SEROTONIN 5-HT1A RECEPTOR BINDING SITES IN THE BRAIN OF THE PIGEON (COLUMBA LIVIA)

Present knowledge about the serotonergic system in birdbrains is very limited, although the pigeon was used as an animal model in various studies focused on the behavioral effects of serotonergic transmission. In the mammalian brain the 5-HT1A receptor is the most widespread serotonin receptor type, and is involved in various functions. Less is known about the distribution of 5-HT1A receptors in the avian species. Therefore, we analyzed serotonin 5-HT1A receptor binding sites in the pigeon brain using quantitative in vitro receptor autoradiography with the selective radioligand [H-3]-8-hydroxy-2-(di-n-propylamino)tetralin ([H-3]-8-OH-DPAT). The receptor is differentially distributed throughout the pigeon brain. High levels of 5-HT1A receptors are found in the nucleus pretectalis (PT). Moderate densities were detected in the tectum, as well as in the telencephalic nidopallium and hyperpallium. Very low levels were found in the hippocampal formation, the amygdaloid complex, the basal ganglia, and several thalamic nuclei. Furthermore, local variations in 5-HT1A receptor densities support the concept of further subdivisions of the entopallium. The regional distribution patterns of 5-HT1A receptors mostly display a similar distribution as found in homologue brain structures of mammals. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.