Furthermore, 5-HT2CR immunoreactivity was evidenced throughout both SN sub-regions (see green in montage) as predicted by prior evidence at this brain level (Eberle-Wang et al., 1997). Open in a separate window Figure 3 Immunohistochemical localization of GAD-67 and 5HT2C receptors (5HT2CRs) in the substantia nigra (SN) of rats. An immunohistochemical study was also performed to determine whether 5-HT2C receptors were localized on GABA neurons in both of the SNpr subregions examined in this study. Methods Animals Naive male Sprague-Dawley rats (Harlan, Indianapolis, IN, USA), weighing between 200 and 400 g at the time of surgery, were used for all experiments. Rats were housed three per cage in a temperature-controlled room with a 12/12 h light/dark cycle. Food and water were available blocked by SB 242084 infusions into the mid-SNpr (Fig. 2A). A two-way ANOVA (drug time) found a significant interaction [ 0.001] as well as significant main effects for drug treatment [= 0.018] and time [ 0.001]. To better understand the interaction, one-way repeated measures ANOVAs on Bis-NH2-C1-PEG3 data (time) from each drug group were then conducted. Ro 60-0175 administration progressively decreased striatal DA relative to baseline [= Bis-NH2-C1-PEG3 0.010], reaching significance at 150, 180, and 210 min post-injection (Dunnetts test, 0.05).Vehicle did not alter striatal DA. Infusions of SB 242084 into the SN produced a slight increase in dialysate DA [= 0.016], but a Dunnetts post-hoc test revealed that no individual time points differed from baseline DA levels. SB 242084 + Ro 60-0175 co-treatment altered striatal DA [ 0.001]. However, SB 242084 infusions in Rabbit polyclonal to ARHGAP15 these animals failed to block, and in fact significantly potentiated the effects of Ro 60C0175, as the last five timepoints in these animals differed from baseline (Dunnetts test, 0.05). Average basal levels for this experiment were 4.29 pg/20 l. Open in a separate window Figure 2 Effects of intranigral or intrastriatal infusions of the 5-HT2C antagonist SB 242084 on decreases in striatal DA release produced by the systemic administration of the 5-HT2C agonist Ro 60-0175 (3 mg/kg). Data are indicated as percent baseline SEM. Horizontal pub indicates time during which SB 242084 was perfused through the probe. Arrow shows the time of injection of R0 60-0175. *Indicates 0.05 vs. baseline levels. SNpr = substantia nigra pars reticulate; VEH = vehicle. A: Infusions of SB 242084 (1.0 M) into the mid-SNpr potentiated the decreases in striatal DA efflux produced by administration of Ro 60-0175. *Indicates 0.05 vs. baseline levels (Dunnetts post-hoc test). n = 8C11/group. B: Infusions of SB 242084 (0.1 M) by an angled probe into the SNpr slightly increased striatal DA but did not reverse the decreases in striatal DA efflux produced by administration of Ro 60-0175. *Indicates 0.05 vs. baseline levels (Dunnetts post-hoc test). n = 6C7/group. C: Infusions of SB 242084 (1.0 M) by an angled probe placement into the SNpr partially reversed the decreases in striatal DA efflux produced by administration of Ro 60-0175. *Indicates Bis-NH2-C1-PEG3 0.05 vs. baseline levels (Dunnetts post-hoc test). n = 5C7/group. D: Infusions of SB 242084 (1.0 M) into the striatum increased striatal DA; the combination of Ro 60-0175 + SB 242084 resulted in no net effect. n = 6C11/group. Experiment 1b: Reverse dialysis of the 5-HT2C antagonist SB 242084 into the SNpr, adjacent to the SNpc, partially blocks 5-HT2C agonist Ro 60C0175-induced decreases in striatal DA To account for possible regional variations in the distribution of 5-HT2C receptor manifestation within the SN, a second experiment was carried out using different coordinates. This experiment used an angled probe placement in the SN, where drug could theoretically diffuse into the lateral SNpr. All experimental methods were carried out exactly as they were in the 1st experiment. Two concentrations of SB 242084, 0.1M or 1.0M, were employed in independent organizations. 0.1 M concentration of SB 242084 Intranigral infusions of SB 242084 did not block Ro 60C0175-induced decreases in striatal DA (observe Fig. 2B). A two-way ANOVA (time drug) yielded Bis-NH2-C1-PEG3 a significant connection [ 0.001], as well as significant main effects for time [ 0.001].