![]() |
|
|
ML Dubocovich and N Weiner
The effect of dopamine receptor agonists and antagonists was studied on the calcium-dependent release of [3H]dopamine elicited by field stimulation at 3 Hz for a duration of 1 min (20 mA, 2 msec) from the rabbit retina in vitro and on adenylate cyclase activity in homogenates of rabbit retina. The relative order of potency of dopamine receptor agonists to inhibit the stimulation-evoked [3H]dopamine release was pergolide greater than bromocriptine greater than apomorphine greater than LY 141865 greater than N,N-di-n-propyldopamine greater than or equal to dopamine. The relative order of potencies of dopamine receptor antagonists to increase [3H]dopamine release was: S-sulpiride greater than or equal to domperidone greater than or equal to spiroperidol greater than metoclopramide greater than fluphenazine greater than or equal to R-sulpiride. alpha-Flupenthixol (0.01-1 microM) and (+)- butaclamol (0.01-1 microM) did not increase [3H]dopamine overflow when added alone, but they antagonized the concentration-dependent inhibitory effect of apomorphine (0.1-10 microM). These results suggest that the dopamine inhibitory autoreceptor involved in the modulation of dopamine release from the rabbit retina possesses the pharmacological characteristics of a D-2 dopamine receptor. Maximal stimulation by 30 microM dopamine resulted in a 3-fold increase in adenylate cyclase activity with half-maximal stimulation occurring at a concentration of 2.46 microM. Apomorphine and pergolide elicited a partial stimulation of adenylate cyclase activity. However, at low concentrations both compounds were more potent than dopamine. N,N-di-n-Propyl-dopamine was 30 times less potent than dopamine, and bromocriptine was unable to stimulate adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
This article has been cited by other articles:
![]() |
C. O. Jaliffa, F. F. Lacoste, D. W. Llomovatte, M. I. K. Sarmiento, and R. E. Rosenstein Dopamine Decreases Melatonin Content in Golden Hamster Retina J. Pharmacol. Exp. Ther., April 1, 2000; 293(1): 91 - 95. [Abstract] [Full Text] |
||||
![]() |
Y. Wang, K. Harsanyi, and S. C. Mangel Endogenous Activation of Dopamine D2 Receptors Regulates Dopamine Release in the Fish Retina J Neurophysiol, July 1, 1997; 78(1): 439 - 449. [Abstract] [Full Text] [PDF] |
||||