Premium
Cholecystokinin Stimulates Dopamine Synthesis in Synaptosomes by a Cyclic AMP‐Dependent Mechanism
Author(s) -
Chowdhury Muhammad,
Steardo Luca,
Fillenz Marianne
Publication year - 1987
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 - 10.1111/j.1471-4159.1987.tb02914.x
Subject(s) - dopamine , cholecystokinin , chemistry , striatum , endocrinology , medicine , substantia nigra , synaptosome , tyrosine , biochemistry , biology , dopaminergic , in vitro , receptor
The effects of different fragments of cholecystokinin (CCK) on dopamine synthesis were studied in synaptosomal preparations from the striatum, substantia nigra, and frontal cortex. In striatal synaptosomes, dopamine synthesis rate measured by dopamine accumulation was 12.5% lower than that measured by 3,4‐dihydroxyphenylalanine (DOPA) accumulation; however, K + ‐accelerated synthesis was the same for both methods. Synthesis rate was independent of exogenous tyrosine levels. In the three regions studied, the combined stimulatory effects of 8‐Br‐cyclic AMP and high K + were additive. CCK‐5, CCK‐3, CCK‐27–33, and CCK‐8 (sulphated) enhanced synthesis, CCK‐5 being the most potent fragment. The nonsulphated octapeptide had no effect. In all three regions, CCK‐5 and high K + had an additive effect on dopamine synthesis; CCK‐5 and 8‐Br‐cyclic AMP together produced the same enhancement of synthesis as CCK‐5 alone. CCK‐5 produced similar dose‐dependent increases in dopamine synthesis and cyclic AMP accumulation in striatal synaptosomes, and both effects were blocked by the CCK antagonist proglumide.