Fig. 4

Cocaine self-administration and subsequent extinction reduced endogenous PPG mRNA expression in the NTS. a Expression of GLP-1 receptor mRNA transcripts in the VTA and PPG mRNA transcripts in the NTS was quantified following one (Ext1) and seven (Ext7) days of extinction following cocaine self-administration. No differences in GLP-1 receptor mRNA expression in the VTA were found after 1 day of extinction (n = 8) b or 7 days of extinction (n = 7) c in cocaine-experienced rats compared to yoked saline controls. d While not statistically significant (p < 0.09), there was a trend towards increased PPG mRNA expression in the NTS following 1 day of extinction (n = 7) in cocaine-experienced rats compared to control rats. e In contrast, statistically significant decreases in NTS PPG mRNA expression were found following 7 days of extinction in cocaine-experienced rats compared to yoked saline controls. *p < 0.01, unpaired t-tests