AUTOREGULATION IN THE MIDDLE MENINGEAL ARTERY

In cats anesthetized with alpha-chloralose, autoregulation of blood fl ow (F) in the middle meningeal and common carotid arteries was assesse d by bleeding and subsequently reinfusing the animals to achieve a 25% step reduction in mean arterial blood pressure (P), while maintaining the systolic blood pressure >80 mmHg. The integrity of autoregulation was assessed by calculating the gain factor G(f) = 1 - [(Delta F/F)/( Delta P/P)]. Cats were examined intact, after hexamethonium (10 mg/kg) , and after papaverine (6 mg/kg). Reduction of blood pressure of 25 to 60 mmHg produced equivalent drops in carotid blood flow (G(f) = 0.041 +/- 0.34; mean +/- standard deviation, n = 12). There were only small changes in flow in the middle meningeal artery during this procedure (G(f) = 0.91 +/- 0.29). Hexamethonium did not block autoregulation in the middle meningeal artery (G(f) = 0.92 +/- 0.13, n = 4). However, pa paverine almost completely abolished the ability of the artery to auto regulate (G(f) = 0.10 +/- 0.16, n = 7). The results suggest that the m iddle meningeal artery possesses an ability similar to that of the cor tical circulation to autoregulate its blood flow through intrinsic, no n-neuronal mechanisms. This will have important implications for the s tudy of disturbances of dural arterial control in migraine and other h eadaches.