Differential distribution of AMPA-selective glutamate receptor subunits in the parabrachial nucleus of the rat.

The parabrachial complex is made up of at least 11 cytoarchitectonically distinct subnuclei which differ in their anatomical connections and neurotransmitter content, as well as the functions they subserve. To determine whether parabrachial subnuclei also express different types of glutamate receptors, we undertook a light microscopic examination of the regional distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor subunits within the parabrachial complex using antibodies directed against synthetic peptides corresponding to the C-terminal parts of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor subunits. Antibodies that recognize GluR1 subunits stained cells mainly in the central lateral parabrachial subnucleus, whereas GluR4 antibodies selectively stained cells in the internal lateral subnucleus. In contrast, antibodies directed against the GLuR2/3 subunits stained neurons in every parabrachial subnucleus, although the most dense labelling was seen in the external lateral cell group. These differences in expression of alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionate receptor subtypes may eventually allow selective activation or inhibition of specific subsets of neurons in the parabrachial complex.