Department of Animal Physiology, University of Gdańsk, Kładki 24, 80-822 Gdańsk, Poland.
Brain Res Bull. 2010 Nov 20;83(6):310-20. doi: 10.1016/j.brainresbull.2010.09.006. Epub 2010 Sep 22.
Previously we indicated that the ventral tegmental area (VTA) may belong to the system regulating hippocampal theta rhythm. In the present study, we aimed at assessing the role of the GABAergic system of the VTA in regulation of hippocampal electric activity. Male Wistar rats received unilateral intra-VTA microinjection of either bicuculline (50ng/0.5μl, n=9), muscimol (100ng/0.5μl, n=10) or phaclofen (500ng/0.5μl, n=9). 1-min tail pinch stimulations were applied at 10-min intervals to evoke theta rhythm episodes in hippocampus. We analysed peak power (P(max)) and corresponding frequency (F(max)) of EEG signal at delta and theta bands. Bicuculline induced theta rhythm in both hippocampi with 0 latency, continuous for ca. 33min. Phaclofen also induced theta but in this group it appeared with latency (17.45±3.16min on average), lasted for ca. 33.6min and during this time was interrupted by periods of irregular activity of variable length. Tail pinch was not applied in these groups. Muscimol induced an opposite effect: depression of theta P(max) with simultaneous increase in delta P(max) and a decrease in F(max) delta during episodes of tail pinch-evoked theta. This effect had variable latency and no return to the control EEG could be observed. We propose that GABA activity in the VTA is of tonic character, so that abolition of this mechanism produces immediate effect, i.e. theta induction (strong by GABA(A) and weak by GABA(B) receptors blockade), whereas enhancing the already present GABAergic inhibition causes delayed, prolonged changes expressed as gradual loss of theta synchronisation.
先前我们指出，腹侧被盖区（VTA）可能属于调节海马θ节律的系统。在本研究中，我们旨在评估VTA的GABA能系统在调节海马电活动中的作用。雄性Wistar大鼠接受VTA单侧微量注射荷包牡丹碱（50ng/0.5μl，n = 9）、蝇蕈醇（100ng/0.5μl，n = 10）或巴氯芬（500ng/0.5μl，n = 9）。每隔10分钟进行1分钟的夹尾刺激，以诱发海马中的θ节律发作。我们分析了脑电图信号在δ和θ频段的峰值功率（P(max)）和相应频率（F(max)）。荷包牡丹碱在双侧海马中均诱发了θ节律，潜伏期为0，持续约33分钟。巴氯芬也诱发了θ节律，但在该组中出现了潜伏期（平均为17.45±3.16分钟），持续约33.6分钟，在此期间被不同长度的不规则活动期打断。这些组未进行夹尾刺激。蝇蕈醇产生了相反的效果：在夹尾诱发θ节律的发作期间，θ P(max)降低，同时δ P(max)增加，δ频段的F(max)降低。这种效应潜伏期不定，未观察到恢复到对照脑电图的情况。我们提出，VTA中的GABA活性具有紧张性特征，因此消除该机制会立即产生效应，即诱发θ节律（通过GABA(A)受体阻断作用强烈，通过GABA(B)受体阻断作用较弱），而增强已存在的GABA能抑制作用会导致延迟、持久的变化，表现为θ同步性逐渐丧失。
