Article Figures & Data
Figures
- Figure 1.
PRO enhances the maximal responses of hyperekplexic mutant GlyRs to glycine. A, Agonist-induced responses from oocytes expressing, wt α1 or α1(R271Q) GlyRs in the absence (left traces) or presence (right traces) of bath-applied PRO (1 μm) in the presence of submaximal glycine concentrations. Bars indicate the duration of glycine application; glycine concentrations are given in mm. B, Agonist-induced responses from oocytes expressing, from left, wt α1, α1(R271Q), or α1(R271K) GlyRs in the absence (left traces) or presence (right traces) of bath-applied PRO (0.5 mm) at saturating glycine concentrations. Bars indicate the duration of glycine application; glycine concentrations are given in mm. C, Dose-response curves for glycine in the absence (open circles) and presence (filled circles) of PRO (0.5 mm) for wt α1 and α1(R271K) GlyRs. Data points represent means from six experiments, normalized to Imax,Gly, obtained with either 1 or 100 mm glycine. Error bars (shown when larger than symbols) indicate SEM.
- Figure 2.
PRO enhances the maximal responses of wt and hyperekplexic α1 GlyRs to partial agonists. A, β-Alanine and glycine-induced responses recorded from oocytes expressing α1(R271K) GlyRs in the absence (-PRO) or presence (+PRO) of bath-applied PRO (0.5 mm). Bars indicate the duration of agonist application; agonist concentrations are given in mm. B, Pooled dose-response curves for β-alanine for α1 wt (circles) and α1(R271K) (squares) GlyRs in the absence (open symbols) and presence (filled symbols) of 0.5 mm PRO, respectively. Data are normalized to Imax,Gly obtained with saturating glycine concentrations (n = 5).
- Figure 3.
Behavioral effects of PRO in tg271Q-300 mice. A, PRO quiets tremor in hyperekplexic mice. Shown are typical 1 sec recordings obtained from wt and tg271Q-300 mice suspended by the tail from a mechanical transducer. In the upper traces, wt mice show no tremor activity before (solid line) and 3 min after (dotted line) a 15 mg/kg, i.p., injection of PRO. In the lower traces, untreated tg271Q-300 mice show high-frequency (25-30 Hz) tremors (solid line) that disappear 3 min after treatment with PRO. B, Acute pain responses to thermal stimuli in the hot-plate test. No significant differences in the latencies of withdrawal from thermal stimuli were observed between PRO-treated and control mice 3 and 8 min, after the intraperitoneal injection of 15 mg/kg PRO when using the hot-plate test (n = 11). C, PRO shortens the righting times of tg271-300 mice (white columns) without affecting those of wt mice (gray columns). Righting time latencies represent the time required for achieving a standing position either before (Control), or 3, 8, or 30 min after 15 mg/kg, i.p., injections of PRO. *p < 0.05 versus controls; **p < 0.01 versus controls (n = 11).
Tables
- Table 1.
Agonist response parameters obtained in two-electrode voltage-clamp experiments.
Fitted parameter α1 GlyRs α1(R271K) GlyRs Glycine (n = 8) β-Alanine (n = 5) Taurine (n = 3) Glycine (n = 5) β-Alanine (n = 5) −PRO +PRO −PRO +PRO −PRO +PRO −PRO +PRO −PRO +PRO EC50 (mm) 0.39 ± 0.05 0.037 ± 0.008* 2.02 ± 0.21 0.09 ± 0.02* 4.51 ± 1.96 0.14 ± 0.01 2.05 ± 0.07 0.18 ± 0.05* 5.77 ± 1.38 0.57 ± 0.16* EC50 ratio 10.5 22.5 32.0 11.6 10.2 ϵ 0.95 ± 0.01 0.93 ± 0.02 0.67 ± 0.05 0.92 ± 0.02* 0.23 ± 0.04 0.90 ± 0.04* 0.96 ± 0.01 4.1 ± 0.46* 0.12 ± 0.05 1.9 ± 0.47* ϵ ratio 1.0 1.4 3.9 4.3 15.8 -
EC50 and ϵ values were averaged from curve fits of individual experiments and are expressed as means ± SEM. *Different by p < 0.05 from the agonist-alone condition. +PRO, Responses recorded after 2 min of preincubation with 0.5 mm PRO.
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