Grabauskas G, Bradley R M
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
J Neurophysiol. 2001 May;85(5):2203-12. doi: 10.1152/jn.2001.85.5.2203.
To explore the postnatal development of inhibitory synaptic activity in the rostral (gustatory) nucleus of the solitary tract (rNST), whole cell and gramicidin perforated patch-clamp recordings were made in five age groups of rats [postnatal day 0-7 (P0-7), P8-14, P15-21, P22-30, and P >55]. The passive membrane properties of the developing rNST neurons as well as the electrophysiological and pharmacological characteristics of single and tetanic stimulus-evoked inhibitory postsynaptic potentials (IPSPs) were studied in brain slices under glutamate receptor blockade. During the first postnatal weeks, significant changes in resting membrane potential, spontaneous activity, input resistance, and neuron membrane time constant of the rNST neurons occurred. Although all the IPSPs recorded were hyperpolarizing, the rise and decay time constants of the single stimulus shock-evoked IPSPs decreased, and the inhibition response-concentration function to the gamma-aminobutyric acid (GABA) receptor antagonist bicuculline methiodide (BMI) shifted to the left during development. In P0-7 and P8-14, but not in older animals, the IPSPs had a BMI-insensitive component that was sensitive to block by picrotoxin, suggesting a transient expression of GABA(C) receptors. Tetanic stimulation resulted in both short- and long-term changes of inhibitory synaptic transmission in the rNST. For P0-7 and P8-14 animals tetanic stimulation resulted in a sustained hyperpolarization that was maintained for some time after termination of the tetanic stimulation. In contrast, tetanic stimulation of neurons in P15-21 and older animals resulted in hyperpolarization that was not sustained but decayed back to a more positive level with an exponential time course. Tetanic stimulation resulted in potentiation of single stimulus shock-evoked IPSPs in ~50% of neurons in all age groups. These developmental changes in inhibitory synaptic transmission in the rNST may play an important role in shaping synaptic activity in early development of the rat gustatory system during a time of maturation of taste preferences and aversions.
为了探究孤束吻侧（味觉）核（rNST）中抑制性突触活动的产后发育情况，对五个年龄组的大鼠[出生后第0 - 7天（P0 - 7）、P8 - 14、P15 - 21、P22 - 30以及P>55]进行了全细胞和短杆菌肽穿孔膜片钳记录。在谷氨酸受体阻断的情况下，研究了发育中的rNST神经元的被动膜特性以及单次和强直刺激诱发的抑制性突触后电位（IPSPs）的电生理和药理学特征。在出生后的头几周内，rNST神经元的静息膜电位、自发活动、输入电阻和神经元膜时间常数发生了显著变化。尽管记录到的所有IPSPs都是超极化的，但单次刺激诱发的IPSPs的上升和衰减时间常数缩短，并且在发育过程中，对γ-氨基丁酸（GABA）受体拮抗剂甲基荷包牡丹碱（BMI）的抑制反应 - 浓度函数向左移动。在P0 - 7和P8 - 14组中，但在年龄较大的动物中未观察到，IPSPs具有对BMI不敏感但对印防己毒素敏感的成分，提示GABA(C)受体的短暂表达。强直刺激导致rNST中抑制性突触传递的短期和长期变化。对于P0 - 7和P8 - 14组的动物，强直刺激导致持续超极化，在强直刺激终止后仍维持一段时间。相反，对P15 - 21组及年龄更大动物的神经元进行强直刺激导致超极化，但不持续，而是以指数时间进程衰减回到更正的水平。强直刺激导致所有年龄组中约50%的神经元单次刺激诱发的IPSPs增强。rNST中抑制性突触传递的这些发育变化可能在大鼠味觉系统早期发育过程中味觉偏好和厌恶成熟的时期塑造突触活动方面发挥重要作用。
