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In Vivo Microdialysis Evidence for Transient Dopamine Release by Benzazepines in Rat Striatum
Author(s) -
Tomiyama Katsunori,
Koshikawa Noriaki,
Funada Kunie,
Oka Koichi,
Kobayashi Masafumi
Publication year - 1995
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1995.65062790.x
Subject(s) - microdialysis , chemistry , agonist , pharmacology , dopamine , striatum , quinpirole , nomifensine , amphetamine , receptor , endocrinology , dopaminergic , extracellular , biology , biochemistry
The effects of benzazepine derivatives on extracellular levels of dopamine (DA) and l ‐3,4‐dihydroxyphenylacetic acid (DOPAC) in the dorsal striatum of freely moving rats were studied using in vivo microdialysis. Direct injection of SKF‐38393 (0.5 or 1.5 µg/0.5 µl), a selective D 1 receptor agonist, into the striatum through a cannula secured alongside a microdialysis probe produced a rapid dose‐dependent transient increase in striatal DA efflux and a more gradual reduction in efflux of DOPAC. The rapid increase in DA efflux was not affected by infusion of tetrodotoxin (TTX; 2 µ M ) or Ca 2+ ‐free Ringer's solution and occurred after either enantiomer of SKF‐38393. A TTX‐insensitive increase in DA level similar to that induced by SKF‐38393 was also seen after other benzazepines acting as agonists (SKF‐75670 and SKF‐82958, each 1.5 µg in 0.5 µl) and antagonists (SCH‐23390, 1.5 µg in 0.5 µl) at the D 1 receptor and after (+)‐amphetamine. These effects were inhibited by infusion of nomifensine (100 µ M ). It is concluded that the transient increases in striatal DA efflux seen after intrastriatal injection of SKF‐38393 and other benzazepines are not mediated by presynaptic D 1 receptors but by an amphetamine‐like action on the dopamine transporter.