Cyclooxygenase-pathway participates in the regulation of regional cerebral blood flow in response to neuronal activation under normo- and hypercapnia.

The present study was designed to investigate whether cyclooxygenase products are involved in the regulation of the regional cerebral blood flow, evoked by somatosensory activation (evoked rCBF) under normo- and hypercapnia. Indomethacin (IMC) was used as cyclooxygenase inhibitor. It was applied intravenously (i.v., 10 mg/kg/h) in two experimental protocols-before hypercapnia (i) and after hypercapnia (ii). Somatosensory activation was induced by electrical hind paw stimulation (5 Hz frequency, 5 s duration, 1.5 mA). The evoked rCBF-response was measured in alpha -chloralose anesthetized rats using laser-Doppler flowmetry. IMC abolished completely the effect of hypercapnia on the baseline level of CBF. The drug reduced significantly evoked rCBF-response also. The inhibitory effect of IMC on evoked rCBF-response is better expressed under normocapnia (approximately 70%) than that under hypercapnia (approximately 40%). After IMC application, the normalized evoked rCBF curves peaked earlier as compared to that before its application (P<0.05), although the rise time of 0.5 s was nearly constant regardless of stimulus frequency. In conclusion, the results suggest a participation of IMC-sensitive and cyclooxygenase-dependent mechanisms in the regulation of evoked rCBF, induced by somatosensory stimulation.