Chemoarchitectonic subdivisions of the songbird septum and a comparative overview of septum chemical anatomy in jawed vertebrates

Abstract

Available data demonstrate that the avian septal region shares a number of social behavior functions and neurochemical features in common with mammals. However, the structural and functional subdivisions of the avian septum remain largely unexplored. In order to delineate chemoarchitectural zones of the avian septum, we prepared a large dataset of double-, triple-, and quadruple-labeled material in a variety of songbird species (finches and waxbills of the family Estrildidae and a limited number of emberizid sparrows) using antibodies against 10 neuropeptides and enzymes. Ten septal zones were identified that were placed into lateral, medial, caudocentral, and septohippocampal divisions, with the lateral and medial divisions each containing multiple zones. The distributions of numerous immunoreactive substances in the lateral septum closely match those of mammals (i.e., distributions of met-enkephalin, vasotocin, galanin, calcitonin gene-related peptide, tyrosine hydroxylase, vasoactive intestinal polypeptide, substance P, corticotropin-releasing factor, and neuropeptide Y), enabling detailed comparisons with numerous chemoarchitectonic zones of the mammalian lateral septum. Our septohippocampal and caudocentral divisions are topographically comparable to the mammalian septohippocampal and septofimbrial nuclei, respectively, although additional data will be required to establish homology. The present data also demonstrate the presence of a medial septal nucleus that is histochemically comparable to the medial septum of mammals. The avian medial septum is clearly defined by peptidergic markers and choline acetyltransferase immunoreactivity. These findings should provide a useful framework for functional and comparative studies, as they suggest that many features of the septum are highly conserved across vertebrate taxa.

Neuropeptide binding reflects convergent and divergent evolution in species-typical group sizes

“…Where appropriate, we have adopted this new nomenclature, although the majority of structures discussed here lie within basal forebrain regions that did not receive new names with the recent revision. Our nomenclature for these sites is consistent with our previous investigations in songbirds (see Goodson and Evans, 2004 for area delineations; also Goodson et al, 2005a), and we have employed the nomenclature of Goodson et al (2004a) for the various subdivisions of the septal complex.…”

“…However, major nuclei and gross structure (ventricles, fiber tracts) can be visualized in this manner. Importantly, based on extensive histochemical studies of four estrildid finches and one sparrow species (Goodson et al, 2004a), we have been able to develop methods for localizing areas of interest (e.g., septal zones and major hypothalamic areas) on the basis of major structural landmarks, typically by considering relative distances between them. Once the area has been localized, templates are superimposed on digital images of the sections.…”

Increased expression level of corticotropin-releasing hormone in the amygdala and in the hypothalamus in rats exposed to chronic unpredictable mild stress

“…The test was performed before CUMS, on day 7 of CUMS, and on day 21 of CUMS, respectively. The primary antibody specificity had been identified earlier [20] . The specificity of CRH antibody was tested by preadsorbing primary antibody with the CRH peptide (10 μmol/L, Bachem) overnight.…”

Neural responses to aggressive challenge correlate with behavior in nonbreeding sparrows

“…Both primary antibodies were used at a concentration of 1:1000 and were labeled using a goat anti-rabbit secondary antibody conjugated to Alexa Fluor 594 (Molecular Probes). Details of our immunocytochemical procedure, including materials and concentrations, have been published elsewhere, as have our methods for IEG quantification [1,16]. Specificities of the primary antisera have also been fully addressed [1,17].…”

“…IEG quantification and the delineation of brain regions were conducted using the methods previously employed for song sparrows [1] and the chemoarchitectural parcellation of the LS recently established for songbirds (including song sparrows) [16]. IEG quantification was performed blind to subject groups.…”