Volatile anesthetics like isoflurane may cause unconsciousness by binding to microtubules (MTs) inside neurons and dampening their quantum optical effects. In male rats injected with the MT-stabilizing drug epothilone B (epoB), loss of righting reflex under 4% isoflurane took an average of 69 seconds longer than in rats given a placebo. The difference was statistically significant with a large effect size (Cohen's d = 1.9) and could not be explained by tolerance from repeated anesthetic exposure. This supports the idea that consciousness arises from quantum physical states in neural microtubules, as proposed in the orchestrated objective reduction (Orch OR) theory.
Stabilizing brain microtubules can make animals resistant to anesthesia. Mice given a single dose of a microtubule-stabilizing drug showed a 29-second delay in losing consciousness under isoflurane the next day. This significant within-subject effect, with a Cohen's d of 0.8, suggests that anesthetic binding to microtubules contributes to unconsciousness. This supports theories proposing consciousness arises from quantum states within these neural structures, and hints at potential sex differences in anesthetic mechanisms.