Failure of memantine to “reverse” quinpirole-induced hypomotility

Figure 1 Spontaneous motor activity after 24 h discontinuation of chronic treatments (60 min habituation to the motility cage). Each value represents the mean ± SEM from 20 rats: Vehicle (VEH), memantine (MEM), imipramine (IMI). Number of long movements (A), rearing (B) and short movements (C) measured as indicated in the materials and methods: Motor activity. A: ^fP < 0.001, memantine vs vehicle [F (1.51) = 12.21; P = 0.0009]; ^bP < 10^-6, imipramine vs vehicle [F (1.51) = 31.71; P = 0.000001]; B: ^dP < 0.01, memantine vs vehicle [F (1.51) = 10.58; P = 0.0020]; ^hP < 10^-4, imipramine vs vehicle [F (1.51) = 19.90; P = 0.000045]; C: ^dP < 0.01, memantine vs vehicle [F (1.51) = 11.57; P = 0.0013]; ^dP < 0.01, imipramine vs vehicle [F (1.51) = 10.13; P = 0.0024]; ANOVA followed by Newman-Keuls-test.

Figure 2 Motor response to quinpirole after 24 h chronic imipramine and memantine withdrawal. Number of long movements (A), rearing (B) and short movements (C) measured as indicated in the materials and methods: Motor activity. Each value represents the mean ± SEM from 10 rats (ANOVA followed by F test for contrast). Control vehicle (CV), quinpirole (QUI). A: ^bP < 0.01, Vehicle-CV vs vehicle-QUI [F (1.48) = 11.20; P = 0.0015]; ^aP≤ 0.05, memantine-CV vs memantine-QUI [F (1.48) = 3.74; P = 0.05]; ^aP≤ 0.05, imipramine-CV vs imipramine-QUI [F (1.48) = 3.74; P = 0.05]. ^cP≤ 0.05, vehicle-QUI vs imipramine-QUI [F (1.48) = 6.39; P = 0.014]; ^eP < 0.01, memantine-QUI vs imipramine-QUI [F (1.48) = 7.74; P = 0.007]; vehicle-QUI vs memantine-QUI [F (1.48) = 0.07; n.s]; B: ^dP < 10^-4, vehicle-CV vs vehicle-QUI [F (1.48) = 22.73; P = 0.000018]; ^aP≤ 0.05, memantine-CV vs memantine-QUI [F (1.48) = 4.10; P = 0.048]; imipramine-CV vs imipramine-QUI [F (1.48) = 0.006; n.s.]. ^cP≤ 0.05, vehicle-QUI vs imipramine-QUI [F (1.48) = 3.80; P = 0.05]; vehicle-QUI vs memantine -QUI [F (1.48) = 22.48; n.s]; C: ^bP≤ 0.01, vehicle-CV vs vehicle-QUI [F (1.48) = 6.83; P = 0.01]; imipramine-CV vs imipramine -QUI [F (1.48) = 0.24; n.s.]. ^cP≤ 0.05, vehicle-QUI vs imipramine-QUI [F (1.48) = 4.83; P = 0.032]; ^cP≤ 0.05 memantine-QUI vs imipramine-QUI [F (1.48) = 3.75; P = 0.05].

Figure 3 Time course of quinpirole effect on motor activity after 24 h chronic imipramine and memantine withdrawal. Long movements (A), rearing (B) and short movements (C) measured as indicated in the materials and methods: Motor activity. Each value represents the mean ± SEM from 10 rats: vehicle + quinpirole (VEH Q), memantine + quinpirole (MEM Q), imipramine + quinpirole (IMI Q). A, B: ^bP < 0.01 imipramine-quinpirole vs vehicle-quinpirole and memantine-quinpirole; C: ^aP < 0.05 imipramine-quinpirole vs memantine-quinpirole (ANOVA followed by F test for contrast; horizontal lines represent contrast involving consecutive times).