Mohr Daniela, von Ameln-Mayerhofer Andreas, Fendt Markus
Animal Physiology, University of Tübingen, Tübingen, Germany.
Behav Brain Res. 2009 Aug 24;202(1):58-63. doi: 10.1016/j.bbr.2009.03.014. Epub 2009 Mar 21.
The prefrontal cortex and the nucleus accumbens are two brain sites which are known to be involved in the modulation of the acoustic startle response. In particular, the release of monoaminergic transmitters within these brain sites plays an important role in prepulse inhibition of the startle response which serves as an operational measure of sensorimotor gating. Like for dopamine, it is well established that serotonin transmission plays an important role in prepulse inhibition. However, there are only few studies investigating the effects of local manipulation of serotonin transmission on prepulse inhibition. The aim of the present study was to test whether prepulse inhibition or the startle response itself was affected by serotonergic depletion of either the prefrontal cortex or the nucleus accumbens. Serotonergic depletion was induced by local injections of 5,7-dihydroxytryptamine and verified by ex vivo analysis of transmitter levels by high pressure liquid chromatography. In our behavioural tests, we found that 5,7-dihydroxytryptamine into the prefrontal cortex decreased prepulse inhibition, whereas injections into the nucleus accumbens facilitated prepulse inhibition. The time course of these behavioural effects, as well as the transmitter level changes within the different brain sites was very different. Most interestingly, 5,7-dihydroxytryptamine injections into the nucleus accumbens affect serotonin and dopamine levels in both, nucleus accumbens and prefrontal cortex. Taken together, the present study supports an important role of serotonin in the modulation of prepulse inhibition and baseline startle magnitude. However, the observed changes cannot be attributed to a specific brain site since our data clearly show that local 5,7-dihydroxytryptamine injections also affect transmitter levels in brain sites away from the injection site.
前额叶皮质和伏隔核是已知参与调节听觉惊吓反应的两个脑区。特别是，这些脑区内单胺能递质的释放，在惊吓反应的前脉冲抑制中起着重要作用，而惊吓反应的前脉冲抑制是感觉运动门控的一项操作指标。与多巴胺一样，血清素传递在前脉冲抑制中起重要作用已得到充分证实。然而，仅有少数研究调查了血清素传递的局部操纵对前脉冲抑制的影响。本研究的目的是测试前额叶皮质或伏隔核的血清素耗竭是否会影响前脉冲抑制或惊吓反应本身。通过局部注射5,7 - 二羟基色胺诱导血清素耗竭，并通过高压液相色谱对递质水平进行离体分析来验证。在我们的行为测试中，我们发现向前额叶皮质注射5,7 - 二羟基色胺会降低前脉冲抑制，而向伏隔核注射则会促进前脉冲抑制。这些行为效应的时间进程以及不同脑区内递质水平的变化差异很大。最有趣的是，向伏隔核注射5,7 - 二羟基色胺会影响伏隔核和前额叶皮质中的血清素和多巴胺水平。综上所述，本研究支持血清素在前脉冲抑制和基线惊吓幅度调节中起重要作用。然而，观察到的变化不能归因于特定的脑区，因为我们的数据清楚地表明，局部注射5,7 - 二羟基色胺也会影响注射部位以外脑区的递质水平。
