Systemic Administration of Docosahexaenoic Acid Suppresses Trigeminal Secondary Nociceptive Neuronal Activity in Rats

Background and Objectives: Docosahexaenoic acid (DHA) has been shown to modulate various voltage-gated ion channels and both excitatory and inhibitory synapses. Nonetheless, its exact effect on nociceptive signaling in the trigeminal system has yet to be elucidated. The purpose of the current investigation was to assess if acute DHA given intravenously to rats diminished the excitability of wide dynamic range spinal trigeminal nucleus caudalis (SpVc) neurons in response to mechanical stimulation in vivo. Methods: Single-unit extracellular activity was recorded from SpVc neurons in response to mechanical stimulation of the whisker pad in anesthetized rats. Responses to both non-noxious and noxious mechanical stimuli were analyzed in the present study. Results: The mean firing frequency of SpVc wide dynamic range neurons in response to both non-noxious and noxious mechanical stimuli was significantly dose-dependently inhibited by DHA, and the effect was seen within 5 min. After approximately 20 min, the inhibiting effects dissipated. Conclusions: These results suggest that, in the absence of inflammatory or neuropathic pain, the acute intravenous administration of DHA reduces the activity of trigeminal sensory neurons, including those responsible for pain, indicating that DHA could be utilized as an adjunct and alternative therapeutic agent for managing trigeminal nociceptive pain, including hyperalgesia.