Fig. 2.

Differential vulnerability of 5-HT axons in NAc shell and core. Dark-field images (coronal) show the effects of Meth (4 × 20 mg/kg) or PCA (2 × 10 mg/kg) on 5-HT-IR (A–C) and SERT-IR (D–F) axon terminals in the caudal division of the nucleus accumbens (interaural 10.0 mm). In control animals the 5-HT axons in NAc core and dorsal striatum express SERT, whereas most axons in the caudal shell are SERT-negative. After treatment with either drug, 5-HT axons in the core and dorsal striatum are ablated, whereas those in the shell are spared, demonstrating that SERT-negative axons are selectively resistant to amphetamine neurotoxicity. Drug-treated animals were killed 14 d after treatment, and sections were processed for immunocytochemistry. A, D, Saline-treated; B, E, Meth-treated; C, F, PCA-treated. Scale bar, 300 μm. ac, Anterior commissure; AcC, nucleus accumbens core; AcS, nucleus accumbens shell;DStr, dorsal striatum. (Note: “dorsal striatum” in the rat refers to the caudate–putamen complex as distinct from ventral striatum.)