Antiserum raised against residues 159-168 of the guanine nucleotide-binding protein G(i3)-α reacts with ependymal cells and some neurons in the rat brain containing cholecystokinin- or cholecystokinin- and tyrosine 3-hydroxylase-like immunoreactivities

Antibodies raised against a synthetic decapeptide corresponding to a specific sequence of G(i3)-α protein (an inhibitory guanine nucleotide-binding protein) were used to analyze G(i3)-α-like immunoreactivity in brain sections from colchicine-treated rats by indirect immunofluorescence histochemistry. G(i3)-α-peptide-positive cell bodies were found in the ventral tegmental area and substantia nigra, and these cells were also cholecystokinin (CCK)- and tyrosine 3-hydroxylase-positive. G(i3)-α-peptide staining was observed in perikarya in the hippocampus and in fibers in the nucleus accumbens, tuberculum olfactorium, bed nucleus of stria terminalis, and a spino-thalamic tract, where it coexisted with CCK-like immunoreactivity as well. No coexistence with CCK occurred in C(i3)-α-peptide-positive ependymal cells outlining the aqueduct and ventricles. Preadsorption of G(i3)-α antibodies with CCK-8 or CCK-33 did not alter G(i3)-α-peptide staining. The occurrence of G(i3)-α-peptide-like immunoreactivity in CCK-containing neurons may indicate the presence of G(i3)-α protein and in CCK/dopamine neurons may indicate an association of this G(i) protein with dopamine autoreceptors.