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The role of the insular cortex (IC) in pain processing has been suggested in both human and animal studies. Electrical stimulation of the human IC induces painful sensations. Also, painful stimuli activate the IC. The aim of this work is to determine if electrical stimulation of the IC modifies nociceptive behaviour and if this modification correlates with EEG features. For rat IC stimulation, a bipolar steel electrode was implanted. The stimulation parameters were: square pulses of 0.2 ms at 100Hz for 1 s every 5 s. The stimulation was applied 10 min daily over 5 days. Immediately after electrical stimulation, acute thermal stimulation was applied with a plantar test apparatus to measure nociception as paw withdrawal latency (PWL) and EEG recordings were performed. After five days of IC electrical stimulation, secondary inflammatory hyperalgesia was induced by an intraplantar injection of carrageenan (CAR) 1% in 250 mml and PWL was measured.

The results show that IC stimulation significantly increases PWL after the induction of both acute thermonociception and secondary inflammatory hyperalgesia. Also, the change in spectral measures of electrical activity in the IC consisted of increased relative power of the theta frequency band (3–7Hz). IC increases potency in low frequencies which may correlate with a decreased nociceptive behaviour. This work highlights the role of the IC in the modulation of acute thermonociception and secondary inflammatory hyperalgesia.