GABAB受体介导对新生大鼠逼尿肌条的场刺激诱导收缩的抑制作用。
GABAB receptor mediated inhibition of field stimulation induced contractions of detrusor muscle strips from newborn rats.
作者信息
Maggi C A, Santicioli P, Meli A
出版信息
J Auton Pharmacol. 1984 Mar;4(1):45-51. doi: 10.1111/j.1474-8673.1984.tb00432.x.
The effect of GABA on field stimulation (0.1 Hz) induced contractions have been examined on detrusor strips from adult and newborn rats. Field stimulation induced contractions were unaffected by hexamethonium (10(-5) M) but almost suppressed by tetrodotoxin (5 X 10(-7) M) in both age groups. Atropine (3 X 10(-6) M) produced a marked inhibition of twitches in detrusor strips from newborn rats but only a slight (10% or less) inhibition in strips from adult animals. Neither GABA (10(-4), homotaurine (10(-3) M) or (+/-)-baclofen (10(-4] affected twitches in detrusor strips from adults rats. On the other hand both GABA and (+/-)-baclofen inhibited, to about the same extent (55-60% inhibition) twitches in detrusor strips from newborn animals. Homotaurine had no significant effect. The effects of both GABA (10(-4) M) and (+/-)-baclofen (10(-4) M) on twitches in detrusor strips from newborn rats were reduced if the preparations were previously exposed to a low concentration of GABA (5 X 10(-6) M) thus indicating desensitization. The inhibitory effect of GABA on twitches in newborn rats were concentration dependent in the range of 10(-7) to 10(-4) M. The GABAA receptor antagonist picrotoxin (10(-4) M) had no effect on the GABA concentration response curve whereas the GABAB receptor antagonist, homotaurine, produced an antagonism of the competitive type. The calculated pA2 value for the GABA-homotaurine interaction was 4.4 +/- 0.07. Neither GABA (10(-4) M) nor (+/-)-baclofen (10(-4) M) produced any significant inhibition of acetylcholine (2 X 10(-7) M) induced contractions of detrusor of strips from newborn rats, while atropine (3 X 10(-6) M) completely suppressed them. These results indicate that GABA inhibits field stimulation induced contractions of detrusor strips from newborn rats by activating prejunctional receptors (presumably of the GABAB subtype) which inhibit the release of acetylcholine from the postganglionic nerve endings.
已在成年和新生大鼠的逼尿肌条上研究了γ-氨基丁酸（GABA）对场刺激（0.1赫兹）诱发收缩的影响。在两个年龄组中，场刺激诱发的收缩不受六甲铵（10⁻⁵摩尔/升）影响，但几乎被河豚毒素（5×10⁻⁷摩尔/升）抑制。阿托品（3×10⁻⁶摩尔/升）显著抑制新生大鼠逼尿肌条的抽搐，但仅轻微抑制（10%或更低）成年动物的肌条抽搐。GABA（10⁻⁴）、高牛磺酸（10⁻³摩尔/升）或（±）-巴氯芬（10⁻⁴）均不影响成年大鼠逼尿肌条的抽搐。另一方面，GABA和（±）-巴氯芬对新生动物逼尿肌条抽搐的抑制程度大致相同（55 - 60%抑制）。高牛磺酸无显著作用。如果制备物预先暴露于低浓度GABA（5×10⁻⁶摩尔/升），GABA（10⁻⁴摩尔/升）和（±）-巴氯芬（10⁻⁴摩尔/升）对新生大鼠逼尿肌条抽搐产生的作用均会减弱，这表明存在脱敏现象。GABA对新生大鼠抽搐的抑制作用在10⁻⁷至10⁻⁴摩尔/升范围内呈浓度依赖性。GABAA受体拮抗剂印防己毒素（10⁻⁴摩尔/升）对GABA浓度反应曲线无影响，而GABAB受体拮抗剂高牛磺酸产生竞争性拮抗作用。GABA - 高牛磺酸相互作用的计算pA2值为4.4±0.07。GABA（10⁻⁴摩尔/升）和（±）-巴氯芬（10⁻⁴摩尔/升）均未对新生大鼠逼尿肌条乙酰胆碱（2×10⁻⁷摩尔/升）诱发的收缩产生显著抑制，而阿托品（3×10⁻⁶摩尔/升）则完全抑制了这些收缩。这些结果表明，GABA通过激活节前受体（推测为GABAB亚型）抑制新生大鼠逼尿肌条场刺激诱发的收缩，该节前受体抑制节后神经末梢乙酰胆碱的释放。
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