Figure 2
From: The Role of Peripheral Opioid Receptors in Triggering Heroin-induced Brain Hypoxia
Mean (±SEM) changes in heroin-induced oxygen responses in the NAc (A–C) and subcutaneous space (D) following sc injections of saline (A), naloxone-HCl (B; 0.2 mg/kg), and naloxone-MET (C,D; 2 mg/kg) in freely moving rats. Values significantly different from baseline are shown as filled symbols; n indicates the number of averaged tests. Vertical dotted lines with black arrows show the moments of iv heroin injections and horizontal doted lines show baselines. Right panels with bar graphs show the strength of immediate changes in NAc oxygen calculated as the area under the curve for the time interval of oxygen decrease induced by the initial heroin injection. Negative values represent oxygen decrease and positive values represent oxygen increase. Asterisks show significant differences vs. the first heroin injection before administration of each testing drug (*p < 0.05 and **p < 0.01). Second graphs in each row show NAc oxygen responses following sc injection of testing drugs (saline and two naloxone analogs).
