Bonsi Paola, Florio Tiziana, Capozzo Annamaria, Pisani Antonio, Calabresi Paolo, Siracusano Alberto, Scarnati Eugenio
Fondazione Santa Lucia IRCCS, Rome and Department of Neuroscience, Neurological Clinic, University 'Tor Vergata', Rome, Italy.
Eur J Neurosci. 2003 Jan;17(1):174-8. doi: 10.1046/j.1460-9568.2003.02410.x.
Cholinergic striatal interneurons play a crucial role in cognitive aspects of context-dependent motor behaviours. They are considered to correspond to the tonically active neurons (TANs) of the primate striatum, which phasically decrease their discharge at the presentation of reward-related sensory stimuli. The origin of this response is still poorly understood. Therefore, in the present paper, we have investigated whether synaptic changes establish in cholinergic interneurons from young rats that have learned a rewarded, externally cued sensorimotor task. Corticostriatal slices were prepared from both control and trained rats. No significant change in intrinsic membrane properties and evoked synaptic activity was observed in cholinergic interneurons, nor the responsiveness to exogenously applied dopaminergic and glutamatergic agonists was modified. Conversely, an increased occurrence of spontaneous bicuculline-sensitive depolarizing postsynaptic potentials (sDPSP) was recorded. The frequency of the GABAA-mediated sDPSP was increased in comparison to not-conditioned rats. Overall, these results suggest that after learning a rewarded sensorimotor paradigm an increased GABA influence develops on cholinergic interneurons. The origin of this effect might be searched in collaterals of GABAergic output spiny neurons as well as in GABAergic striatal interneurons impinging onto cholinergic interneurons. This intrastriatal mechanism might be involved in the phasic suppression of discharge of TANs at the presentation of reward-related sensory stimuli.
胆碱能纹状体中间神经元在依赖情境的运动行为的认知方面起着关键作用。它们被认为与灵长类动物纹状体的紧张性活动神经元（TANs）相对应，这些神经元在呈现与奖励相关的感觉刺激时会阶段性地减少放电。这种反应的起源仍知之甚少。因此，在本文中，我们研究了在学习了一项有奖励的、外部提示的感觉运动任务的幼鼠的胆碱能中间神经元中是否会发生突触变化。从对照大鼠和训练大鼠制备了皮质纹状体切片。在胆碱能中间神经元中未观察到内在膜特性和诱发突触活动的显著变化，对外源性应用的多巴胺能和谷氨酸能激动剂的反应性也未改变。相反，记录到自发的荷包牡丹碱敏感的去极化突触后电位（sDPSP）的发生率增加。与未训练的大鼠相比，GABAA介导的sDPSP的频率增加。总体而言，这些结果表明，在学习了有奖励的感觉运动范式后，胆碱能中间神经元上的GABA影响增强。这种效应的起源可能在于GABA能输出棘状神经元的侧支以及投射到胆碱能中间神经元上的GABA能纹状体中间神经元。这种纹状体内机制可能参与了在呈现与奖励相关的感觉刺激时TANs放电的阶段性抑制。
