Effect of baclofen on plasma GH levels in controls and AD. Data are mean ± S.E.M. (A) Effect of placebo, 10 and 60 mg baclofen on GH levels in controls. A significant effect of time, dose and a dose by time interaction was observed [n = 8, Time: F(6, 48) = 10.44, P < 0.0001, Dose: F(2, 16) = 11.34, P = 0.0009, Dose × Time: F(12, 96) = 10.16, P < 0.0001]. *60 mg > placebo, #10 mg > placebo (P < 0.05, Tukey's multiple comparison test). (B) Effect of placebo, 60 and 90 mg baclofen on GH levels in AD. *90 mg > placebo (P < 0.05, Tukey's multiple comparison test). (C) Differential effect of baclofen on plasma GH levels in controls and AD. A significant effect of group [F(1, 18) = 15.36, P = 0.001], time [F(6, 108) = 16.35, P > 0.0001] and a dose × time interaction [F(6, 108) = 10.31, P < 0.0001] were observed. *Control > AD (P < 0.05, Sidak's multiple comparison test). Differential effects on GH in younger controls (cohort 1, n = 9, dashed line) and older controls (cohort 2, n = 3, dotted line) are also depicted in (C). There was no significant difference between GH levels following baclofen in younger and older control cohorts at any time point, and the significant differences between AD and both young and old controls remained (mixed ANOVA with Sidak's multiple comparison test). The average age of the younger cohort was 24.7 ± 4.7 years, compared with the older cohort (average age 52.0 ± 6.1) and the AD group (53.1 ± 8.9 years).