Figure 1.

Effect of the 5‐HT₄ ligands prucalopride and GR 125487 on L‐DOPA‐induced DA release in the striatum, the prefrontal cortex, the substantia nigra pars reticulata, and the hippocampus of 6‐OHDA rats. Data represent the mean ± standard error of the mean (SEM) of DA extracellular levels in each sample (n = 4–5 animals/group) and are expressed in raw data (pg/10 μL of sample). Three to four weeks after the unilateral injection of 6‐OHDA in the median forebrain bundle, L‐DOPA or its vehicle (0) was administered intraperitoneally (i.p.) at 12 mg/kg (time indicated by the vertical arrows) and was preceded 20 min before by the i.p. administration of benserazide (15 mg/kg, i.p.) 7. The 5‐HT₄ compounds, prucalopride and GR 125487, were administered intraperitoneally 20 min before L‐DOPA (as benserazide) at 5 and 0.1 mg/kg i.p., respectively 8. All drugs were freshly prepared and dissolved as the free base (excepted benserazide) in saline. The effect of 5‐HT₄ compounds was studied on the overall effect of L‐DOPA using one‐way ANOVA using group as the main factor. It reached significance in the SNr [F(2,12) = 4.7, P < 0.05] and the PFC [F(2,13) = 5.4, P < 0.05] but not in the striatum [F(2,13) = 0.6, ns] or the HIPP [F(2,13) = 0.5, ns]. Asterisks refer to the overall statistical effect * P < 0.05 versus vehicle + L‐DOPA group (Fisher's PLSD test).