Effects of tetrahydroprotoberberines on dopamine D2 receptors in ventral tegmental area of rat
Abstract
AIM: To compare the actions of tetrahydroprotoberberines (THPB) on dopamine (DA)
D2 receptors in the ventral tegmental area (VTA) of rat.
METHODS: Extracellular single unit recording technique was used in i.v.
gallamine-paralyzed rats.
RESULTS: Eleven THPB analogs tested completely attenuated the apomorphine (Apo,
20 micrograms.kg-1)-induced inhibition on VTA DA cell firing activity. The OH
group on C2 at THPB was linked with the reversal of Apo-induced inhibition. Their
reversal potencies (ED50, microgram.kg-1) for D2 receptors were: THPB-143 (5.6) >
SPD (8.5) > Iso (17.0) > THP (33) > THB (48) > THPB-18 (66) > THPB-1 (179) >
THPB-19 (408) > THPB-126 (510) > THPB-104 (1019) > THPB-10 (4815).
CONCLUSION: Among these 11 THPB, the 2-hydroxyl-THPB (THPB-143) showed the
strongest antagonistic action on D2 receptors.
Keywords:
D2 receptors in the ventral tegmental area (VTA) of rat.
METHODS: Extracellular single unit recording technique was used in i.v.
gallamine-paralyzed rats.
RESULTS: Eleven THPB analogs tested completely attenuated the apomorphine (Apo,
20 micrograms.kg-1)-induced inhibition on VTA DA cell firing activity. The OH
group on C2 at THPB was linked with the reversal of Apo-induced inhibition. Their
reversal potencies (ED50, microgram.kg-1) for D2 receptors were: THPB-143 (5.6) >
SPD (8.5) > Iso (17.0) > THP (33) > THB (48) > THPB-18 (66) > THPB-1 (179) >
THPB-19 (408) > THPB-126 (510) > THPB-104 (1019) > THPB-10 (4815).
CONCLUSION: Among these 11 THPB, the 2-hydroxyl-THPB (THPB-143) showed the
strongest antagonistic action on D2 receptors.