Effect of propofol on arachidonate cascade by vasopressin in aortic smooth muscle cells: inhibition of PGI2 synthesis

Development of a radioligand for imaging V1a vasopressin receptors with PET

A series of vasopressin receptor V_1a ligands have been synthesized for positron emission tomography (PET) imaging. The lead compound (1S,5R)-1 ((4-(1H-indol-3-yl)-3-methoxyphenyl) ((1S,5R)-1,3,3-trimethyl-6-azabicyclo[3.2.1]octan-6-yl)methanone) and its F-ethyl analog 6c exhibited the best combination of high binding affinity and optimal lipophilicity within the series. (1S,5R)-1 was radiolabeled with ¹¹C for PET studies. [¹¹CH₃](1S,5R)-1 readily entered the mouse (4.7% ID/g tissue) and prairie vole brains (∼2% ID/g tissue) and specifically (30-34%) labeled V_1a receptor. The common animal anesthetic Propofol significantly blocked the brain uptake of [¹¹CH₃](1S,5R)-1 in the mouse brain, whereas anesthetics Ketamine and Saffan increased the uptake variability. Future PET imaging studies with V_1a radiotracers in non-human primates should be performed in awake animals or using anesthetics that do not affect the V_1a receptor.

Propofol-induced relaxation of rat aorta is altered by aging

BACKGROUND

Propofol causes vasodilation via endothelium-dependent and -independent mechanisms. Because endothelial function is impaired with aging, the effects of propofol on endothelium-dependent vasodilation might be altered by aging. The aim of this study was thus to determine the effects of aging on vascular responses to propofol.

METHODS

Young (4-6 weeks old) or adult (16-25 weeks old) rats were anesthetized with sevoflurane. The thoracic aorta was dissected and cut into pieces 3-4 mm in length. In some rings, the endothelium was deliberately removed. The ring segment of the aorta was mounted for isometric force recording at a resting tension of 0.5-1.0 g in a 2 ml organ bath, containing Krebs-Ringer bicarbonate buffer. Arteries were precontracted with phenylephrine, and the function of endothelium was confirmed with acetylcholine. Then, we studied the concentration-dependent effects of propofol in endothelium-intact (control group) and -denuded aortic rings (denuded group), as well as those treated with N(ω)-nitro-L-arginine methylester (L-NAME group).

RESULTS

Relaxation due to propofol was observed in the control groups of both young and adult rats in a concentration-dependent manner, but the magnitude of relaxation was significantly greater in young rats. In addition, in young rats, relaxation due to propofol was significantly and equally reduced in both L-NAME and denuded groups at all propofol concentrations that we studied (10(-6)-10(-3) M). In adult rats, relaxation due to propofol was quite similar between control and L-NAME groups at all propofol concentrations, whereas it was significantly reduced in the denuded group.

CONCLUSION

These results suggest that endothelium-derived nitric oxide plays an important role in propofol-induced vasodilation in young rats, but not in adult rats.