Extent and Timecourse of Pial Venous and Arterial Constriction During Cervical Sympathetic Stimulation in Cats

Cervical sympathetic stimulation (90 s, 15 Hz, 10 ms) was performed in 38 normoxic, normocapnic and normotensive cats under barbiturate and nitrous-oxide anaesthesia. Pial venous and arterial reactions were observed through closed cranial windows. Diameter variations of 261 venous and 166 arterial vessel portions were continuously analysed using a multichannel videoangiometer with an in vivo accuracy around 2%. Pial veins constricted by 12.7% and pial arteries by 11.9%. Veins > 150 μm resting diameter constricted significantly more than vessels ≤ 150μm. Veins started to constrict synchronously with arteries whereas arteries reached maximal constriction significantly earlier than veins. The venoconstriction, however, lasted longer than the arterial constriction and continued for about 20 seconds after the end of the stimulation.