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Subdivisions of the auditory midbrain (n. mesencephalicus lateralis, pars dorsalis) in zebra finches using calcium-binding protein immunocytochemistry.

Logerot P, Krützfeldt NO, Wild JM, Kubke MF - PLoS ONE (2011)

Bottom Line: The staining patterns resulting from the application of parvalbumin, calbindin and calretinin antibodies differed from each other and in different parts of the nucleus.MLd.O largely surrounds MLd.I and is distinct from the surrounding intercollicular nucleus.Unlike the case in some non-songbirds, however, the two MLd regions do not correspond to the terminal zones of the projections of the brainstem auditory nuclei angularis and laminaris, which have been found to overlap substantially throughout the nucleus in zebra finches.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, and Centre for Brain Research, University of Auckland, Auckland, New Zealand.

ABSTRACT
The midbrain nucleus mesencephalicus lateralis pars dorsalis (MLd) is thought to be the avian homologue of the central nucleus of the mammalian inferior colliculus. As such, it is a major relay in the ascending auditory pathway of all birds and in songbirds mediates the auditory feedback necessary for the learning and maintenance of song. To clarify the organization of MLd, we applied three calcium binding protein antibodies to tissue sections from the brains of adult male and female zebra finches. The staining patterns resulting from the application of parvalbumin, calbindin and calretinin antibodies differed from each other and in different parts of the nucleus. Parvalbumin-like immunoreactivity was distributed throughout the whole nucleus, as defined by the totality of the terminations of brainstem auditory afferents; in other words parvalbumin-like immunoreactivity defines the boundaries of MLd. Staining patterns of parvalbumin, calbindin and calretinin defined two regions of MLd: inner (MLd.I) and outer (MLd.O). MLd.O largely surrounds MLd.I and is distinct from the surrounding intercollicular nucleus. Unlike the case in some non-songbirds, however, the two MLd regions do not correspond to the terminal zones of the projections of the brainstem auditory nuclei angularis and laminaris, which have been found to overlap substantially throughout the nucleus in zebra finches.

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Patterns of parvalbumin-like immunoreactivity (PV-LI).A–D: caudal (top) to rostral (bottom) coronal sections showing PV-LI through the right MLd of a female zebra finch delineating two regions within the nucleus: MLd.O and MLd.I. The asterisk in B indicates the small nucleus within MLd.O that shows a different staining pattern. (DM is outlined for comparison with Figure 6.). E–G: high magnifications views of areas boxed in A and B. E: Photomicrograph of MLd.I (inset E in panel A) showing the specific neuropil staining and low punctuate density of this region. F: Photomicrograph of MLd.O (inset F in panel A) depicting the neuropil staining, high punctuate density and somata with visible processes specific to this region. G: high magnification view of the region marked by an asterisk in B. Note the darker neuropil staining than that of MLd.O and the absence of punctuate staining. H: Photomicrograph of a Nissl stained section also shown in Figure 5B, showing the dorsomedial MLd subnucleus marked with an asterisk in B. Scale bar: A–D = 100 µm; E–G = 50 µm.
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pone-0020686-g002: Patterns of parvalbumin-like immunoreactivity (PV-LI).A–D: caudal (top) to rostral (bottom) coronal sections showing PV-LI through the right MLd of a female zebra finch delineating two regions within the nucleus: MLd.O and MLd.I. The asterisk in B indicates the small nucleus within MLd.O that shows a different staining pattern. (DM is outlined for comparison with Figure 6.). E–G: high magnifications views of areas boxed in A and B. E: Photomicrograph of MLd.I (inset E in panel A) showing the specific neuropil staining and low punctuate density of this region. F: Photomicrograph of MLd.O (inset F in panel A) depicting the neuropil staining, high punctuate density and somata with visible processes specific to this region. G: high magnification view of the region marked by an asterisk in B. Note the darker neuropil staining than that of MLd.O and the absence of punctuate staining. H: Photomicrograph of a Nissl stained section also shown in Figure 5B, showing the dorsomedial MLd subnucleus marked with an asterisk in B. Scale bar: A–D = 100 µm; E–G = 50 µm.

Mentions: The general parvalbumin staining pattern in MLd described by us [19] was shown to overlap closely the area in receipt of ascending brainstem auditory afferents, thereby defining the boundaries of MLd (Figure 1). Here we describe regional differences in the pattern of staining in more detail. Two regions within MLd were defined by the PV-LI: inner (MLd.I) and outer (MLd.O) (Figure 2, A–D). MLd.O was characterized by a PV-LI positive neuropil and by the presence of stained fibers and stained and unstained somata (Figure 2, F). (For descriptive purposes, we differentiate between staining of fibers within the neuropil and the rest of the neuropil.) The neuropil in this region showed a dense punctate staining pattern, whereas many of its neurons presented stained processes and those along the lateral edge of MLd exhibited elongated somata concentric with the overlying ventricle (not shown). At the level of DM, a small region on the dorsomedial aspect of MLd that can be identified in Nissl stained sections (Figure 2, B-asterisk, G, H-asterisk) exhibited a staining pattern distinct from that of the MLd.O. This small region had a darker PV-LI positive neuropil, stained fibers and stained somata and processes, but was characterized by an absence of punctate staining.


Subdivisions of the auditory midbrain (n. mesencephalicus lateralis, pars dorsalis) in zebra finches using calcium-binding protein immunocytochemistry.

Logerot P, Krützfeldt NO, Wild JM, Kubke MF - PLoS ONE (2011)

Patterns of parvalbumin-like immunoreactivity (PV-LI).A–D: caudal (top) to rostral (bottom) coronal sections showing PV-LI through the right MLd of a female zebra finch delineating two regions within the nucleus: MLd.O and MLd.I. The asterisk in B indicates the small nucleus within MLd.O that shows a different staining pattern. (DM is outlined for comparison with Figure 6.). E–G: high magnifications views of areas boxed in A and B. E: Photomicrograph of MLd.I (inset E in panel A) showing the specific neuropil staining and low punctuate density of this region. F: Photomicrograph of MLd.O (inset F in panel A) depicting the neuropil staining, high punctuate density and somata with visible processes specific to this region. G: high magnification view of the region marked by an asterisk in B. Note the darker neuropil staining than that of MLd.O and the absence of punctuate staining. H: Photomicrograph of a Nissl stained section also shown in Figure 5B, showing the dorsomedial MLd subnucleus marked with an asterisk in B. Scale bar: A–D = 100 µm; E–G = 50 µm.
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pone-0020686-g002: Patterns of parvalbumin-like immunoreactivity (PV-LI).A–D: caudal (top) to rostral (bottom) coronal sections showing PV-LI through the right MLd of a female zebra finch delineating two regions within the nucleus: MLd.O and MLd.I. The asterisk in B indicates the small nucleus within MLd.O that shows a different staining pattern. (DM is outlined for comparison with Figure 6.). E–G: high magnifications views of areas boxed in A and B. E: Photomicrograph of MLd.I (inset E in panel A) showing the specific neuropil staining and low punctuate density of this region. F: Photomicrograph of MLd.O (inset F in panel A) depicting the neuropil staining, high punctuate density and somata with visible processes specific to this region. G: high magnification view of the region marked by an asterisk in B. Note the darker neuropil staining than that of MLd.O and the absence of punctuate staining. H: Photomicrograph of a Nissl stained section also shown in Figure 5B, showing the dorsomedial MLd subnucleus marked with an asterisk in B. Scale bar: A–D = 100 µm; E–G = 50 µm.
Mentions: The general parvalbumin staining pattern in MLd described by us [19] was shown to overlap closely the area in receipt of ascending brainstem auditory afferents, thereby defining the boundaries of MLd (Figure 1). Here we describe regional differences in the pattern of staining in more detail. Two regions within MLd were defined by the PV-LI: inner (MLd.I) and outer (MLd.O) (Figure 2, A–D). MLd.O was characterized by a PV-LI positive neuropil and by the presence of stained fibers and stained and unstained somata (Figure 2, F). (For descriptive purposes, we differentiate between staining of fibers within the neuropil and the rest of the neuropil.) The neuropil in this region showed a dense punctate staining pattern, whereas many of its neurons presented stained processes and those along the lateral edge of MLd exhibited elongated somata concentric with the overlying ventricle (not shown). At the level of DM, a small region on the dorsomedial aspect of MLd that can be identified in Nissl stained sections (Figure 2, B-asterisk, G, H-asterisk) exhibited a staining pattern distinct from that of the MLd.O. This small region had a darker PV-LI positive neuropil, stained fibers and stained somata and processes, but was characterized by an absence of punctate staining.

Bottom Line: The staining patterns resulting from the application of parvalbumin, calbindin and calretinin antibodies differed from each other and in different parts of the nucleus.MLd.O largely surrounds MLd.I and is distinct from the surrounding intercollicular nucleus.Unlike the case in some non-songbirds, however, the two MLd regions do not correspond to the terminal zones of the projections of the brainstem auditory nuclei angularis and laminaris, which have been found to overlap substantially throughout the nucleus in zebra finches.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, and Centre for Brain Research, University of Auckland, Auckland, New Zealand.

ABSTRACT
The midbrain nucleus mesencephalicus lateralis pars dorsalis (MLd) is thought to be the avian homologue of the central nucleus of the mammalian inferior colliculus. As such, it is a major relay in the ascending auditory pathway of all birds and in songbirds mediates the auditory feedback necessary for the learning and maintenance of song. To clarify the organization of MLd, we applied three calcium binding protein antibodies to tissue sections from the brains of adult male and female zebra finches. The staining patterns resulting from the application of parvalbumin, calbindin and calretinin antibodies differed from each other and in different parts of the nucleus. Parvalbumin-like immunoreactivity was distributed throughout the whole nucleus, as defined by the totality of the terminations of brainstem auditory afferents; in other words parvalbumin-like immunoreactivity defines the boundaries of MLd. Staining patterns of parvalbumin, calbindin and calretinin defined two regions of MLd: inner (MLd.I) and outer (MLd.O). MLd.O largely surrounds MLd.I and is distinct from the surrounding intercollicular nucleus. Unlike the case in some non-songbirds, however, the two MLd regions do not correspond to the terminal zones of the projections of the brainstem auditory nuclei angularis and laminaris, which have been found to overlap substantially throughout the nucleus in zebra finches.

Show MeSH
Related in: MedlinePlus