Abstract Body: Aims: Recent studies have implicated the use of prescription opioids as a risk factor for cardiovascular diseases (CVD), with associations including myocardial infarction, coronary artery disease and vascular deterioration. Further, opioid-dependent patients show increased vascular aging and arterial stiffness when compared to opioid-naïve controls. Our hypothesis was that rats dependent on remifentanil (a fentanyl analog) after a 12-day operant self-administration (SA) study lead to vascular dysfunction in thoracic aorta. Because erectile dysfunction (ED) is associated with arterial stiffness and is positively correlated with its severity, we hypothesized that opioid SA impaired corpus cavernosum (CC) reactivity as well.

Methods: Male Wistar rats (12 weeks-old) were implanted with intravenous catheters and learned to lever press (FR1) for remifentanil (1µg/kg/infusion). A separate group of rats received passive yoked infusions of saline administered in synchrony with remifentanil-treated animals to control volumetric vascular effects. Following administration, animals were euthanized, and aorta and CC collected to evaluate function using both pin and strip myographs. Concentration-response curves to phenylephrine (Phe; 10^-11-10^-4M), sodium nitroprusside (SNP) and acetylcholine (Ach or SNP; 10^-10-10^-4M) were performed to test contractility and endothelium-independent and -dependent relaxation respectively.

Results: Remifentanil-treated rats showed rapidly acquired SA behavior, exhibiting robust and selective drug-paired lever pressing when compared to the non-drug paired lever. In contrast, yoked saline-treated controls rarely exhibited lever pressing. Endothelium-dependent relaxation in the aorta was diminished in the remifentanil group (Rmax: Control: 68.7±2.7 vs. Remi: 47.8±3.7%; p<0.05). There were no observed alterations in endothelium-independent relaxation or vascular contraction. However, CC contraction was slightly shifted to the right in remifentanil treated rats (pEC₅₀: Control: 6.04±0.09 vs. Remi: 5.66±0.12; p<0.05). No changes were observed in the CC relaxant response. These findings indicate that 12 days of remifentanil administration results in endothelial dysfunction in large arteries and impaired cavernosal reactivity. Long-term exposure may lead to aortic stiffness exacerbating ED severity and increases in pulse-wave velocity in opioid-dependent patients contributing to the onset of hypertension.