PRESENCE OF A NON-NMDA GLUTAMATE-RECEPTOR SUBTYPE IN THE SYMPATHETIC NERVOUS-SYSTEM OF NEONATAL SWINE

For the first time, the GluR-1 subtype of AMPA receptor was identified in the sympathetic nervous system of neonatal swine, an animal model of human development and heart disease. The rationale was to seek evid ence of a role ascribed to glutamate in cardiorespiratory regulation i n the laboratory rat. The receptor was demonstrated with the avidin-bi otin immunoperoxidase technique by using an affinity-purified polyclon al antibody judged to be specific to Glu-R1 in several species. Glu-R1 immunoreactivity was regionally distributed in the thoracic spinal gr ay, and present intracellularly in neurons and within the surrounding neuropil. Sympathetic preganglionic neurons in the intermediolateral c ell column of upper and lower thoracic spinal segments were intensely labeled and surrounded by labeled neuropil. High concentrations of Glu -R1 distinguished laminae II: substantia gelatinosa and the outer regi on of lamina III. Laminae I and V of the dorsal horn but not IV contai ned immunolabeled neurons. Arrays of moderately immunoreactive perikar ya extended from an intermediate zone of laminae VII to the central gr ay. Glia and perivascular processes were not labeled, confirming previ ous observations [Tachibana, M., Wenthold, R.J., Morioka, H., Petralia , R.S., 1994. Light and electron microscopic immunocytochemical locali zation of AMPA-selective glutamate receptors in the rat spinal cord. J . Comp. Neurol. 344, 431-454]. Neuronal staining patterns corroborated evidence in rats indicating a postsynaptic localization of Glu-R1 ass ociated with plasma membranes and cytoplasmic organelles [Martin, L.J. , Blackstone, C.D., Levey, A.I., Huganir, R.L., Price, D.L., 1993. AMP A glutamate receptor subunits are differentially distributed in rat br ain. Neuroscience 53, 327-358., Rubio, M.E., Wenthold, R.J., 1997. Glu tamate receptors are selectively targeted to postsynaptic sites in neu rons. Neuron 18, 939-950]. Our data predict a role for L-glutamate in postnatal development of cardiorespiratory reflexes in swine. (C) 1998 Elsevier Science B.V. All rights reserved.