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.

Central Command Regulation of Circulatory Function Mediated by Descending Pontine Cholinergic Inputs to Sympathoexcitatory Rostral Ventrolateral Medulla Neurons

“…As described previously, 29,30 injections of cholera toxin B subunit (CTB) (1%, retrograde tracer) were made centered in the intermediolateral cell column (nϭ10) or RVLM (nϭ3) under anesthesia and animals were recovered for 36 to 72 hours. Rats were transcardially perfused and brains processed for light and fluorescence immunohistochemistry 30,31 or combined in situ hybridization and immunohistochemistry as described previously.…”

“…Rats were transcardially perfused and brains processed for light and fluorescence immunohistochemistry 30,31 or combined in situ hybridization and immunohistochemistry as described previously. 32 Briefly, 50-m sections were incubated with species-specific primary antibodies to detect CTB (goat; List OR rabbit; Virostat), vesicular acetylcholine transporter (vAChT) (Chemicon), tyrosine hydroxylase (TH) (Sigma, Australia), or neuron-specific nuclear protein (NeuN) (Chemicon).…”

“…For light microscopy, vAChT and CTB were detected using enhanced diaminobenzidine reactions (nickel and imidazole). 30 …”

Characterisation of transverse slice culture preparations of postnatal rat spinal cord: preservation of defined neuronal populations

“…(c) Calbindin (CB), together with calretinin and parvalbumin, is a member of the family of calciumbinding proteins (CaBPs). CaBPs contribute to calcium homeostasis through their capacity to buffer cytosolic Ca ++ and may also play a neuroprotective role when potentially dangerous increases in intracellular calcium concentration occur (Goodchild et al 2000;Li et al 1999;Magnusson et al 1996;Ren et al 1994). CaBPs often serve as a useful molecular marker for certain types of neurons, as each of them has been observed in different subsets of neurons (Celio 1990;Li et al 2000).…”

Catecholamine-Related Gene Expression Correlates With Blood Pressures in SHR

“…In the ventrolateral medulla oblongata there are 2 populations of catecholaminergic neurons, the C1 group and the A1 group, that play key roles in arterial pressure regulation. 3 Rostral C1 neurons project directly to sympathetic preganglionic neurons in the spinal cord, providing a major sympathetic drive to regulate blood pressure, whereas the caudal C1 cells innervate neurons in the hypothalamus and forebrain. 4 A1 neurons provide an important excitatory drive to the vasopressin-releasing neurons of the hypothalamus.…”