Modulation by fenoldopam (SKF 82526) and bromocriptine of the electrically evoked release of vasopressin from the rat neurohypophysis
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Single neurointermediate lobes were fixed by their stalks to a platinum wire electrode and incubated in Krebs-bicarbonate solution. Vasopressin release into the medium was determined by a radioimmunoassay. Vasopressin secretion was increased by electrical stimulation (15 Hz, 10 s trains with 10 s intervals for 10 min).
Fenoldopam (SKF 82526) had a dual effect on vasopressin release, 30 nM decreasing (by 30%) and 3 μM increasing (by 32%) the evoked vasopressin secretion. The facilitatory effect of fenoldopam was antagonized in a concentration-dependent manner by flupenthixol but not by sulpiride. Sulpiride (1 μM) prevented the inhibitory effect of fenoldopam (30 μM).
After pretreatment of the rats with the dopamine depleting agent, Ro4-1284 (2 mg/kg i.p. 1 h before the experiments), the evoked vasopressin release was decreased by 21% and the inhibitory effect of fenoldopam disappeared, but the facilitatory effect of fenoldopam was already seen at 30 nM. Similarly, bromocriptine (1–10 μM) decreased the evoked vasopressin release from untreated neurointermediate lobes by 30–40% but increased the vasopressin release by 30% after pretreatment with Ro4-1284.
The present findings further support the concept that vasopressin from the neurohypophysis is modulated by dopaminergic mechanisms. Facilitatory effects are mediated via D 1 and inhibition via D 2 receptors. The presence of endogenous dopamine seems to be necessary for the inhibitory effects to occur.
Key wordsDopamine D 1 receptor Dopamine D 2 receptor Neurointermediate lobe Vasopressin release
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- Ahn HS, Feldman SC, Markman MH (1979) Posterior pituitary adenylate cyclase: stimulation by dopamine and other agents. Brain Res 166:422–425Google Scholar
- Bicknell RJ, Leng G (1982) Endogenous opiates regulate oxytocin but not vasopressin secretion from the neurohypophysis. Nature 298:161–162Google Scholar
- Bowman D, Hope DB (1985) Forskolin: its effects on potassium-evoked release of vasopressin from the rat neurohypophysis. Br J Pharmacol 85:197–203Google Scholar
- Daly JW, Padgett W, Seamon KB (1982) Activation of cyclic AMP-generating systems in brain membranes and slices by the diterpene forskolin: augmentation of receptor-mediated responses. J Neurochem 38:532–544Google Scholar
- Dubocovich ML, Weiner N (1981) Modulation of the stimulation-evoked release of [3H]dopamine in the retina. J Pharmacol Exp Ther 219:701–707Google Scholar
- Dunnett CW (1964) New tables for multiple comparisons with a control. Biometrics 20:482–491Google Scholar
- Fuxe K, Fredholm BB, Agnati LF, Ögren S-O, Everitt BJ, Jonsson G, Gustafsson J-A (1978) Interaction of ergot drugs with central monoamine systems. Evidence for a high potential in the treatment of mental and neurological disorders. Pharmacology 16 (Suppl 1):99–134Google Scholar
- German DC, McMillen BA, Sanghera MK, Saffer SI, Shore PA (1981) Effects of severe dopamine depletion on dopamine neuronal impulse flow and on tyrosine hydroxylase regulation. Brain Res Bull 6:131–134Google Scholar
- Hahn RA, Wardell JR Jr, Sarau HM, Ridley PT (1982) Characterization of the peripheral and central effects of SK & F 82526, a novel dopamine receptor agonist. J Pharmacol Exp Ther 233:305–313Google Scholar
- Holzbauer M, Muscholl E, Racké K, Sharman DF (1983a) Evidence that dopamine is a neurotransmitter in the neurointermediate lobe of the hypophysis. Prog Brain Res 60:357–364Google Scholar
- Holzbauer M, Racké K, Muscholl E, Sharman DF (1983b) Dopamine release and synthesis in the neurointermediate lobe of the rat hypophysis in vitro after electrical stimulation of the pituitary stalk. Brain Res 277:47–54Google Scholar
- Holzbauer M, Racké K, Sharman DF (1983c) A comparison of the release of endogenous dopamine from the neural and the intermediate lobe of the rat hypophysis after electrical stimulation of the stalk. Med Biol 61:258–263Google Scholar
- Holzbauer M, Racké K (1985) The dopaminergic innervation of the intermediate lobe and of the neural lobe of the pituitary gland. Med Biol 63:97–116Google Scholar
- Holzbauer M, Racké K, Sharman DF (1985) Release of endogenous 5-hydroxytryptamine from the neural and the intermediate lobe of the rat pituitary gland evoked by electrical stimulation of the pituitary stalk. Neuroscience 15:723–728Google Scholar
- Husain MK, Fernando N, Shapiro M, Kagan A, Glick SM (1973) Radioimmunoassay of arginine vasopressin in human plasma. J Clin Endocrinol Metab 37:616–625Google Scholar
- Kebabian JW, Calne DB (1979) Multiple receptors for dopamine. Nature 277:93–96Google Scholar
- Knepel W, Meyer DK (1983) The effect of naloxone on vasopressin release from rat neurohypophysis incubated in vitro. J Physiol (Lond) 341:507–515Google Scholar
- Lightman SL, Iversen LL, Forsling ML (1982) Dopamine and [d-Ala2-d-Leu5]enkephalin inhibit the electrically stimulated neurohypophyseal release of vasopressin in vitro: evidence for calcium-dependent opiate action. J Neurosci 2:78–81Google Scholar
- Peroutka SJ, Snyder SH (1979) Multiple serotonin receptors: differential binding of [3H]-5-hydroxytryptamine, [3H]-lysergic acid diethylamide and [3H]-spiroperidol. Mol Pharmacol 16:687–699Google Scholar
- Pittman QJ, Lawrence D, Lederis K (1983) Presynaptic interactions in the neurohypophysis: endogenous modulators of release. Prog Brain Res 60:319–332Google Scholar
- Poulain DA, Wakerley JB (1982) Electrophysiology of hypothalamic magnocellular neurones secreting oxytocin and vasopressin. Neuroscience 7:773–808Google Scholar
- Racké K, Muscholl E (1986) Release of endogenous 3,4-dihydroxyphenylethylamine and its metabolites from the isolated neurointermediate lobe of the rat pituitary gland. Effects of electrical stimulation and of monoamine oxidase and reuptake. J Neurochem 46:745–752Google Scholar
- Racké K, Ritzel H, Trapp B, Muscholl E (1982a) Dopaminergic modulation of evoked vasopressin release from the isolated neurohypophysis of the rat. Possible involvement of endogenous opioids. Naunyn-Schmiedeberg's Arch Pharmacol 319:56–65Google Scholar
- Racké K, Rothländer M, Muscholl E (1982b) Isoprenaline and forskolin increase evoked vasopressin release from rat pituitary. Eur J Pharmacol 82:97–100Google Scholar
- Racké K, Rothländer M, Trapp B (1982c) Effects of the dopaminergic drug SKF 82526 and of forskolin on the electrically evoked vasopressin release from the isolated neurointermediate lobe. Naunyn-Schmiedeberg's Arch Pharmacol 319:R 74Google Scholar
- Racké K, Abel D, Meuresch J, Muscholl E (1985) The tuberohypophyseal dopamine system: dopaminergic modulation of vasopressin release. Characterization of release and metabolism of 3H-dopamine. JUPHAR Satellite Symposium Dopamine 84, in pressGoogle Scholar
- Seamon KB, Padgett W, Daly JM (1981) Forskolin: unique diterpene activator of adenylate cyclase in membranes and intact cells. Proc Natl Acad Sci USA 78:3363–3367Google Scholar
- Sibley DR, Stuart EL, Creese I (1982) Interactions of novel dopaminergic ligands with D-1 and D-2 dopamine receptors. Life Sci 31:637–645Google Scholar
- Starke K, Reimann W, Zumstein A, Hertting G (1978) Effect of dopamine receptor agonists and antagonists on release of dopamine in the rabbit caudate nucleus in vitro. Naunyn-Schmiedeberg's Arch Pharmacol 305:27–36Google Scholar
- Stoof JC, Kebabian JW (1981) Opposing roles for D-1 and D-2 dopamine receptors in efflux of cyclic AMP from rat neostriatum. Nature 294:366–368Google Scholar
- Tsou K, Greengard P (1982) Regulation of phosphorylation of protein I, IIIa, and IIIb in rat neurohypophysis in vitro by electrical stimulation and by neuroactive agents. Proc Natl Acad Sci USA 79:6075–6079Google Scholar
- Treiman M, Greengard P (1985) D-1 and D-2 dopaminergic receptors regulate protein phosphorylation in the rat neurohypophysis. Neuroscience 15:713–722Google Scholar
- Weinstock J, Wilson JW, Ladd DL, Brush CK, Pfeiffer FR, Kuo GY, Holden KG, Yim NCF, Hahn RA, Wardell JR Jr, Tobia AJ, Setler PE, Sarau HM, Ridley PT (1980) Separation of potent central and renal dopamine agonist activity in substituted 6-chloro-2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepines. J Med Chem 23:973–975Google Scholar