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Calbindin‐immunoreactive neurons in the reticular formation of the rat brainstem: Catecholamine content and spinal projections
Author(s) -
Goodchild Ann K.,
LlewellynSmith Ida J.,
Sun QiJian,
Chalmers John,
Cunningham Anne M.,
Pilowsky Paul M.
Publication year - 2000
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/1096-9861(20000828)424:3<547::aid-cne11>3.0.co;2-o
Subject(s) - brainstem , biology , catecholamine , reticular formation , neuroscience , reticular connective tissue , anatomy , central nervous system
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. J. Comp. Neurol. 424:547–562, 2000. © 2000 Wiley‐Liss, Inc.