Dutia M B, Johnston A R, McQueen D S
Department of Physiology, Medical School, Edinburgh, UK.
Exp Brain Res. 1992;88(3):466-72. doi: 10.1007/BF00228176.
The spontaneous discharge of 48 medial vestibular nucleus (MVN) neurones was recorded extracellularly in horizontal slices of the rat brainstem in vitro. The mean tonic rate of discharge was 17.1 +/- 8.2 imp/s, similar to that observed by others in transverse (coronal) slices of the rat and guinea pig MVN. The tonic rate of discharge of individual MVN cells either increased or decreased after synaptic blockade in low Ca2+ media, suggesting that ongoing synaptic activity has an important influence on the spontaneous activity of MVN cells in vitro. However the persistence of tonic activity after synaptic blockade indicates that an intrinsic, pacemaker-like mechanism is involved in the generation of the tonic activity. GABA, muscimol, baclofen and 3-APA inhibited the tonic activity of all MVN cells tested. Bicuculline antagonised, and picrotoxin blocked, the inhibitory responses to muscimol, but the effects of GABA were only partially blocked in 50 microM picrotoxin. The effects of baclofen and 3-APA persisted in low Ca2+ media, and were antagonised by saclofen and phaclofen. Picrotoxin-resistant responses to GABA persisted in low Ca2+ media, and were also antagonised by saclofen. These results suggest that the inhibitory control of MVN neurones by GABA involves both the GABAA and GABAB subtypes of GABA receptor. GABAB receptors appear to be distributed both pre- and post-synaptically in the rat MVN. The possible significance of the intrinsic, tonic activity of MVN cells in normal vestibular function and in vestibular compensation, and the effects of GABA, are discussed.
在体外对大鼠脑干水平切片中的48个内侧前庭核（MVN）神经元的自发放电进行了细胞外记录。平均紧张性放电频率为17.1±8.2次/秒，与其他人在大鼠和豚鼠MVN的横向（冠状）切片中观察到的相似。在低钙培养基中进行突触阻断后，单个MVN细胞的紧张性放电频率要么增加要么降低，这表明持续的突触活动对体外MVN细胞的自发放电有重要影响。然而，突触阻断后紧张性活动的持续存在表明，一种内在的、类似起搏器的机制参与了紧张性活动的产生。GABA、蝇蕈醇、巴氯芬和3-氨基丙酸抑制了所有测试的MVN细胞的紧张性活动。荷包牡丹碱拮抗，印防己毒素阻断了对蝇蕈醇的抑制反应，但在50微摩尔印防己毒素中，GABA的作用仅被部分阻断。巴氯芬和3-氨基丙酸的作用在低钙培养基中持续存在，并被赛氯芬和苯环芬拮抗。对GABA的印防己毒素抗性反应在低钙培养基中持续存在，也被赛氯芬拮抗。这些结果表明，GABA对MVN神经元的抑制性控制涉及GABAA和GABAB两种GABA受体亚型。GABAB受体似乎在大鼠MVN的突触前和突触后均有分布。讨论了MVN细胞内在紧张性活动在正常前庭功能和前庭代偿中的可能意义以及GABA的作用。
