Figure 7
Tonically-active GABA A Rs modify AP shape more strongly in wild-type GCs than in Ts65Dn GCs. (A) Superimposed APs (centred on their peak) from a wild-type (filled circle) and a Ts65Dn (filled triangle) GC before (thin line, control) and during inhibition of GABAARs with 10 μM SR95531 (thick line). Each trace is the average of 3 APs recorded at rheobase. (B) Under control conditions (con) AP height (dashed arrow, mean ± SEM) was greater in Ts65Dn GCs (*p = 0.0360, Student’s unpaired t test). SR95531 (SR) increased AP amplitude in wild-type (*p = 0.0125, Student’s paired t test; n = 24) but not in Ts65Dn GCs (p = 0.6553, Student’s paired t test; n = 13); in the presence of SR95531 AP heights in wild-type and Ts65Dn GCs were no longer different (*p = 0.2754, Student’s unpaired t test). (C) Traces in (A) vertically aligned on their threshold so as to aid shape comparison. (D) AP peak and AHP (afterhyperpolarisation) measured from threshold (mean ± SEM) before (con) and during application of SR95531 (SR). SR95531 increased the peak in wild-type (*p = 0.0167, Student’s t paired test) but not in Ts65Dn GCs (p = 0.7074, Student’s paired t test). SR95531 caused small decreases in AHP (wild-type, p = 0.0584; Ts65Dn, *p = 0.0107; Student’s paired t tests). (E) Maximum rate of AP rise (mean ± SEM) was speeded up by SR95531 in wild-type (*p = 0.00003, Student’s paired t test) but not Ts65Dn GCs (p = 0.1577, Student’s paired t test). (F) As in (E), but comparing maximum rates of fall (WT, *p = 0.0013; Ts65Dn, *p = 0.3116; Student’s paired t tests). (G) SR95531 shortened AP width in wild-type (*p = 0.0001, Student’s paired t test) but not in Ts65Dn GCs (p = 0.0132, Student’s paired t test).