Fig. 8

33HPP modulates the food reward system and alters the memory. a Nucleus accumbens mRNA expressions of dopamine receptor 2 (Drd2), dopamine receptor 1 (Drd1), tyrosine hydroxylase (Th), dopamine transporter (Dat), b µ-opioid receptor (Oprm), κ-opioid receptor (Oprk), δ-opioid receptor (Oprd), and pre-prodynorphin (Pdyn) measured by qPCR in mice injected with TBS (TBS) and with 3-(3’-Hydroxyphenyl)propanoic acid (33HPP). Operant conditioning test showing c the number of active lever presses, d the number of inactive lever presses, and e the ratio between the number of inactive lever presses on the number of active lever presses during the progressive ratio sessions (PR) by mice injected with TBS (TBS) and mice injected with 33HPP (33HPP). f Hippocampal mRNA expressions of Drd2, Drd1, Th, and Dat in mice injected with TBS (TBS) and mice injected with 33HPP (33HPP). Data are shown as mean ± SEM (n=6/group). p-values were obtained after unpaired Student’s t test or non-parametric Mann-Whitney test