Expression of a mussel 5-HT1 gene product is up-regulated by 5-HT
As shown in  Fig. 4A , a 1-hour incubation with 5-HT in vitro also induced a significant up-regulation of a transcript encoding a putative mussel 5-HT1 receptor (5-HT1) in haemocytes, while cell pre-treated with PROP significantly blocked the 5-HT effect on its receptor. In agreement, also haemocytes from mussels exposed in vivo to FX showed a significant up-regulation the 5-HT1 transcript ( Fig. 4B ). This effect was not observed in mussels exposed to the mixture FX+PROP ( Fig. 4B ).
10.1371/journal.pone.0061634.g004 Figure 4  Relative mRNA levels of a 5-HT1 receptor are affected by 5-HT or FX exposure.
(A) Relative 5-HT1 mRNA expression assessed in haemocytes incubated in vitro for 1 h with 1 µM 5-HT in the presence/absence of a 15-min pre-incubation with 100 µM PROP. Data are derived from three independent experiments (mean ± SEM); *p<0.05 between pairs of samples. (B) Relative 5-HT1 mRNA expression evaluated in haemocytes of mussels exposed in vivo for 7 days to FX (0.3 ng/L), PROP (0.3 ng/L) or to the mixture FX+PROP (0.3 ng/L+0.3 ng/L). A group of control (water) exposed mussels were included in the analysis. Data are reported as mean ± SEM. Different superscripts letters indicate statistically significant differences (p<0.05, N = 5).

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