Release of cholecystokinin from rat midbrain slices and modulatory effect of D2DA receptor stimulation.
Cholecystokinin octapeptide (CCK-8) is colocalized within a majority of dopamine (DA)-containing neurons of the rat midbrain. Exogenous CCK-8 can modulate the electrophysiological activity of DA neurons, at least in part, by direct actions on the somatodendritic region of these cells. If CCK-8 is somatodendritically released from DA neurons, it may influence DA cell function as has been shown for DA itself. In the present study, radioimmunoassay was used to determine if CCK-8 is released in vitro from slices of rat midbrain under basal and depolarizing (30 mM potassium) conditions. Low levels of CCK-8 were detected in the basal incubation medium. Thirty mM potassium caused about a 3-fold increase in the release of CCK-8. This stimulated release was abolished in calcium-free medium. The D2 receptor agonist quinpirole, but not the D1 agonist SKF 38393, attenuated the potassium-stimulated release of CCK-8 but did not affect basal release. These results show that CCK-8, like DA, can be released from midbrain slices, presumably from DA/CCK-8-containing neurons. This finding is in accordance with the possibility that CCK-8 plays a role in the regulation of DA neuronal function at the level of the cell body, where it might influence the excitability of the DA cell membrane.
Freeman
A S
AS
Laboratory of Neurophysiology, Sinai Research Institute, Detroit, MI 48235.
Chiodo
L A
LA
Lentz
S I
SI
Wade
K
K
Bannon
M J
MJ
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D002766:Cholecystokinin / Q000276:immunology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D015259:Dopamine Agents / Q000494:pharmacology; D004873:Ergolines / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D008636:Mesencephalon / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D019257:Quinpirole; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism*; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D013469:Sulpiride / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D015259:Dopamine Agents; D004873:Ergolines; D007457:Iodine Radioisotopes; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D014701:Veratridine; D013469:Sulpiride; D002766:Cholecystokinin; D011188:Potassium