Figure 3.

Non-mu opioid and GABA_A receptors modulate acetylcholine (ACh) release in the principal sensory trigeminal nucleus (PSTN). A. The significant (*) increase in PSTN ACh release caused by morphine (MSO₄) was not blocked by the opioid antagonist naloxone (MSO₄ + Nal) but was blocked by coadministration of the kappa opioid antagonist nor-binaltorphimine (MSO₄ + norBNI). B. Relative to control (dialysis with Ringer's solution), the GABA_A receptor antagonist bicuculline significantly (*) increased ACh release in the PSTN. The data in A and B were obtained from 12 rats, and each drug condition summarizes results from 3 rats.