A dorsomedial subdivision within the nucleus intercollicularis identified in the Japanese quail (Coturnix coturnix japonica) by means of alpha 2-adrenergic receptor autoradiography and estrogen receptor immunohistochemistry.

The nucleus intercollicularis is an important site in the control of vocalization in birds. In oscines, a subregion of the nucleus intercollicularis called the dorso-medial intercollicular nucleus appears to play a key role in this process because it receives the majority of the projections from the nucleus robustus archistriatalis and sends most of the projections to the motor nucleus of the hypoglossal nerve. In this paper, we present neurochemical studies of the nucleus intercollicularis in the Japanese quail which suggest the presence of heterogeneity within this structure. One rostral band contains high densities of cholinergic muscarinic receptors identified by quantitative autoradiography using tritiated N-methylscopolamine as the ligand. A caudal dorso-medial region is specifically labeled by estrogen receptors identified using immunocytochemistry and by alpha 2-adrenergic receptors which were quantified by autoradiography using tritiated para-amino-clonidine. This latter subregion is possibly equivalent to the dorso-medial intercollicular nucleus of oscines. Additional track-tracing studies should be performed to confirm this homology. The coexistence of estrogen and alpha 2-adrenergic receptors within the same structure suggests important functional connections between steroid action and catecholaminergic systems in the brain.