Soltesz I, Lightowler S, Leresche N, Crunelli V
Department of Pharmacology, St. George's Hospital Medical School, London, U.K.
Brain Res. 1989 Feb 6;479(1):49-55. doi: 10.1016/0006-8993(89)91334-6.
The inhibitory postsynaptic potentials (IPSPs) evoked in neurons of the rat ventral geniculate nucleus (vLGN) by electrical stimulation of the optic tract and the action of GABA and baclofen on the same cells were studied using intracellular recording technique in an in vitro slice preparation. A short latency short duration IPSP always followed the monosynaptic excitatory postsynaptic potential (EPSP). This IPSP reversed in polarity at about -65 mV and was reversibly blocked by bicuculline (50 microM) thus indicating that it represents a GABAA receptor-mediated IPSP. No long-lasting IPSP was evoked in vLGN cells by stimulation of the optic tract, while in the same slice, long-lasting GABAB IPSPs were routinely recorded in the dorsal lateral geniculate nucleus. GABA applied by ionophoresis evoked a hyperpolarization that had a reversal potential close to -70 mV and was antagonized by bicuculline. Baclofen hyperpolarized vLGN neurons and its action was reversibly blocked by the selective GABAB antagonist phaclofen (1 mM). In the presence of bicuculline GABA also produced a hyperpolarization that had properties similar to that evoked by baclofen. These results indicate that, although functional GABAA and GABAB receptors are present on vLGN neurons, stimulation of the optic tract evokes only GABAA but not GABAB mediated IPSPs. The lack of long-lasting GABAB IPSPs could explain the absence of long-lasting inhibition observed in vLGN neurons in vivo following stimulation of the optic tract.
采用细胞内记录技术，在体外脑片制备中研究了电刺激大鼠视束在腹侧膝状核（vLGN）神经元中诱发的抑制性突触后电位（IPSP），以及GABA和巴氯芬对这些细胞的作用。一个潜伏期短、时程短的IPSP总是跟随单突触兴奋性突触后电位（EPSP）出现。这个IPSP在约-65 mV时极性反转，并被荷包牡丹碱（50 μM）可逆性阻断，因此表明它代表一种GABAA受体介导的IPSP。对视束进行刺激时，vLGN细胞中未诱发出长时程IPSP，而在同一片脑片中，背外侧膝状核中则常规记录到长时程GABAB IPSP。通过离子导入施加的GABA诱发了一种超极化，其反转电位接近-70 mV，并被荷包牡丹碱拮抗。巴氯芬使vLGN神经元超极化，其作用被选择性GABAB拮抗剂巴氯芬（1 mM）可逆性阻断。在存在荷包牡丹碱的情况下，GABA也产生了一种与巴氯芬诱发的超极化性质相似的超极化。这些结果表明，虽然vLGN神经元上存在功能性GABAA和GABAB受体，但对视束的刺激仅诱发GABAA介导而非GABAB介导的IPSP。缺乏长时程GABAB IPSP可以解释在体内对视束进行刺激后vLGN神经元中未观察到长时程抑制的现象。
