A comparative study of the beta-adrenoceptors in higher song nuclei of birds.

摘要

The present study analyses the presence of beta-adrenoceptors in the main telencephalic song nuclei of the goldfinch and parakeet, species belonging to the two most important groups of birds that reproduce learned songs: oscine songbirds and parrots, respectively. Brains of both species sectioned at appropriate levels were used to perform autoradiographic saturation studies using [3H]CGP 12177 as a radioligand. The results show similar K(D)values for both species (0.1-0.3 nM) and striking differences in Bmax. Thus, beta-adrenoceptors are abundant in the telencephalic vocal control nuclei of the parakeet but not of the goldfinch. The predominance of the beta2 subtype in the song nuclei of both species is also confirmed. We conclude that these receptors could be involved in functions unique to the parakeet and therefore may contribute to the greater flexibility of the vocal system of this species. Our findings also support the possible involvement of beta-adrenoceptors in the evolution of the avian brain.