinjections of 0 or 5 microg/0.5 microl scopolamine prior to the first four feeding sessions and the alternate dose prior to the tenth feeding session. In experiment 2 (N=9), the effects of daily microinjections of scopolamine on lever pressing under a progressive ratio schedule of food reinforcement were tested. In experiment 3 (N=34), the effects of daily microinjections of scopolamine on lever pressing maintained by conditioned reward were investigated.
In experiment 1, all rats demonstrated low consumption during session 1. However, pellet consumption for rats initially pretreated with the 0-microg dose rose to and stayed at maximal levels for the remaining sessions, even when pretreated with the 5-microg dose during the tenth session. Pellet consumption for rats initially pretreated with the 5-microg dose remained low, even for the first two sessions following the cessation of scopolamine pretreatment, and gradually rose to maximal levels by the eighth session. In experiment 2, scopolamine significantly decreased break points. In experiment 3, scopolamine failed to significantly decrease responding specifically on the lever producing the conditioned reward.
Altogether, these data suggest that VTA mAChR stimulation is involved in feeding and food-related learning but may not be involved in responding maintained by conditioned reward.
腹侧被盖区（VTA）毒蕈碱型乙酰胆碱受体（mAChRs）的刺激与进食有关。
研究VTA中mAChR阻断对食物相关学习的影响。
在实验1中，将大鼠（N = 12）置于装有食物的实验箱中，在前四次进食前接受0或5微克/0.5微升东莨菪碱的微量注射，在第十次进食前接受交替剂量注射。在实验2（N = 9）中，测试了每日微量注射东莨菪碱对食物强化渐进比率程序下杠杆按压的影响。在实验3（N = 34）中，研究了每日微量注射东莨菪碱对条件性奖励维持的杠杆按压的影响。
在实验1中，所有大鼠在第1次进食时均表现出低消耗量。然而，最初用0微克剂量预处理的大鼠的颗粒消耗量在其余进食时上升并保持在最高水平，即使在第十次进食时用5微克剂量预处理也是如此。最初用5微克剂量预处理的大鼠的颗粒消耗量仍然很低，即使在东莨菪碱预处理停止后的前两次进食时也是如此，并在第八次进食时逐渐上升到最高水平。在实验2中，东莨菪碱显著降低了断点。在实验3中，东莨菪碱未能显著降低在产生条件性奖励的杠杆上的特异性反应。
总之，这些数据表明VTA mAChR刺激参与进食和食物相关学习，但可能不参与条件性奖励维持的反应。
