Abstract
Serotonergic transmission is terminated by serotonin transporter (SERT)-mediated uptake following activation of serotonin receptors, several subtypes of which are present in the medial nucleus of the solitary tract (mNTS) at the area postrema level. In this region, serotonin (5HT) is a major modulator of the baroreceptor reflex and also affects gastric motility. This serotonin is derived from multiple sources including local neurons and inputs from raphe and visceral vagal afferents. To determine the relevant functional sites for serotonin uptake in the mNTS, we examined the electron microscopic localization of SERTs using both immunoperoxidase and immunogold labeling in rat brain. In addition, we combined these methods for dual labeling of SERTs and 5HT2A receptors to detect whether the SERT in this region was located near or at a distance from the sites of activation of these G-protein coupled receptors. Intensive SERT immunolabeling was seen on plasma membranes of axons and morphologically heterogeneous axon terminals that formed symmetric or asymmetric synapses on dendrites without detectable 5HT2A immunoreactivity (IR). 5HT2A-IR was, however, located in other nearby neuronal and glial profiles, some of which apposed intensively SERT-labeled terminals or terminals containing lower intensity of SERT immunolabeling. In somatodendritic profiles, co-expression of SERT and 5HT2A receptor immunolabeling was seen near synapses and Golgi lamellae. Our results suggest that in the mNTS 5HT activates 5HT2A receptors at a distance from SERT-mediated uptake sites in diverse cell types including some that express both 5HT2A receptors and SERTs.
Similar content being viewed by others
References
Aicher, S. A., Sharma, S. & Pickel, V. M. (1999) N-methyl-D-aspartate receptors are present in vagal afferents and their dendritic targets in the nucleus tractus solitarius. Neuroscience 91, 119–132.
Asberg, M., Eriksson, B., Martensson, B., Traskman-Bendz, L. & Wagner, A. (1986) Therapeutic effects of serotonin uptake inhibitors in depression. Journal of Clinical Psychiatry 47(Suppl.), 23–35.
Azmitia, E. & Segal, M. (1978) An autoradiographic analysis of the differential ascending projections of the dorsal and median raphe nuclei in the rat. Journal of Comparative Neurology 179, 641–667.
Balkovetz, D., Tiruppathi, C., Leibach, F., Mahesh, V. & Ganapathy, V. (1989) Evidence for an imipramine-sensitive serotonin transporter in human placental brush-border membranes. Journal of Biological Chemistry 264, 2195–2198.
Baraban, J. & Aghajanian, G. (1981) Noradrenergic innervation of serotonergic neurons in the dorsal raphe: Demonstration by electron microscopic autoradiography. Brain Research 204, 1–11.
Beaudet, A. & Descarries, L. (1978) The monoamine innervation of rat cerebral cortex: Synaptic and nonsynaptic axon terminals. Neuroscience 3, 851–860.
Beckman, M. & Quick, M. (1998) Neurotransmitter transporters: Regulators of function and functional regulation. Journal of Membrane Biology 164, 1–10.
Blakely, R. & Bauman, A. (2000) Biogenic amine transporters: Regulation in flux. Current Opinion in Neurobiology 10, 328–336.
Blakely, R., Ramamoorthy, S., Schroeter, S., Qian, Y., Apparsundaram, S., Galli, A. & de, F. L. (1998) Regulated phosphorylation and trafficking of antidepressant-sensitive serotonin transporter proteins. Biological Psychiatry 44, 169–178.
Bruns, D., Engert, F. & Lux, H. (1993) A fast activating presynaptic reuptake current during serotonergic transmission in identified neurons of Hirudo. Neuron 10, 559–572.
Bruns, D., Riedel, D., Klingauf, J. & Jahn, R. (2000) Quantal release of serotonin. Neuron 28, 205–220.
Bunin, M. & Wightman, R. (1998) Quantitative evaluation of 5-hydroxytryptamine (serotonin) neuronal release and uptake: An investigation of extrasynaptic transmission. Journal of Neuroscience 18, 4854–4860.
Cai, Y., Hay, M. & Bishop, V. (1996) Synaptic connections and interactions between area postrema and nucleus tractus solitarius. Brain Research 724, 121–124.
Calza, L., Giardino, L., Grimaldi, R., Rigoli, M., Steinbusch, H. & Tiengo, M. (1985) Presence of 5-HT-positive neurons in the medial nuclei of the solitary tract. Brain Research 347, 135–139.
Chan, J., Aoki, C. & Pickel, V. M. (1990) Optimization of differential immunogold-silver and peroxidase labeling with maintenance of ultrastructure in brain sections before plastic embedding. Journal of Neuroscience Methods 33, 113–127.
Chan-Palay, V. (1975) Fine structure of labeled axons in the cerebellar cortex and nuclei of rodents and primates after intraventricular infusions with tritiated serotonin. Anatomy and Embryology 148, 235–265.
Cinquanta, M., Ratovitski, T., Crespi, D., Gobbi, M., Mennini, T. & Simantov, R. (1997) Carriermediated serotonin release induced by d-fenfluramine: Studies with human neuroblastoma cells transfected with a rat serotonin transporter. Neuropharmacology 36, 803–809.
Cornea-Hebert, V., Riad, M., Wu, C., Singh, S. K. & Descarries, L. (1999) Cellular and subcellular distribution of the serotonin 5-HT2A receptor in the central nervous system of adult rat. Journal of Comparative Neurology 409, 187–209.
Cunningham, E., Miselis, R. & Sawchenko, P. (1994) The relationship of efferent projections from the area postrema to vagal motor and brain stem catecholamine-containing cell groups: An axonal transport and immunohistochemical study in the rat. Neuroscience 58, 635–648.
de, Chaffoy de Courcelles, D., roevens, P. & van, B. H. (1984) Stimulation by serotonin of 40 kDa and 20 kDa protein phosphorylation in human platelets. FEBS Letters 171, 289–292.
de, Potter, W., Kurzawa, R., Miserez, B. & Coen, E. (1995) Evidence against differential release of noradrenaline, neuropeptide Y, and dopamine-betahydroxylase from adrenergic nerves in the isolated perfused sheep spleen. Synapse 19, 67–76.
Deecher, D., Wilcox, B., Dave, V., Rossman, P. & Kimelberg, H. (1993) Detection of 5hydroxytryptamine2 receptors by radioligand binding, northern blot analysis, and Ca2+ responses in rat primary astrocyte cultures. Journal of Neuroscience Research 35, 246–256.
Dewar, K., Grondin, L., Carli, M., Lima, L. & Reader, T. (1992) [3H]paroxetine binding and serotonin content of rat cortical areas, hippocampus, neostriatum, ventral mesencephalic tegmentum, and midbrain raphe nuclei region following p-chlorophenylalanine and p-chloroamphetamine treatment. Journal of Neurochemistry 58, 250–257.
Eddahibi, S., Humbert, M., Fadel, E., Raffestin, B., Darmon, M., Capron, F., Simonneau, G., Dartevelle, P., Hamon, M. & Adnot, S. (2001) Serotonin transporter overexpression is responsible for pulmonary artery smooth muscle hyperplasia in primary pulmonary hypertension. Journal of Clinical Investigation 108, 1141–1150.
Eison, A., Eison, M., Torrente, J., Wright, R. & Yocca, F. (1990) Nefazodone: Preclinical pharmacology of a new antidepressant. Psychopharmacology Bulletin 26, 311–315.
Franchini, L., Johnson, A., De, O. J. & Vivas, L. (2002) Sodium appetite and Fos activation in serotonergic neurons. American Journal of Physiology Regulatory, Integrative and Comparative Physiology 282, R235–R243.
Haase, J., Killian, A., Magnani, F. & Williams, C. (2001) Regulation of the serotonin transporter by interacting proteins. Biochemical Society Transactions 29, 722–728.
Hensler, J., Ferry, R., Labow, D., Kovachich, G. & Frazer, A. (1994) Quantitative autoradiography of the serotonin transporter to assess the distribution of serotonergic projections from the dorsal raphe nucleus. Synapse 17, 1–15.
Herkenham, M. (1999) Extrasynaptic receptors and parasynaptic communication in the brain. Brain Research Bulletin 50, 351–352.
Hoffman, B., Mezey, E. & Brownstein, M. (1991) Cloning of a serotonin transporter affected by antidepressants. Science 254, 579–580.
Housley, G., Martin-Body, R., Dawson, N. & Sinclair, J. (1987) Brain stem projections of the glossopharyngeal nerve and its carotid sinus branch in the rat. Neuroscience 22, 237–250.
Hoyer, D., Hannon, J. & Martin, G. (2002) Molecular, pharmacological and functional diversity of 5HT receptors. Pharmacology Biochemistry and Behavior 71, 533–554.
Hsu, S. M., Raine, L. & Fanger, H. (1981) Use of avidin-biotin-peroxidase complex (ABC) in immunoperoxidase techniques:Acomparison between ABC and unlabeled antibody (PAP) procedures. Journal of Histochemistry and Cytochemistry 29, 577–580.
Huang, J. & Pickel, V. (2002) Differential distribution of 5HT2AandNMDAreceptors in single cells within the rat medial nucleus of the solitary tract [In Process Citation]. Synapse 44, 64–75.
Inazu, M., Takeda, H., Ikoshi, H., Sugisawa, M., Uchida, Y. & Matsumiya, T. (2001) Pharmacological characterization and visualization of the glial serotonin transporter. Neurochemistry International 39, 39–49.
Jacobs, B. & Azmitia, E. (1992) Structure and function of the brain serotonin system. Physiological Reviews 72, 165–229.
Kohler, C., Chan-Palay, V. & Steinbusch, H. (1981) The distribution and orientation of serotonin fibers in the entorhinal and other retrohippocampal areas. An immunohistochemical study with anti-serotonin antibodies in the rats brain. Anatomy and Embryology 161, 237–264.
Kuffler, D., Nicholls, J. & Drapeau, P. (1987) Transmitter localization and vesicle turnover at a serotoninergic synapse between identified leech neurons in culture. Journal of Comparative Neurology 256, 516–526.
Lebrand, C., Cases, O., Adelbrecht, C., Doye, A., Alvarez, C., El, M. S., Seif, I. & Gaspar, P. (1996) Transient uptake and storage of serotonin in developing thalamic neurons. Neuron 17, 823–835.
Lemberger, L., Fuller, R. & Zerbe, R. (1985) Use of specific serotonin uptake inhibitors as antidepressants. Clinical Neuropharmacology 8, 299–317.
Leranth, C. & Pickel, V. M. (1989) Electron microscopic pre-embedding double immunostaining methods. In Neuroanatomical Tract-tracing Methods 2: Recent Progress (edited by Heimer, L. & Zaborszky, L.) pp. 129–172. New York: Plenum Publishing Co.
Lesch, K., Wolozin, B., Murphy, D. & Reiderer, P. (1993) Primary structure of the human platelet serotonin uptake site: Identity with the brain serotonin transporter. Journal of Neurochemistry 60, 2319–2322.
Maley, B. & Elde, R. (1982) The ultrastructural localization of serotonin immunoreactivity within the nucleus of the solitary tract of the cat. Journal of Neuroscience 2, 1499–1506.
Masson, J., Sagne, C., Hamon, M. & El, M. S. (1999) Neurotransmitter transporters in the central nervous system. Pharmacological Reviews 51, 439–464.
Merahi, N., Orer, H. S. & Laguzzi, R. (1992) 5-HT2 receptors in the nucleus tractus solitarius: Characterization and role in cardiovascular regulation in the rat. Brain Research 575, 74–78.
Myers, C., Lazo, J. & Pitt, B. (1989) Translocation of protein kinase C is associated with inhibition of 5-HT uptake by cultured endothelial cells. American Journal of Physiology 257, L253–L258.
N′diaye, A., Sevoz-Couche, C., Nosjean, A., Hamon, M. & Laguzzi, R. (2001) Stimulation of 5HT2 receptors in the nucleus tractus solitarius enhances NMDA receptor-mediated reflex-evoked bradycardiac responses in the rat. Autonomic Neuroscience 92, 45–55.
Newton, B., Maley, B. & Traurig, H. (1985) The distribution of substance P, enkephalin, and serotonin immunoreactivities in the area postrema of the rat and cat. Journal of Comparative Neurology 234, 87–104.
Newton, B., Melvin, J. & Hamill, R. (1987) Central neurotoxic effects of guanethidine: Altered serotonin and enkephalin neurons within the area postrema. Brain Research 404, 151–161.
Nirenberg, M., Liu, Y., Peter, D., Edwards, R. & Pickel, V. (1995) The vesicularmonoaminetransporter 2 is present in small synaptic vesicles and preferentially localizes to large dense core vesicles in rat solitary tract nuclei. Proceedings of the National Academy of Sciences 92, 8773–8777.
Nishio, H., Nezasa, K. & Nakata, Y. (1995) Role of calcium ion in platelet serotonin uptake regulation. European Journal of Pharmacology 288, 149–155.
Nitsch, C. & Rinne, U. (1981) Large dense-core vesicle exocytosis and membrane recycling in the mossy fiber synapses of the rabbit hippocampus during epileptiform seizures. Journal of Neurocytology 10, 201–209.
Nosjean, A., Compoint, C., Buisseret-Delmas, C., Orer, H., Merahi, N., Puizillout, J. & Laguzzi, R. (1990) Serotonergic projections from the nodose ganglia to the nucleus tractus solitarius: An immunohistochemical and double labeling study in the rat. Neuroscience Letters 114, 22–26.
Persico, A., Mengual, E., Moessner, R., Hall, F., Revay, R., Sora, I., Arellano, J., De, F. J., Gimenez-Amaya, J., Conciatori, M., Marino, R., Baldi, A., Cabib, S., Pascucci, T., Uhl, G., Murphy, D., Lesch, K., Keller, F. & Hall, S. (2001) Barrel pattern formation requires serotonin uptake by thalamocortical afferents, and not vesicular monoamine release. Journal of Neuroscience 21, 6862–6873.
Peters, A., Palay, S. L. & Webster, H.D.E.F. (1991) The Fine Structure of the Nervous System.NewYork: Oxford University Press.
Pickel, V. & Chan, J. (1999) Ultrastructural localization of the serotonin transporter in limbic and motor compartments of the nucleus accumbens. Journal of Neuroscience 19, 7356–7366.
Pickel, V. M., Joh, T. H., Chan, J. & Beaudet, A. (1984) Serotoninergic terminals: Ultrastructure and synaptic interaction with catecholamine-containing neurons in the medial nuclei of the solitary tracts. Journal of Comparative Neurology 225, 291–301.
Pompeiano, M., Palacios, J. M. & Mengod, G. (1994) Distribution of the serotonin 5-HT2 receptor family mRNAs: Comparison between 5-HT2A and 5-HT2C receptors. Brain Research Molecular Brain Research 23, 163–178.
Qian, Y., Galli, A., Ramamoorthy, S., Risso, S., De, F. L. & Blakely, R. (1997) Protein kinase C activation regulates human serotonin transporters in HEK-293 cells via altered cell surface expression. Journal of Neuroscience 17, 45–57.
Qian, Y., Melikian, H., Rye, D., Levey, A. & Blakely, R. (1995) Identification and characterization of antidepressant-sensitive serotonin transporter proteins using site-specific antibodies. Journal of Neuroscience 15, 1261–1274.
Rahimian, R. & Hrdina, P. (1995) Possible role of protein kinase C in regulation of 5-hydroxytryptamine 2A receptors in rat brain. Canadian Journal of Physiological Pharmacology 73, 1686–1691.
Ramamoorthy, S., Bauman, A., Moore, K., Han, H., Yang-Feng, T., Chang, A., Ganapathy, V. & Blakely, R. (1993) Antidepressant-and cocaine-sensitive human serotonin transporter: Molecular cloning, expression, and chromosomal localization. Proceedings of the National Academy of Sciences 90, 2542–2546.
Ramamoorthy, S., Giovanetti, E., Qian, Y. & Blakely, R. (1998) Phosphorylation and regulation of antidepressant-sensitive serotonin transporters. Journal of Biological Chemistry 273, 2458–2466.
Ravary, A., Muzerelle, A., Darmon, M., Murphy, D., Moessner, R., Lesch, K. & Gaspar, P. (2001) Abnormal trafficking and subcellular localization of an N-terminally truncated serotonin transporter protein. European Journal of Neuroscience 13, 1349–1362.
Rodriguez, J., Garcia, D. & Pickel, V. (1999) Subcellular distribution of 5-hydroxytryptamine2A and Nmethyl-D-aspartate receptors within single neurons in rat motor and limbic striatum. Journal of Comparative Neurology 413, 219–231.
Rudnick, G. (1977) Active transport of 5-hydroxytryptamine by plasma membrane vesicles isolated from human blood platelets. Journal of Biological Chemistry 252, 2170–2174.
Schaffar, N., Kessler, J. P., Bosler, O. & Jean, A. (1988) Central serotonergic projections to the nucleus tractus solitarii: Evidence from a double labeling study in the rat. Neuroscience 26, 951–958.
Schmid, J., Just, H. & Sitte, H. (2001) Impact of oligomerization on the function of the human serotonin transporter. Biochemical Society Transactions 29, 732–736.
Sykes, R. M., Spyer, K. M. & Izzo, P. N. (1994) Central distribution of substance P, calcitonin gene-related peptide and 5-hydroxytryptamine in vagal sensory afferents in the rat dorsal medulla. Neuroscience 59, 195–210.
Tao-cheng, J. & Zhou, F. (1999) Differential polarization of serotonin transporters in axons versus somadendrites: An immunogold electron microscopy study. Neuroscience 94, 821–830.
Tsukamoto, K., Sved, A., Ito, S., Komatsu, K. & Kanmatsuse, K. (2000) Enhanced serotoninmediated responses in the nucleus tractus solitarius of spontaneously hypertensive rats. Brain Research 863, 1–8.
Vardhan, A., Kachroo, A. & Sapru, H. N. (1993) Excitatory amino acid receptors in commissural nucleus of the NTS mediate carotid chemoreceptor responses. American Journal of Physiology 264, R41–50.
Wade, P., Chen, J., Jaffe, B., Kassem, I., Blakely, R. & Gershon, M. (1996) Localization and function of a 5-HT transporter in crypt epithelia of the gastrointestinal tract. Journal of Neuroscience 16, 2352–2364.
Wright, D. E., Seroogy, K. B., Lundgren, K. H., Davis, B. M. & Jennes, L. (1995) Comparative localization of serotonin1A, 1C, and 2 receptor subtype mRNAs in rat brain. Journal of Comparative Neurology 351, 357–373.
Wu, C., Yoder, E. J., Shih, J., Chen, K., Dias, P., Shi, L., Ji, X. D., Wei, J., Conner, J. M., Kumar, S., Ellisman, M. H. & Singh, S. K. (1998) Development and characterization of monoclonal antibodies specific to the serotonin 5-HT2A receptor. Journal of Histochemistry and Cytochemistry 46, 811–824.
Zhou, F., Tao-Cheng, J., Segu, L., Patel, T. & Wang, Y. (1998) Serotonin transporters are located on the axons beyond the synaptic junctions: Anatomical and functional evidence. Brain Research 805, 241–254.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Huang, J., Pickel, V.M. Serotonin transporters (SERTs) within the rat nucleus of the solitary tract: Subcellular distribution and relation to 5HT2A receptors. J Neurocytol 31, 667–679 (2002). https://doi.org/10.1023/A:1025795729393
Issue Date:
DOI: https://doi.org/10.1023/A:1025795729393