Characteristics of stably expressed human dopamine D1a and D1b receptors: atypical behavior of the dopamine D1b receptor

TY - JOUR

T1 - Characteristics of stably expressed human dopamine D1a and D1b receptors: atypical behavior of the dopamine D1b receptor

AU - Pedersen, U B

AU - Norby, B

AU - Jensen, Anders A.

AU - Schiødt, M

AU - Hansen, A

AU - Suhr-Jessen, P

AU - Scheideler, M

AU - Thastrup, O

AU - Andersen, P H

PY - 1994

Y1 - 1994

N2 - Human dopamine D1a and D1b receptors were stably expressed in Baby Hamster Kidney (BHK) or Chinese Hamster Ovary (CHO) cells. [3H]SCH23390 saturation experiments indicated the presence of only a single binding site in the D1a expressing cell line with a Kd of 0.5 nM. In D1b expressing cell lines, two binding sites were observed with Kd values of 0.5 and 5 nM in CHO cells and 0.05 and 1.6 nM in BHK cells, respectively. Neither of the receptors affected Ca2+ metabolism whereas they both were coupled in a stimulatory fashion to adenylyl cyclase. The pharmacological profile of both the D1a and D1b receptors as assessed from inhibition of specific [3H]SCH 23390 binding was classical D1-like. Thus, benzazepine derivatives as well as the atypical neuroleptics, clozapine and fluperlapine, exhibited high affinity whereas D2 selective compounds like sulpiride and spiperone had low affinity for these receptors. Besides SCH 23390, only NNC 112, fluphenazine and bulbocapnine were able to discriminate between the two states of the D1b receptor. In case of the D1a receptor, the Ki values obtained in binding experiments were very similar to Ki values obtained from inhibition of dopamine stimulated adenylyl cyclase. In the D1b expressing cell line, the Ki values obtained from inhibition of the dopamine stimulated adenylyl cyclase indicated a significantly better correlation with the state of the D1b receptor showing high affinity for antagonists. In agreement with observations from binding experiments, dopamine was around 20 fold more potent in stimulating adenylyl cyclase via the D1b receptor as compared to the D1a receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

AB - Human dopamine D1a and D1b receptors were stably expressed in Baby Hamster Kidney (BHK) or Chinese Hamster Ovary (CHO) cells. [3H]SCH23390 saturation experiments indicated the presence of only a single binding site in the D1a expressing cell line with a Kd of 0.5 nM. In D1b expressing cell lines, two binding sites were observed with Kd values of 0.5 and 5 nM in CHO cells and 0.05 and 1.6 nM in BHK cells, respectively. Neither of the receptors affected Ca2+ metabolism whereas they both were coupled in a stimulatory fashion to adenylyl cyclase. The pharmacological profile of both the D1a and D1b receptors as assessed from inhibition of specific [3H]SCH 23390 binding was classical D1-like. Thus, benzazepine derivatives as well as the atypical neuroleptics, clozapine and fluperlapine, exhibited high affinity whereas D2 selective compounds like sulpiride and spiperone had low affinity for these receptors. Besides SCH 23390, only NNC 112, fluphenazine and bulbocapnine were able to discriminate between the two states of the D1b receptor. In case of the D1a receptor, the Ki values obtained in binding experiments were very similar to Ki values obtained from inhibition of dopamine stimulated adenylyl cyclase. In the D1b expressing cell line, the Ki values obtained from inhibition of the dopamine stimulated adenylyl cyclase indicated a significantly better correlation with the state of the D1b receptor showing high affinity for antagonists. In agreement with observations from binding experiments, dopamine was around 20 fold more potent in stimulating adenylyl cyclase via the D1b receptor as compared to the D1a receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

KW - Adenylate Cyclase

KW - Animals

KW - Benzazepines

KW - CHO Cells

KW - Calcium

KW - Cell Membrane

KW - Cells, Cultured

KW - Cricetinae

KW - Cyclic AMP

KW - Humans

KW - Kidney

KW - Receptors, Dopamine D1

KW - Second Messenger Systems

M3 - Journal article

C2 - 8206133

SN - 0014-2999

VL - 267

SP - 85

EP - 93

JO - European Journal of Pharmacology

JF - European Journal of Pharmacology

IS - 1

ER -