Summary
Electron-microscopic autoradiography of rat neurohypophyses treated with [3H] clonidine, an α2-agonist, showed that binding apparently occurred preferentially at the neurosecretory endings and blood vessels rather than on the pituicytes. Since it is known that clonidine has a high affinity for plasma proteins, the distribution over the neurosecretory nerve endings would suggest the existence of presynaptic α2-binding sites on neurosecretory neurones, which could indicate a regulatory function for catecholamines in neurohypophysial hormone release.
This is a preview of subscription content, log in via an institution to check access.
References
Blackett NM, Parry DM (1973) A new method for analyzing electron microscopic autoradiographs using hypothetical grain distribution. J Cell Biol 57:9–15
Blackett NM, Parry DM (1977) A simplified method of ‘hypothetical grain’ analysis of electron microscope autoradiographs. J Histochem Cytochem 25:206–214
Chrysant SG, Lavender AR (1973) Water diuresis from clonidine, an antihypertensive. Clin Res 21:410
Docherty JR, MacDonald A, McGrath JC (1979) Further subclassification of alpha adrenoceptors in the cardio-vascular system, vas deferns and anococcygeus muscle of the rat. Br J Pharmacol 67:421–422p
Hoefke W (1980) Clonidine: In: A. Scriabine (ed) Pharmacology of antihypertensive drugs. Raven Press, N.Y. 55–78
Hoefke W, Kobinger W (1966) Pharmakologische Wirkung des 2-(2,6-Dichloro-phenylamino)-2-imidazolin Hydrochlorids, einer neuen antihypertensiven Substanz. Arzneimittelforsch 16:1038–1050
Kimura T, Share L, Wang BC, Croften JT (1981) The role of central adrenoceptors in the control of vasopressin release and blood pressure. Endocrinology 108:1829–1836
Langer SZ (1974) Presynaptic regulation of catecholamine release. Biochem Pharmacol 23:1793–1800
Morris B, Livingston A (1984a) Binding of 3H clonidine to membranes from cow neurohypophysis and rat cerebral cortex. Neuropharmacology 23:1279–1283
Morris B, Livingston A (1984b) Autoradiographic demonstration of adrenoceptors in the bovine neurohypophysis. Cell Tissue Res 237:387–389
Reid IA, MacDonald DM, Pachnis B, Ganong WF (1975) Studies concerning the mechanism of suppression of renin secretion by clonidine. J Pharmacol Exp Ther 192:713–721
Reid IA, Nolan PL, Wolf JA, Keil LC (1979) Suppression of vasopressin secretion by clonidine: Effect of adrenoceptor antagonists. Endocrinology 104:1403–1406
Unnerstall JR, Kopajtic TA, Kuhar MJ (1984) Distribution of α2-agonist binding sites in the rat and human central nervous system: analysis of some functional, anatomic correlates of the pharmacologic effects of clonidine and related adrenergic agents. Brain Res Rev 7:69–101
U'Prichard DC, Bechtel WD, Rouot BM, Snyder SH (1979) Multiple apparent alpha noradrenergic receptor binding sites in rat brain: Effect of 6-hydroxydopamine. Mol Pharmacol 16:47–60
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Livingston, A., Morris, B. Localisation of [3H] clonidine binding in rat neurohypophysis by means of electron-microscopic autoradiography. Cell Tissue Res. 244, 467–469 (1986). https://doi.org/10.1007/BF00219223
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00219223