Pj. Larsen et N. Vrang, NEURONS PROJECTING TO THE HYPOTHALAMUS FROM THE BRAIN-STEM A1-CATECHOLAMINERGIC CELL GROUP EXPRESS GLUTAMATE R2,3-RECEPTOR IMMUNOREACTIVITY, Brain research, 705(1-2), 1995, pp. 209-215
Stimulation of ascending catecholaminergic neurones of the Al region i
n ventrolateral medulla by excitatory amino acids mediate neurohypophy
sial vasopressin secretion triggered by hypovolemic hypotension. Recen
t cloning of the ionotrophic excitatory amino acid receptors of the al
pha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type an
d subsequent production of receptor recognizing antisera have made imm
unocytochemical detection of receptor proteins in phenotypically chara
cterized neurones possible. Using single immunocytochemical detection
of glutamate GluR1, GluR2,3, GluR4 receptor proteins we have investiga
ted the distribution of GluR-receptor proteins in the caudal ventrolat
eral medulla. In the neurones of the Al cell group, only GluR2,3-immun
oreactivity was expressed whereas GluR1-immunoreactive neurones were s
een in the adjacent reticular formation. Using dual immunocytochemistr
y in combination with retrograde Fluorogold tracing we determined the
extent of co-expression of tyrosine-hydroxylase and glutamate GluR2,3
receptor protein immunoreactivity in neurones of the Al cell group in
the ventrolateral medulla that project to the area of the paraventricu
lar nucleus of the hypothalamus. It was seen that the majority of cate
cholaminergic Al neurones of the caudal VLM that project directly to t
he paraventricular nucleus are also immunoreactive to the Glu R2,3 rec
eptor protein further substantiating that these neurones are directly
influenced by the excitatory amino acid glutamate.