Changes of [3H]spiroperidol binding in the renal artery of aged rabbits.
ABSTRACT Using mature (12 months), old (70 months) rabbits and 3H-labeled spiroperidol, the characteristics of renal artery dopamine receptors were studied. In old age the dissociation constant of [3H]spiroperidol was unchanged, while maximum specific binding was reduced more than 45%. The present data seem to indicate an impairment of peripheral dopaminergic function in ageing.
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ABSTRACT: Studies were performed on isolated pulmonary arterial segments to investigate dopamine receptor-mediated relaxant effects at different times during development. Dopamine receptor-mediated relaxant effects can only be observed when vessels are precontracted with prostaglandin F2 alpha and in the presence of alpha 1, alpha 2, beta, and serotonergic blockade. Helical strips of pulmonary arteries from rabbits of different ages (2, 7, 14, 30, and 90 days), partially precontracted by prostaglandin F2 alpha were tested for their responses to dopamine in the presence of prazosin (10(-6) M), yohimbine (10(-6) M), propranolol (10(-6) M), and methysergide (10(-6) M). Strips from 2- and 7-day-old rabbits were not induced to relax by dopamine, whereas those from 14-, 30-, and 90-day-old animals, after cumulative application of dopamine, underwent concentration-dependent relaxation. Dopamine (half the maximum response) concentration decreased during the development of rabbits from 14 to 90 days old. Mean values for apparent dopamine ED50 (half the maximum response) concentrations in the arteries of 14-, 30-, and 90-day old animals were 4.94 +/- 0.40, 2.02 +/- 0.30, and 0.113 +/- 0.028 microM, respectively. The effects of various dopamine antagonists on dopamine-induced relaxation were not markedly different at different ages. These findings indicate that dopamine receptor function is not fully developed in the pulmonary arteries of newborn rabbits, but matures as the age of the rabbit increases.Pediatric Research 09/1988; 24(2):160-5. DOI:10.1203/00006450-198808000-00004 · 2.84 Impact Factor
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ABSTRACT: 1. The pharmacological characteristics and the anatomical localization of dopamine (DA) DA-1 and DA-2 receptor sites were analysed in sections of rat heart, kidney, cerebral, mesenteric and caudal arteries. Moreover, DA-1 receptors were characterized in sections of human kidney. 2. [3H]-SCH 23390, used as a ligand of DA-1 receptors, was specifically bound to sections of cerebral and mesenteric arteries and to both rat and human kidney. Negligible amounts of specific binding were noticeable in the heart and in the caudal artery. The binding was consistent with the labelling of DA-1 sites. In rat tissues binding was not sensitive to 6-hydroxydopamine (6-OHDA) sympathectomy. 3. Anatomically [3H]-SCH 23390 was bound by the medial layer of cerebral, mesenteric and renal arteries. In the renal cortex, where occurred the highest accumulation of [3H]-SCH 23390 binding sites, the ligand was bound primarily by proximal convoluted cortical tubules and juxtaglomerular cells. Comparatively, the human kidney was richer in tubular binding sites than the rat kidney. The opposite is true for vascular sites. 4. [3H]-spiroperidol was used as a ligand of DA-2 receptors. To the incubation medium containing the ligand, appropriate concentrations of ketanserin were added to block the possible binding to 5-HT-2 sites. [3H]-spiroperidol was bound by sections of the structures examined in a manner consistent with the labelling of DA-2 sites. 6-OHDA caused a significant reduction in the density of cardiac and vascular [3H]-spiroperidol binding sites. 5. In the heart [3H]-spiroperidol was bound primarily by atria (6-OHDA sensitive binding).(ABSTRACT TRUNCATED AT 250 WORDS)Journal of Autonomic Pharmacology 02/1990; 10 Suppl 1:s11-8. DOI:10.1111/j.1474-8673.1990.tb00222.x
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ABSTRACT: 1. The kidney contains rather large stores of dopamine (DA) (both neuronal and non-neuronal) and is rich in DA-1 and DA-2 receptors. However, no information is so far available as to the age-related changes of the renal dopaminergic system. 2. DA-1 receptors were studied in the kidney of young (3-month-old), adult (12-month-old) and aged (27-month-old) male Wistar rats using radioreceptor binding and autoradiographic techniques. [3H]-SCH 23390 was used as a ligand. 3. Binding studies demonstrated a significant loss in the density but not in the affinity of [3H]-SCH 23390 binding in sections of kidney of adult animals in comparison with young animals. A further decrease in the density of DA-1 binding sites was noticeable in aged rats in comparison with adult rats. 4. Autoradiography revealed that in the kidney [3H]-SCH 23390 binding sites are located primarily within the proximal cortical tubules and, in lesser amount, within the distal cortical tubules and the smooth muscle of the intrarenal arteries. Ageing is accompanied by a more remarkable loss of tubular than vascular DA-1 receptors. 5. These findings suggest that the renal DA-1 receptor system is impaired with age similarly as described for the striatal D-1 receptor system.Journal of Autonomic Pharmacology 02/1990; 10 Suppl 1:s19-24. DOI:10.1111/j.1474-8673.1990.tb00223.x