title: Calbindin-immunoreactive neurons in the reticular formation of the rat brainstem: catecholamine content and spinal projections.
abstract: Calbindin-D28k (calbindin) is a calcium-binding protein that is distributed widely in the rat brain. The localisation of calbindin immunoreactivity in the medulla oblongata and its colocalisation with adrenaline-synthesising neurons [phenylethanolamine-N-methyltransferase-immunoreactive (PNMT-IR)] was examined (Granata and Chang [1994] Brain Res. 645:265-277). However, detailed information about the distribution of calbindin-IR neurons in the reticular formation of the medulla oblongata in particular is lacking. In this report, the authors address this issue with an emphasis on the quantitation of calbindin-IR neurons, catecholamine neurons [tyrosine hydroxylase (TH)-IR, or PNMT-IR], and spinally projecting neurons in the ventral brainstem. Rats received injections of the retrograde tracing agent cholera toxin B (CTB) into the thoracic spinal cord or into the superior cervical ganglion. Immunocytochemistry was used to reveal calbindin, TH, PNMT, and CTB immunoreactivity. Ten calbindin-IR cell groups were identified within the pontomedullary reticular formation. Seven previously undescribed but distinct clusters of calbindin-IR neurons were found. Within the ventral pons, a population of calbindin-IR neurons occurred dorsal but adjacent to the A5 cell group. These calbindin-IR neurons did not contain either TH or PNMT immunoreactivity, and few if any of these neurons projected to the spinal cord. A distinct group of calbindin-IR neurons was present in the ventral medulla. Seventy-five percent of these calbindin-IR neurons contained TH immunoreactivity, 45% contained PNMT immunoreactivity, and 21% were spinally projecting neurons. Spinally projecting, calbindin-IR neurons were a subpopulation of PNMT-IR cells. In the caudal ventral medulla, no TH-IR or PNMT-IR cells were calbindin-IR. In the intermediolateral cell column, close appositions of calbindin-IR terminals on identified sympathetic preganglionic neurons as well as calbindin-IR synapses indicated that these neurons may affect directly the sympathetic outflow. The results demonstrate for the first time the existence of a new subpopulation of spinally projecting, PNMT-IR neurons in the rostral ventrolateral medulla.
authors.affiliation: Hypertension and Stroke Research Laboratories, Department of Physiology, and Department of Neurosurgery, University of Sydney, Royal North Shore Hospital, St. Leonards, Sydney 2065, Australia.
authors.forename: A K
authors.initials: AK
authors.lastname: Goodchild
authors.forename: I J
authors.initials: IJ
authors.lastname: Llewellyn-Smith
authors.forename: Q J
authors.initials: QJ
authors.lastname: Sun
authors.forename: J
authors.initials: J
authors.lastname: Chalmers
authors.forename: A M
authors.initials: AM
authors.lastname: Cunningham
authors.forename: P M
authors.initials: PM
authors.lastname: Pilowsky
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000378:metabolism* / Q000648:ultrastructure; D064092:Calbindin 1; D064026:Calbindins; D002395:Catecholamines / Q000378:metabolism*; D004525:Efferent Pathways / Q000378:metabolism* / Q000648:ultrastructure; D004837:Epinephrine / Q000378:metabolism; D008526:Medulla Oblongata / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D010625:Phenylethanolamine N-Methyltransferase / Q000378:metabolism; D011149:Pons / Q000378:metabolism / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats / Q000033:anatomy & histology / Q000378:metabolism*; D017208:Rats, Wistar; D012154:Reticular Formation / Q000378:metabolism* / Q000648:ultrastructure; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism* / Q000648:ultrastructure; D013564:Sympathetic Nervous System / Q000378:metabolism / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D002395:Catecholamines; D064030:S100 Calcium Binding Protein G; D014446:Tyrosine 3-Monooxygenase; D010625:Phenylethanolamine N-Methyltransferase; D004837:Epinephrine