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.
Laboratory of Neurophysiology, Sinai Research Institute, Detroit, MI 48235.
A S
AS
Freeman
L A
LA
Chiodo
S I
SI
Lentz
K
K
Wade
M J
MJ
Bannon
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