FIG. 2. Demonstrated actions of endogenously released opioid peptides in the hippocampus. A: Opioids inhibit GABA release from axon terminals of CA1/CA3 basket cells. B: Opioids inhibit glutamate release from perforant path axon terminals in the dentate gyrus and mossy fiber terminals in stratum lucidum. C: Opioids inhibit norepinephrine release from terminals of locus ceruleus afferents.