Young K A, Hicks P B, Randall P K, Wilcox R E
Department of Psychiatry and Behavorial Science, Texas A&M University Health Science Center, Scott & White Clinic, Temple, USA.
J Neural Transm Gen Sect. 1994;98(2):119-32. doi: 10.1007/BF01277015.
To study sensorimotor correlates of dopamine (DA) and gamma-amino butyric acid (GABA) neurotransmission in the thalamus, we microinjected the DA agonist apomorphine (APO), the GABA agonist muscimol and vehicle into the mediodorsal thalamic nucleus (MdT) of rats and monitored catalepsy, sensorimotor asymmetries and the acoustic startle response. Unilateral MdT muscimol microinjections (50 ng) produced a lateralization of the removal of adhesive disks placed simultaneously on both forelegs in a tactile extinction task, but did not measurably influence any aspects of startle behavior. The sensorimotor asymmetry consisted of perferential orientation to the adhesive disk on the side ipsilateral to the microinjection. Vehicle and APO microinjections produced no significant behavioral results. In a follow-up study, unilateral MdT muscimol microinjections significantly depressed medial prefrontal cortical metabolism (measured by 2-fluorodeoxyglucose uptake) by 24%, but did not affect nucleus accumbens metabolic activity. Together, these findings are consistent with the concept that GABA-mediated inhibition of thalamocortical neurons in the MdT influences tactile extinction behavior, most likely by selectively suppressing excitatory input to the frontal cortex. The sensorimotor asymmetry observed in the present study resembles attentional and spatial memory deficits associated with frontal cortical lesions, and in conjunction with the 2-fluorodeoxyglucose results, suggests that elevated GABA neurotransmission in the thalamus may be involved in attentional and functional metabolic deficits in humans.
为研究丘脑多巴胺（DA）和γ-氨基丁酸（GABA）神经传递的感觉运动相关性，我们将DA激动剂阿扑吗啡（APO）、GABA激动剂蝇蕈醇和溶剂微量注射到大鼠的背内侧丘脑核（MdT）中，并监测僵住症、感觉运动不对称性和听觉惊吓反应。单侧MdT微量注射蝇蕈醇（50纳克）在触觉消退任务中导致同时放置在两条前腿上的粘性圆盘去除出现侧向化，但对惊吓行为的任何方面均无明显影响。感觉运动不对称表现为对微量注射同侧粘性圆盘的优先朝向。注射溶剂和APO未产生显著的行为结果。在后续研究中，单侧MdT微量注射蝇蕈醇显著降低内侧前额叶皮质代谢（通过2-氟脱氧葡萄糖摄取测量）24%，但不影响伏隔核的代谢活性。总之，这些发现与以下概念一致，即GABA介导的对MdT中丘脑皮质神经元的抑制影响触觉消退行为，最可能是通过选择性抑制对额叶皮质的兴奋性输入。本研究中观察到的感觉运动不对称类似于与额叶皮质损伤相关的注意力和空间记忆缺陷，结合2-氟脱氧葡萄糖的结果，表明丘脑中GABA神经传递增强可能与人类的注意力和功能性代谢缺陷有关。
