Cerebrovascular effects of prostaglandin inhibitors in the gerbil.

Autoregulation of cerebral blood flow (CBF) to mean arterial blood pressure (MABP) of 40-50 mm Hg has been demonstrated in the spontaneously breathing gerbil anaesthetised with barbiturate (60 mg/kg). CO2 reactivity has also been assessed at 2.8% change CBF/mm Hg change in arterial PCO2. In six animals pretreated with indomethacin (3 mg/kg), autoregulation was preserved although the resting CBF was significantly reduced, but CO2 reactivity was completely abolished. 1-n-Butyl imidazole, a specific thromboxane synthetase inhibitor, was used in six other animals (3 mg/kg), and this abolished CO2 reactivity while preserving autoregulation; the effect of this agent has not been described previously. Both drugs inhibit different pathways of prostaglandin metabolism and may interfere with normal CO2 reactivity in several ways. Two explanations are that prostaglandins constitute the final common pathway in effecting cerebrovascular response to CO2 or, alternatively, that the free radicals and ionic fluxes generated during prostaglandin metabolism are a coincidental source of the hydrogen ion changes required.