Ikemoto Satoshi, Qin Mei, Liu Zhong-Hua
Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland 21224, USA.
J Neurosci. 2006 Jan 18;26(3):723-30. doi: 10.1523/JNEUROSCI.4542-05.2006.
Nicotine is thought to be the key substance responsible for tobacco-smoking habits and appears to trigger reinforcement via the ventral tegmental area (VTA). Recently, multiple anatomical substrates for drug reinforcement have been identified in the vicinity of the ventral midbrain. In addition to the posterior portion of the VTA, the central linear nucleus raphé and the supramammillary nucleus of the posterior hypothalamus mediate drug reinforcement. Using intracranial self-administration procedures, we examined whether these regions mediate the reinforcing effects of nicotine. Rats learned to lever press for self-administration of nicotine into the posterior VTA, central linear nucleus, and supramammillary nucleus, suggesting a reinforcing action of nicotine in these regions. The rats did not self-administer nicotine into surrounding regions including the anterior VTA, substantia nigra, the region just dorsal to the posterior VTA, interpeduncular nucleus, or medial mammillary nucleus. The reinforcing effects of nicotine into the three brain regions were further confirmed by a two-lever discrimination procedure, in which rats learned to selectively respond between active and inactive levers. The reinforcing effects of nicotine administration into the posterior VTA, central linear nucleus, and supramammillary nucleus were blocked by coadministration of the nicotine receptor antagonist mecamylamine. The reinforcing effects of nicotine into the posterior VTA or central linear nucleus were attenuated by coadministration of the D2 receptor agonist quinpirole. These findings demonstrate that nicotine reinforcement involves multiple regions both inside and outside the VTA.
尼古丁被认为是导致吸烟习惯的关键物质,并且似乎通过腹侧被盖区(VTA)触发强化作用。最近,在腹侧中脑附近发现了多种药物强化的解剖学底物。除了VTA的后部,中缝中央线性核和下丘脑后部的乳头体上核也介导药物强化。我们使用颅内自我给药程序,研究了这些区域是否介导尼古丁的强化作用。大鼠学会了按压杠杆以将尼古丁自我注射到VTA后部、中央线性核和乳头体上核,这表明尼古丁在这些区域具有强化作用。大鼠不会将尼古丁自我注射到周围区域,包括VTA前部、黑质、VTA后部背侧的区域、脚间核或内侧乳头体核。通过双杠杆辨别程序进一步证实了尼古丁在这三个脑区的强化作用,在该程序中,大鼠学会了在活动杠杆和非活动杠杆之间进行选择性反应。同时给予尼古丁受体拮抗剂美加明可阻断将尼古丁注射到VTA后部、中央线性核和乳头体上核所产生的强化作用。同时给予D2受体激动剂喹吡罗可减弱将尼古丁注射到VTA后部或中央线性核所产生的强化作用。这些发现表明,尼古丁强化作用涉及VTA内外的多个区域。