The effects of analgesic supplements on neural activity in the main olfactory bulb of the mouse

We evaluated ketoprofen, a nonsteroidal anti-inflammatory drug (NSAID), as an antinociceptive supplement to chloral hydrate anesthesia in mouse. Effects of ketoprofen on main olfactory bulb (MOB) neuronal spontaneous activity were investigated using extracellular recordings in mouse in vivo. These effects were compared with those of another nociceptive supplement, the mu-opioid agonist buprenorphine. Ketoprofen (100 or 200 mg/kg) did not significantly alter MOB single-unit spontaneous rates in either ICR or C57BL/6J mice. In contrast, buprenorphine, at doses of 0.02, 0.05, and 0.20 mg/kg, inhibited MOB neuronal spontaneous rates by 19%, 49%, and 57%, respectively. Neither drug altered the temporal patterning of single-unit spike trains, as measured by the interspike interval (ISI) coefficient of variation (CV). We also investigated the ability of ketoprofen and buprenorphine to induce antinociception in the anesthetized mouse. The electroencephalogram (EEG) was used to measure the anesthetic plane. Both ketoprofen and buprenorphine altered the EEG trace and ketoprofen altered the power spectrum in a manner consistent with deepening anesthesia. Lastly, when applied at the time of anesthesia induction, ketoprofen decreased the amount of chloral hydrate necessary to maintain a defined anesthetic plane during the rest of the experiment. These results suggest that ketoprofen induces antinociception under chloral hydrate anesthesia without significantly inhibiting spontaneous activity of MOB neurons. Ketoprofen is therefore suitable as an antinociceptive supplement to chloral hydrate anesthesia during in vivo electrophysiologic recordings of the mouse MOB.