Fig. 4.

Administration of exendin-4 into the nucleus accumbens shell attenuates oxycodone self-administration and does not alter the thermal antinociceptive effects of oxycodone. Microinjection sites in the ventral striatum for oxycodone self-administration experiments in which rats were pretreated with vehicle or exendin-4 (a). In FR5 test sessions, total active lever responses (b) and total oxycodone infusions (c) were significantly attenuated in rats (n = 12/treatment) pretreated with 0.05 µg exendin-4 versus vehicle in the shell (*p < 0.05, Bonferroni). In PR test sessions, total active lever responses (d) were significantly decreased in rats (n = 10/treatment) pretreated with 0.05 µg exendin-4 versus vehicle in the shell (*p < 0.05, Bonferroni). Total oxycodone infusions (e) and breakpoints (f) were decreased in rats pretreated with 0.005 and 0.05 µg exendin-4 versus vehicle in the shell (*p < 0.05, Bonferroni). g Tail-flick latencies were significantly increased following oxycodone self-administration test sessions compared to baseline measurements (*p < 0.05), indicating a thermal analgesic response. h No effects of intra-accumbens shell exendin-4 were found on the percentage of maximum possible effect (%MPE), indicating that activation of GLP-1 receptors in the shell does not alter oxycodone-induced analgesic responses in this model (n = 7/treatment)