Glutamate and GABA content of calbindin-immunoreactive nerve terminals in the rat intermediolateral cell column.
Immunoreactivity for calbindin-D28K (calbindin) occurs in some bulbospinal vasopressor neurons in the rostral ventrolateral medulla and calbindin-immunoreactive terminals form synapses in the intermediolateral cell column (IML), where the cell bodies of sympathetic preganglionic neurons are located. In this study, we used post-embedding immunogold labelling to determine whether calbindin terminals in the IML contained the excitatory amino acid neurotransmitter glutamate. We also assessed GABA immunoreactivity in semi-serial sections through the same terminals since this inhibitory amino acid transmitter is present in the inputs to sympathetic preganglionic neurons that lack glutamate. Analysis of 42 calbindin-positive terminals whose postsynaptic targets were not identified revealed two major groups on the basis of amino acid content. One group was immunoreactive for glutamate; and the other, for GABA. In addition, about 20% of the calbindin terminals were positive for both glutamate and GABA. Our anatomical methods cannot differentiate whether this third group is a subset of the GABAergic terminals or a separate population capable of co-releasing the two amino acids.
Llewellyn-Smith
I J
IJ
Cardiovascular Neuroscience Group, Cardiovascular Medicine and Centre for Neuroscience, Flinders University, Bedford Park, South Australia, Australia. Ida.Llewellyn-Smith@flinders.edu.au
Martin
C L
CL
Minson
J B
JB
D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000378:metabolism; D064092:Calbindin 1; D064026:Calbindins; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000378:metabolism*; D051381:Rats; D011921:Rats, Inbred WKY; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid