Mean acetylcholine (ACh) release in the prefrontal cortex (PFC) during saline and ketamine injection. (A) No difference was seen between the two treatment groups during the wake phase. ACh release in the PFC was significantly decreased by isoflurane (Iso) administration (*). Injection of ketamine during Iso anesthesia did not result in any change in ACh levels compared to saline. However, after Iso was discontinued, ACh significantly increased (+) in ketamine-treated animals (n = 8) during recovery phase while animals in the saline group showed no significant difference. Compared to the saline group (n = 9), animals injected with ketamine showed a significant increase in ACh release during the recovery phase (#). Data are shown as mean ACh release (pmol) from PFC (+SD). (B) ACh release timeline in the PFC. No difference was seen between saline and ketamine injection during the wake, Iso, and Iso-after-injection phases. However, ketamine-treated animals showed a significant increase in ACh release within the PFC for the first 62.5 min during the recovery phase after discontinuation of Iso. Data are shown as mean ACh release from the PFC (± SD). Blue line = saline treatment; red line = ketamine treatment; statistical significance *,+,#P < 0.05.