In addition to their critical role in neurotransmitter dynamics, activated astrocytes also secrete neurotrophic factors, e.g., glial-derived neurotrophic factor (GDNF) (Appel et al. 1997; Lee et al. 2006). GDNF is neuroprotective for medial striatal and VTA dopaminergic neurons on exposure to psycho-stimulants (Cass 1996; Boger et al. 2007). Intra-VTA GDNF infusion blocks numerous biochemical and behavioural sequelae of chronic cocaine and morphine misuse; conversely, intra-VTA anti-GDNF antibodies augment cocaine-induced stereotypy (Messer et al. 2000). Finally, infusion of the dipeptide leucine-isoleucine – an identified GDNF and tumour necrosis factor alpha (TNF-α) inducer of expression – inhibits psychostimulant-induced CPP and sensitization (Niwa et al. 2007).
