Pharmacological differences between the D-2 autoreceptor and the D-1 dopamine receptor in rabbit retina
The effect of dopamine receptor agonists and antagonists was studied on the calcium-dependent release of (/sup 3/H)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 (/sup 3/H)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 (/sup 3/H)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 (/sup 3/H)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.
- Research Organization:
- Univ. of Colorado School of Medicine, Denver
- OSTI ID:
- 5253864
- Journal Information:
- J. Pharmacol. Exp. Ther.; (United States), Vol. 3
- Country of Publication:
- United States
- Language:
- English
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550201* - Biochemistry- Tracer Techniques