The acute cardiorespiratory effects of centrally injected arachidonic acid; the mediation of prostaglandin E, D and F 2α .

Arachidonic acid (AA), which is released from synaptic membrane phospholipid by neuroreceptor-initiated activation of phospholipase A2 , is abundant in the brain and works as a neurotransmitter and/or neuromodulator in the central nervous system. Recently we reported that centrally injected AA generated pressor and hyperventilation effects by activating thromboxane A2 (TXA2 ) signaling pathway. The present study was designed to investigate the mediation of other metabolites of AA such as prostaglandin (PG) D, PGE and PGF2α alongside TXA2 in the AA-evoked cardiorespiratory effects in anaesthetized rats. Intracerebroventricular (i.c.v.) administration of AA caused pressor, bradycardic and hyperventilation responses by increasing pO2 and decreasing pCO2 in adult male anaesthetized Sprague Dawley rats. Pretreatment (i.c.v) with different doses of DP/EP prostanoid receptor antagonist, AH6809 or FP prostanoid receptor antagonist, PGF2α dimethylamine partially blocked the cardiorespiratory and blood gas changes induced by AA. In conclusion, these data plainly report that central PGD, PGE or PGF2α might mediate, at least partly, centrally administered AA-evoked cardiorespiratory and blood gas responses.