title: Dopamine release evoked by beta scorpion toxin, tityus gamma, in prefrontal cortical slices is mediated by intracellular calcium stores.
abstract: 1. We have investigated the effect of tityus gamma (TiTX gamma) scorpion toxin on the release of [3H]dopamine in rat brain prefrontal cortical slices. The stimulatory effect of TiTX gamma on the release of [3H]dopamine was dose/time-dependent with an EC50 of 0.01 microM. 2. Tetrodotoxin blocked the TiTX gamma-induced release of [3H]dopamine, indicating the dependency for Na+ channels. 3. EGTA had no effect on the TiTX gamma-induced release of [3H]dopamine, indicating the process is independent of extracellular calcium. Release of [3H]dopamine evoked by TiTX gamma was inhibited by 57% by BAPTA, a chelator of intracellular calcium. 4. Xestospongin and 2-APB, putative blockers of IP3-sensitive release of intracellular calcium stores, caused an equal and significant inhibition of 24% of the TiTX gamma-induced release of [3H]dopamine, while the slight inhibition evoked by dantrolene, a putative blocker of ryanodine-sensitive calcium store was not significant. 5. Nomifensine and ascorbic acid, blockers of dopamine transporter (DAT), caused an inhibition of 27 and 29%, respectively, on the toxin-induced release of [3H]dopamine suggesting that most of the TiTX gamma-induced release of dopamine is not due to the reversal of Na+ gradient. 6. In conclusion the majority of the TiTX gamma-induced release of [3H]dopamine is exocytotic and mobilizes calcium from the intracellular IP3-sensitive calcium stores.
authors.affiliation: Departamento de Farmacologia, Instituto de Ciências Biológicas, UFMG, 31270-901-Belo Horizonte, MG-Brasil.
authors.forename: Virginia Maria Vidigal
authors.initials: VM
authors.lastname: Fernandes
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Romano-Silva
authors.forename: Dawidson Assis
authors.initials: DA
authors.lastname: Gomes
authors.forename: Marco Antonio Máximo
authors.initials: MA
authors.lastname: Prado
authors.forename: Tasso Moraes
authors.initials: TM
authors.lastname: Santos
authors.forename: Marcus Vinicius
authors.initials: MV
authors.lastname: Gomez
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology*; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000494:pharmacology*
chemical_list: D009498:Neurotoxins; D012604:Scorpion Venoms; C119038:Ts-gamma neurotoxin; D004298:Dopamine