γ-氨基丁酸对离体大鼠延髓头端腹外侧区神经元单位放电的抑制作用(英文)

INHIBITORY EFFECT OF GABA ON FIRING ACTIVITY OF ROSTRAL VENTROLATERAL MEDULLARY NEURONS OF RAT IN VITRO

在73张脑片上观察了γ-氨基丁酸（GABA）对106个延髓头端腹外侧区（RVLM）神经元单位放电的影响。外源性的GABA（0．1－3．0mmol／L）抑制了106神经元中的84个神经元的电活动，这些抑制效应呈剂量-反应关系。GABA的抑制效应大部分可被GABAA受体选择性拮抗剂荷苞牡丹碱甲基碘化物（BMI）和Cl-通道阻断剂印防己毒素（PTX）所阻断，而单独灌流BMI和PTX对RVLM神经元主要起兴奋作用。在41个对GABA有抑制效应的RVLM神经元上，GABAB受体选择性激动剂苯氯丁氨酸（0．1－3．0μmnol／L）抑制了其中33个神经元的单位放电，也呈剂量-反应关系。GABAB受体选择性拮抗剂CGP35348（n＝13）可阻断苯氯丁氨酸的抑制效应（n＝21），而单独灌流CGP35348对RVLM神经元主要起兴奋作用。上述结果提示：GABA对RVLM神经元的抑制效应，不仅可以通过GABAA受体，而且可以通过GABAB受体起作用；内源性的GABA参与了紧张性的抑制作用。

Extracellular single-unit discharges were obtained from 106 spontaneously active neurons inthe region of the rostral ventrolateral medulla (RVLM) by glass microelectrode from 73 brain slices of SpragueDawley rats. Exogenous γ-aminobutyric acid (GABA, 0. 1 ~3.0 mmol/L) inhibited the electrical activity of84 out of 106 RVLM neurons dose-dependently. The inhibitory effect of GABA could be blocked by GABAAreceptor antagonist bicuculline bicuculline methiodide (BMI) and Cl- channel blocker picrotokin (PTX). When perfusedwith BMI or PTX alone, the firing rates of most of the RVLM neurons were significantly increased. In 41neurons responding to GABA, baclofen (0. 1 ~ 3.0 μmol/L), a GABAB receptor selective agonist, inhibitedthe discharges of 33 of the neurons dose-dependently. GABAB receptor antagonist CGP35348 (n = 13) blockedthe inhibition due to baclofen (n = 21 ). After perfused with CGP35348 alone, the firing rates of most of theRVLM neurons were significantly increased. Taken together, the inhibition of GABA on RVLM neurons ismediated through either CABAA or GABAB receptors and some intrinsic GABA neurons exert tonic inhibitionactivity.