(A), Injection protocol for naloxone treated animals. (B) LTPGABA in a dopamine cell from an animal administered saline 15 minutes prior to swim stress; slices were prepared 24 hrs after stress. Insets, representative IPSCs before (Control) and 30 minutes after SNAP application (SNAP). (C) Rescue of SNAP-induced LTPGABA in a slice from an animal treated with naloxone prior to stress. (D) Averaged experiments (saline-treated rats, n = 17; naloxone-treated rats, n = 9). (E) Injection protocol for nor-BNI treated animals; nor-BNI is effective for over a week following injection (Endoh et al., 1992). (F) Absence of LTPGABA in a dopamine cell from an animal administered saline 24 hrs prior to stress and (G) from an animal pretreated with nor-BNI 24 hours prior to stress. (H) Averaged experiments (saline-treated rats, n = 8; nor-BNI-treated rats, n = 8). Scale bars: 20 ms, 100 pA.