title: Evidence for different exocytosis pathways in dendritic and terminal dopamine release in vivo.
abstract: Although dendritic release was first proposed in the 1970s, the mechanism of release is still subject to debate. We have used in vivo microdialysis to study the acute effects of botulinum toxin A, B and tetanus toxin injected in the substantia nigra or striatum of freely moving rats. Spontaneous and evoked dopamine release decreased in both regions after treatment with the SNAP-25 (synaptosome-associated protein of 25 kDa) cleaving protease botulinum toxin A (1000 mouse lethal doses, MLD). Tetanus toxin (4000 MLD) did not significantly change spontaneous or evoked dopamine release in striatum or in the substantia nigra. Another synaptobrevin cleaving protease, botulinum toxin B, inhibited release in the striatum by 55% but did not affect dopamine release when injected in the substantia nigra. The results indicate that both terminal and somatodendritic dopamine release need intact SNAP-25 to occur, but somatodendritic dopamine release in contrast to terminal release depends on a botulinum toxin B resistant pathway.
authors.affiliation: Department of Pharmacology, Institute of Physiology and Pharmacology, Göteborg University, Box 431, SE 405 30, Göteborg, Sweden. filip.bergquist@pharm.gu.se
authors.forename: Filip
authors.initials: F
authors.lastname: Bergquist
authors.forename: Haydeh Shahabi
authors.initials: HS
authors.lastname: Niazi
authors.forename: Hans
authors.initials: H
authors.lastname: Nissbrandt
mesh_terms: D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D019274:Botulinum Toxins, Type A; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D003712:Dendrites / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism; D013744:Tetanus Toxin / Q000494:pharmacology
chemical_list: D013744:Tetanus Toxin; C096323:rimabotulinumtoxinB; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A; D004298:Dopamine