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PLATELET-ACTIVATING FACTOR AFFECTS NOCICEPTION IN RATS AT CEREBRAL SITES OF ACTION

Systemic administration of selective platelet-activating factor (PAF) antagonists that block either plasma membrane or intracellular PAF binding sites attenuate the late-phase nociceptive response to formalin in rats. Inasmuch as these antagonists both cross the blood-brain barrier, and selectively attenuate the late-phase of nociception, we have suggested that PAF may be an important central mediator of inflammatory-based pain. In the present study we investigated the effect of central administration of PAF antagonists on formalin-induced nociception. Intra-cerebral ventricular (i.c.v.) injections of either BN 52021 (a plasma membrane PAF receptor antagonist) or BN 50730 (an intracellular PAF binding site antagonist) diminished the late-phase nociceptive response to formalin. These findings suggest that PAF acts within the central nervous system (CNS)-at both plasma membrane and intracellular sites-to mediate inflammatory-based pain processing.