Fiszman ML, Luchelli-Fortis MA, Stefano FJ. Amphetamine antagonizes the presynaptic inhibitory effect of clonidine through an interaction at the level of the alpha 2-adrenoceptors.
GENERAL PHARMACOLOGY 1989;
20:351-8. [PMID:
2545511 DOI:
10.1016/0306-3623(89)90272-3]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. In the whole rat vas deferens 20 microM noradrenaline (NA) and 0.011 microM clonidine decreased (36 +/- 7.4% and 80 +/- 6.0% respectively) the motor response induced by hypogastric nerve stimulation. These effects were reverted by 1 microM yohimbine. Amphetamine 5.4 microM failed to antagonize the inhibitory effect of NA and attenuated clonidine effect. 2. The effect of amphetamine was not altered by preincubation with either cocaine 1 microM, (-)-propranolol 0.3 microM or cocaine plus prazosin 0.028 microM. 3. In reserpine pretreated animals amphetamine 5.4 microM shifted to the right the concentration-response curve (CRC) to clonidine 0.62 +/- 0.05 log units with a KB value of 1.83 +/- 0.30 microM. 4. Binding of [3H]clonidine and [3H]prazosin were inhibited by amphetamine. Amphetamine was 90 times more potent to inhibit [3H]clonidine binding. 5. The results obtained suggest a possible direct interaction between clonidine and amphetamine on alpha-adrenoceptor.
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