Malkusz Danielle C, Bernal Sonia Y, Banakos Theodore, Malkusz Gina, Mohamed Andrew, Vongwattanakit Tracy, Bodnar Richard J
Behavioral and Cognitive Neuroscience Cluster, Psychology Doctoral Program, The Graduate Center and Department of Psychology, New York, NY, USA.
Queens College, City University of New York, New York, NY, USA.
Neurosci Lett. 2014 Apr 3;564:94-8. doi: 10.1016/j.neulet.2014.02.020. Epub 2014 Feb 20.
In prior studies, systemic opioid receptor antagonism with naltrexone (NTX) failed to block flavor preference conditioning by the sweet taste or post-oral actions of sugar despite reducing overall flavored saccharin intake. Further, NTX microinjections into the nucleus accumbens (NAc) shell or core failed to alter the expression of preferences conditioned by the sweet taste or post-oral actions of sugars. In contrast, fructose-conditioned flavor preferences (CFP) were reduced or eliminated by systemic or intracerebral administration of dopamine (DA) D1 or D2 antagonists in the NAc, medial prefrontal cortex (mPFC), amygdala (AMY) or lateral hypothalamus (LH). The present study examined whether NTX microinjections into the mPFC, AMY or LH would alter expression of fructose-CFP and total flavored saccharin intake. Food-restricted rats with bilateral cannulae aimed at the mPFC, AMY or LH were trained to drink a fructose (8%)+saccharin (0.2%) solution mixed with one flavor (CS+, e.g., cherry) and a 0.2% saccharin solution mixed with another flavor (CS-, e.g., grape) during 10 one-bottle sessions. Two-bottle tests with the cherry and grape flavors in 0.2% saccharin solutions occurred 10min following total bilateral NTX doses of 0, 1, 25 and 50μg administered into the mPFC, AMY or LH. Rats preferred the CS+ over CS- flavor following vehicle and all NTX doses administered into either the mPFC or LH. CS+ intake was significantly greater than CS- intake following vehicle and the low NTX dose in the AMY; however, at the 25 and 50μg AMY NTX doses, CS+ intakes did not significantly exceed CS- intakes. Total flavored saccharin intake was significantly reduced by all three LH NTX doses (20-35%), by the 25 (14%) and 50 (22%)μg AMY NTX doses, but not by mPFC NTX. Thus, opioid antagonism in the AMY, but not the mPFC or LH attenuated, but did not block the expression of fructose-CFP, and LH and AMY, but not mPFC, NTX significantly reduced total saccharin intake. Therefore, whereas opioid antagonism in the LH and AMY reduces sweet intake, they appear less effective in altering fructose-CFP.
在先前的研究中，尽管纳曲酮（NTX）降低了总的加味糖精摄入量，但用其进行全身阿片受体拮抗作用未能通过甜味或糖的口腔后作用来阻断味觉偏好条件反射。此外，向伏隔核（NAc）壳部或核心微注射NTX未能改变由甜味或糖的口腔后作用所形成的偏好的表达。相比之下，在NAc、内侧前额叶皮质（mPFC）、杏仁核（AMY）或外侧下丘脑（LH）中，全身或脑内给予多巴胺（DA）D1或D2拮抗剂可降低或消除果糖条件性味觉偏好（CFP）。本研究考察了向mPFC、AMY或LH微注射NTX是否会改变果糖-CFP的表达以及总的加味糖精摄入量。将双侧套管分别对准mPFC、AMY或LH的食物受限大鼠，在10次单瓶实验中训练它们饮用一种与一种味道（条件刺激+，例如樱桃）混合的果糖（8%）+糖精（0.2%）溶液，以及一种与另一种味道（条件刺激-，例如葡萄）混合的0.2%糖精溶液。在向mPFC、AMY或LH双侧总共给予0、1、25和50μg NTX剂量10分钟后，用0.2%糖精溶液进行樱桃味和葡萄味的双瓶测试。在用溶剂处理以及向mPFC或LH给予所有NTX剂量后，大鼠对条件刺激+味道的偏好超过条件刺激-味道。在用溶剂处理以及在AMY给予低剂量NTX后，条件刺激+的摄入量显著大于条件刺激-的摄入量；然而，在AMY给予25和50μg NTX剂量时，条件刺激+的摄入量并未显著超过条件刺激-的摄入量。所有三个LH NTX剂量（20 - 35%）、25（14%）和50（22%）μg AMY NTX剂量均显著降低了总的加味糖精摄入量，但mPFC NTX未使其降低。因此，AMY中的阿片类拮抗剂减弱但未阻断果糖-CFP的表达，而mPFC中的阿片类拮抗剂则没有这种作用，并且LH和AMY而非mPFC中的NTX显著降低了总的糖精摄入量。所以，尽管LH和AMY中的阿片类拮抗剂减少了甜味摄入，但它们在改变果糖-CFP方面似乎效果较差。
