Independent Regulation of Periarteriolar and Perivenular Nitric Oxide Mechanisms in the In Vivo Hamster Cheek Pouch Microvasculature

Objective: We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre- and postcapillary segments of the microcirculation in the hamster cheek pouch. Materials and Methods: We applied acetylcholine (ACh) or platelet-activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO-sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF. Results: ACh increased periarteriolar [NO] significantly in a dose-dependent manner. ACh at 1 M increased [NO] from 438.143.4 nM at baseline to 647.966.3 nM, while 10 M of ACh increased [NO] from baseline to 1,035.059.2 nM (P0.05). Neither 1 nor 10 M of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.650.8 to 622.841.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.62.1 to 455.519.9 in CVEC, while ACh had no effect. Conclusions: We conclude that NO production can be stimulated in a differential manner in pre- and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules.