Somatostatin and CCK-8 modulate release of striatal amino acids: role of dopamine receptors.
The effects of somatostatin (SOM) and cholecystokinin octapeptide (CCK-8) on basal and potassium-evoked release of neurotransmitter amino acids were investigated in slices of rat caudate nucleus (CN) and, for comparison, cerebral cortex (CX). Endogenous aspartate (Asp), glutamate (Glu), glycine (Gly), and gamma-aminobutyric acid (GABA) were measured by high performance liquid chromatography. In both CN and CX, potassium (5-55 mM) produced a concentration-dependent increase in the release of Asp, Glu, Gly, and GABA in the presence of extracellular Ca2+. CCK-8 (1 microM) stimulated in CN the basal and K+-evoked release of Gly to 231% and 160% of control, respectively; this effect was blocked by sulpiride (SULP), a dopamine receptor antagonist. In contrast, SOM (1 microM) inhibited the K+-evoked release of Glu in CN by 26%, an effect that was not blocked by SULP. SOM and CCK-8 did not significantly affect the basal or K+ (35 mM)-evoked release of other amino acids in the CN or of any amino acids in CX. The results indicate that: CCK-8 facilitation of Gly release is dependent of Gly release is dependent on dopamine receptor activation, whereas the inhibition by SOM of Glu release is not: and the effects of SOM and CCK-8 are specific with respect to the brain region affected.
Arnerić
S P
SP
Meeley
M P
MP
Reis
D J
DJ
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology*; D013004:Somatostatin / Q000494:pharmacology*
D000596:Amino Acids; D018377:Neurotransmitter Agents; D011954:Receptors, Dopamine; D013004:Somatostatin; D012844:Sincalide; D011188:Potassium; D002118:Calcium