Summary
The cardiovascular effects of selective alpha1 and alpha2 agonists and antagonists injected into the nucleus tractus solitarii (NTS) were studied in urethane-anesthetized rats. Methoxamine (0.3–3 μg) injected bilaterally into the NTS caused a dose-dependent increase in blood pressure and heart rate. Phenylephrine (6 μg) and an imidazolidine derivative St 587 (3 μg) similarly injected also produced an increase in blood pressure, whereas a-methylnoradrenaline and an azepine derivative B-HT 920 (1 and 3 μg) caused a decrease in blood pressure and heart rate. The pressor response to methoxamine (1 μg) was markedly inhibited by prazosin (0.3 pg) injected into the same sites or hexamethionum (25 mg/kg, i. v.). Prazosin (0.3 μg) alone injected bilaterally into the NTS did not affect the blood pressure, while yohimbine (0.1 μg) similarly injected increased the pressure. These results suggest that in the rat NTS there exist alpha1 adrenoceptors responsible for an increase in arterial pressure. The NTS alpha2 adrenoceptors seem to be involved in the tonic regulation of arterial pressure.
Similar content being viewed by others
References
Andén N-E, Gomes C., Persson B, Trolin G (1978) R28935 and prazosin: effects on central and peripheral alpha-adrenoceptor activity and on blood pressure. Naunyn-Schmiedeberg's Arch Pharmacol 302:299–306
Berthelsen S, Pettinger WA (1977) A functional basis for classification of α-adrenergic receptors. Life Sci 21:595–606
Bhargava KP, Mishra N, Tangri KK (1972) An analysis of central adrenoceptors for control of cardiovascular function. Br J Pharmacol 45:596–602
Dahlström A, Fuxe K (1964) Evidence for the existence of monoamine-containing neurons in the central nervous system. I. Demonstration of monoamines in the cell bodies of brainstem neurons. Acat Physiol Scand (Suppl) 232:1–55
De Jong W (1974) Noradrenaline; central inhibitory control of blood pressure and heart rate. Eur J Pharmacol 29:179–181
De Jong W, Nijkamp FP (1976) Centrally induced hypotension and bradycardia after administration of α-methylnoradrenaline into the area of the nucleus tractus solitarii of the rat. Br J Pharmacol 58:593–598
De Jong W, Petty M (1982) Chemical stimulation of the nucleus of the solitary tract and the resulting blood pressure response. J Cardiovascular Pharmacol 4: s77-s80
De Jonge A, Van Meel JCA, Timmermanns PBMWM, Van Zwieten PA (1981) A lipophilic, selective α1-adrenoceptor agonist: 2-(2-chloro-5-trifluoromethylphenytimino) imidazolidine (St 587). Life Sci 28:2009–2016
Huchet A-M, Chelly J, Schmitt H (1981) Role of α1- and α2-adrenoceptors in the modulation of the baroreflex vagal bradycardia. Eur J Pharmacol 71:455–461
Huchet A-M, Doursout M-F, Ostermann G, Chelly J, Schmitt H (1983a) Possible role of α1- and α2-adrenoceptors in the modulation of the sympathetic component of the baroflex. Neuropharmacology 22:1243–1248
Huchet A-M, Huguet F, Ostermann G, Bakri-Logeais F, Schmitt H, Narcisse G (1983b) Central α1-adrenoceptors and cardiovascular control in normotensive and spontaneously hypertensive rats. Eur J Pharmacol 95:207–213
Kim YI, Paik YH, Kang SS, Kim JH (1982) Effects of α-adrenoceptor antagonists administered intraventricularly on central hypotensive action of clonidine and on central hypertensive action of methoxamine in rabbits. Arch Int Pharmacodyn 257:66–76
Kobinger W, Pichler L (1980) Relation between central sympathoinhibitory and peripheral pre- and postsynaptic α-adrenoceptors as evaluated by different clonidine-like substances in rats. Naunyn-Schmiedeberg's Arch Pharmacol 315:21–27
Kubo T, Hashimoto M (1978) Effects of intraventricular and intraspinal 6-hydroxydopamine on blood pressure of spontaneously hypertensive rats. Arch Int Pharmacodyn 232:166–176
Kubo T, Misu Y (1981) Pharmacological characterisation of the α-adrenoceptors responsible for a decrease of blood pressure in the nucleus tractus solitarii of the rat. Naunyn-Schmiedeberg's Arch Pharmacol 317:120–125
McCall RB, Humphrey SJ (1981) Evidence for a central depressor action of postsynaptic α1-adrenergic receptor antagonists. J Autonomic Nervous System 3:9–23
Palkovits M, Jacobowitz DM (1974) Topographic atlas of catecholamine and acetylcholinesterase-containing neurons in the rat brain. II. Hindbrain (mesencephalon, rhombencephalon). J Comp Neurol 157:29–42
Rockhold RW, Caldwell RW (1980) Cardiovascular effects following clonidine microinjection into the nucleus tractus solitarii of the rat. Neuropharmacology 19:919–922
Sinha JN, Sharma DK, Gurtu S, Pant KK, Bhargava KP (1984) Nucleus locus coeruleus: evidence for α1-adrenoceptor mediated hypotension in the cat. Naunyn-Schmiedeberg's Arch Pharmacol 326:193–197
Smith W, Egle JL, Jr., Adams MD (1982) Adrenergic receptors in the nucleus tractus solitarii of the rat. Eur J Pharmacol 81:11–19
Struyker-Boudier H, Smeets G, Brouwer G, Van Rossum JM (1975) Central nervous system a-adrenergic mechanisms and cardiovascular regulation in rats. Arch Int Pharmacodyn 213:285–293
Talman WT, Perrone MH, Reis DJ (1981) Acute hypertension after the local injection of kainic acid into the nucleus tractus solitarii of rats. Circ Res 48:292–298
Unnerstall JM, Kopajtic TA, Kuhar MJ (1984) Distributions 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
Young WS III, Kuhar MJ (1979) Noradrenergic al and α2 receptors: autoradiographic visualization. Eur J Pharmacol 59:317–319
Zandberg D, De Jong W, De Wied D (1979) Effect of catecholamine-receptor stimulating agents on blood pressure after local application in the nucleus tractus solitarii of the medulla oblongata. Eur J Pharmacol 55:43–56
Author information
Authors and Affiliations
Additional information
Send offprint requests to T. Kubo at the above address
Rights and permissions
About this article
Cite this article
Kubo, T., Kihara, M., Hata, H. et al. Cardiovascular effects in rats of alpha1 and alpha2 adrenergic agents injected into the nucleus tractus solitarii. Naunyn-Schmiedeberg's Arch Pharmacol 335, 274–277 (1987). https://doi.org/10.1007/BF00172796
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00172796