Mohammadi Rabie, Jahanshahi Mehrdad, Jameie Seyed Behnamedin
Department of Anatomy, Neuroscience Research Center, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran.
Department of Anatomy, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Basic Clin Neurosci. 2016 Jul;7(3):249-58. doi: 10.15412/J.BCN.03070310.
A close interaction exists between the brain opioid and serotonin (5-HT) neurotransmitter systems. Brain neurotransmitter 5-HT plays an important role in the regulation of reward-related processing. However, a few studies have investigated the potential role of 5-HT2A receptors in this behavior. Therefore, the aim of the present study was to assess the influence of morphine and Conditioned Place Preference (CPP) on the density of 5-HT2A receptor in neurons of rat hippocampal formation.
Morphine (10 mg/kg, IP) was injected in male Wistar rats for 7 consecutive days (intervention group), but control rats received just normal saline (1 mL/kg, IP). We used a hotplate test of analgesia to assess induction of tolerance to analgesic effects of morphine on days 1 and 8 of injections. Later, two groups of rats were sacrificed one day after 7 days of injections, their whole brains removed, and the striatum and PFC immediately dissected. Then, the NR1 gene expression was examined with a semi-quantitative RT-PCR method.
Our data showed that the maximum response was obtained with 2.5 mg/kg of morphine. The density of 5-HT2A receptor in different areas of the hippocampus increased significantly at sham-morphine and CPP groups (P<0.05). On the other hand, the CPP groups had more 5-HT2A receptors than sham-morphine groups and also the sham-morphine groups had more 5-HT2A receptors than the control groups.
We concluded that the phenomenon of conditioned place preference induced by morphine can cause a significant increase in the number of serotonin 5-HT2A receptors in neurons of all areas of hippocampus.
大脑阿片类物质与血清素（5-羟色胺，5-HT）神经递质系统之间存在密切的相互作用。大脑神经递质5-HT在奖赏相关加工过程的调节中发挥重要作用。然而，仅有少数研究探讨了5-HT2A受体在这种行为中的潜在作用。因此，本研究的目的是评估吗啡和条件性位置偏爱（CPP）对大鼠海马结构神经元中5-HT2A受体密度的影响。
对雄性Wistar大鼠连续7天腹腔注射吗啡（10 mg/kg，干预组），而对照组大鼠仅接受生理盐水（1 mL/kg，腹腔注射）。我们在注射的第1天和第8天使用热板镇痛试验来评估对吗啡镇痛作用的耐受性诱导情况。之后，在注射7天后的第1天处死两组大鼠，取出全脑，立即解剖纹状体和前额叶皮质。然后，采用半定量逆转录聚合酶链反应（RT-PCR）方法检测NR1基因表达。
我们的数据显示，2.5 mg/kg的吗啡可获得最大反应。在假吗啡组和CPP组中，海马不同区域的5-HT2A受体密度显著增加（P<0.05）。另一方面，CPP组的5-HT2A受体比假吗啡组更多，且假吗啡组的5-HT2A受体也比对照组更多。
我们得出结论，吗啡诱导的条件性位置偏爱现象可导致海马所有区域神经元中血清素5-HT2A受体数量显著增加。
