Figure 4. Deletion of PERK in DA neurons alters striatal DA release and DAT activity in mice.

(a) Average single-pulse (1p) evoked [DA]_o transients recorded in CPu, NAc core, and NAc shell in PERK^f/f DAT-Cre versus control DAT-Cre mice at 3 months of age. (b-d) Summary plot of evoked [DA]_o peak expressed as % mean control in CPu (unpaired t-test, t₍₉₈₎ = 5.345, P < 0.001), NAc core (unpaired t-test, t₍₉₁₎ = 2.954, P < 0.01), and NAc shell (unpaired t-test, t₍₉₇₎ = 3.807, P < 0.001) in 3-month old mice. V_max values (maximum uptake velocity; e,g) and C_peak values (peak concentration; f,h) for DAT-mediated DA uptake derived from Michaelis-Menten analysis of single pulse evoked [DA]_o records determined using a fixed K_m of 0.9 μM for each brain region and genotype. (e) Summary plot of V_max values in CPu of WT DAT-Cre versus PERK^f/f DAT-Cre mice (unpaired t-test, t₍₉₄₎ = 5.589, P < 0.001). (f) Summary plot of C_peak values in CPu of WT DAT-Cre versus PERK^f/f DAT-Cre mice (unpaired t-test, t₍₉₄₎ = 5.113, P < 0.001). (g) Summary plot of V_max values in NAc core of WT DAT versus PERK^f/f DAT-Cre mice (unpaired t-test, t₍₉₀₎ = 3.616, P < 0.001). (h) Summary plot of C_peak values in NAc core of WT DAT versus PERK^f/f DAT-Cre mice (unpaired t-test, t₍₉₀₎ = 3.554, P < 0.001). Data are means ± s.e.m. of n mice, where n denotes the number of recording sites sampled from 3 to 5 mice per genotype; **P < 0.01; ***P < 0.001 for WT DAT-Cre vs. PERK^f/f DAT-Cre mice. Values with R² < 0.95, indicating goodness-of-fit were excluded from the data reported here. (i-k) In vivo pharmacological targeting of DA machinery reveals the impact of PERK deletion in DA neurons in mice. Acute i.p. injection of the D1 receptor antagonist (SCH 23390; 0.01 mg/kg) affects locomotor activity phenotype in WT DAT-Cre mice, but does not alter locomotor activity of PERK^f/f DAT-Cre mice. Conversely, high-dose SCH 23390 (0.2 mg/kg) impairs locomotor activity in both genotypes. (i) Summary plot of average number of steps during drag test (two-way ANOVA, genotype F_{(1, 51)} = 93.91, P<0.0001, treatment F _{(2, 51)} = 41.83, P<0.0001). (j) Summary plot of latency to fall from the rotating rod measured as average of two days (4 trials/day) test (two-way ANOVA, genotype F_{(1, 51)} = 112.8, P<0.0001, treatment F_{(2, 51)} = 18.19, P<0.0001). (k) Summary plot of spontaneous locomotor activity expressed as distance moved (cm) during the open field test (two-way ANOVA, genotype; F_{(1, 51)}= 46.80, P<0.0001, treatment F_{(2, 51)} = 34.66, P<0.0001). Mice were analyzed using two-way ANOVA followed by the Bonferroni’s test for multiple comparisons. *P < 0.05, **P < 0.01, ***P < 0.001. All data are shown as mean ± s.e.m. of n =10 (WT DAT-Cre) or 9 (PERK^f/f DAT-Cre) mice/treatment.