Amines and other transmitter-like compounds in the bovine area postrema.

The bovine area postrema (AP) was examined for the presence of monoamines and other neuroactive substances which might act as neurotransmitters in the nucleus. High performance liquid chromatography indicated the occurrence of noradrenaline, adrenaline, dopamine and serotonin within the AP. Thin layer chromatography of dansylated derivatives of the AP revealed the presence of gamma amino butyric acid (GABA), glycine, glutamate and aspartate. Finally, direct immunofluorescence histochemistry localised substance P-like and serotonin-like immunoreactivity within neuronal fibres and varicosities in the AP and in the subjacent nucleus tractus solitarius. Dopamine-beta-hydroxylase-like immunoreactivity was found in neuronal perikarya throughout the AP, nucleus tractus solitarius and dorsal motor nucleus of the vagus. These studies provide evidence that dopamine, serotonin, noradrenaline and GABA may all act as neurotransmitters in the bovine AP.