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Connections of the Superior Paraolivary Nucleus of the Rat: II. Reciprocal Connections with the Tectal Longitudinal Column.

Viñuela A, Aparicio MA, Berrebi AS, Saldaña E - Front Neuroanat (2011)

Bottom Line: SPON fibers reach the TLC by two routes: as collaterals of axons of the CoIC, and as axons that circumvent the ipsilateral IC before traveling in the deep layers of the superior colliculus (SC).The density of these projections identifies SPON as a significant source of input to the TLC.This observation suggests that the SPON is a significant target of TLC projections.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for the Neurobiology of Hearing, Neuroscience Institute of Castilla y León, University of Salamanca Salamanca, Spain.

ABSTRACT
The superior paraolivary nucleus (SPON), a prominent GABAergic center of the mammalian auditory brainstem, projects to the ipsilateral inferior colliculus (IC) and sends axons through the commissure of the IC (CoIC). Herein we demonstrate that the SPON is reciprocally connected with the recently discovered tectal longitudinal column (TLC). The TLC is a long and narrow structure that spans nearly the entire midbrain tectum longitudinally, immediately above the periaqueductal gray matter (PAG) and very close to the midline. Unilateral injections of biotinylated dextran into the SPON of the rat label abundant terminal fibers in the TLC of both sides, with an ipsilateral predominance. The SPON provides a dense innervation of the entire rostrocaudal extent of the ipsilateral TLC, and a relatively sparser innervation of the caudal and rostral portions of the contralateral TLC. SPON fibers reach the TLC by two routes: as collaterals of axons of the CoIC, and as axons that circumvent the ipsilateral IC before traveling in the deep layers of the superior colliculus (SC). The density of these projections identifies SPON as a significant source of input to the TLC. Other targets of the SPON discovered in this study include the deep layers of the SC and the PAG. The same experiments reveal numerous labeled cell bodies in the TLC, interspersed among the labeled SPON fibers. This observation suggests that the SPON is a significant target of TLC projections. The discovery of novel reciprocal connections between the SPON and the TLC opens unexpected avenues for investigation of sound processing in mammalian brainstem circuits.

No MeSH data available.


Related in: MedlinePlus

Distribution of presumed synaptic boutons of SPON fibers in the TLC. (A–F) Plots of the location of all swellings and varicosities of SPON fibers labeled in the same sections of the TLC shown in Figure 3 (Case 97084). Each dot represents one presumed bouton. The number below each TLC indicates the number of labeled boutons.
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Figure 6: Distribution of presumed synaptic boutons of SPON fibers in the TLC. (A–F) Plots of the location of all swellings and varicosities of SPON fibers labeled in the same sections of the TLC shown in Figure 3 (Case 97084). Each dot represents one presumed bouton. The number below each TLC indicates the number of labeled boutons.

Mentions: A similar procedure was used to produce the plots showing the distribution of presumed labeled synaptic boutons in Figures 6 and 7. To convey a clear impression of synaptic bouton density, each plot of Figure 7 was subsequently transferred to a Photoshop document and blurred using a Gaussian filter with a 20-pixel square matrix.


Connections of the Superior Paraolivary Nucleus of the Rat: II. Reciprocal Connections with the Tectal Longitudinal Column.

Viñuela A, Aparicio MA, Berrebi AS, Saldaña E - Front Neuroanat (2011)

Distribution of presumed synaptic boutons of SPON fibers in the TLC. (A–F) Plots of the location of all swellings and varicosities of SPON fibers labeled in the same sections of the TLC shown in Figure 3 (Case 97084). Each dot represents one presumed bouton. The number below each TLC indicates the number of labeled boutons.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3045713&req=5

Figure 6: Distribution of presumed synaptic boutons of SPON fibers in the TLC. (A–F) Plots of the location of all swellings and varicosities of SPON fibers labeled in the same sections of the TLC shown in Figure 3 (Case 97084). Each dot represents one presumed bouton. The number below each TLC indicates the number of labeled boutons.
Mentions: A similar procedure was used to produce the plots showing the distribution of presumed labeled synaptic boutons in Figures 6 and 7. To convey a clear impression of synaptic bouton density, each plot of Figure 7 was subsequently transferred to a Photoshop document and blurred using a Gaussian filter with a 20-pixel square matrix.

Bottom Line: SPON fibers reach the TLC by two routes: as collaterals of axons of the CoIC, and as axons that circumvent the ipsilateral IC before traveling in the deep layers of the superior colliculus (SC).The density of these projections identifies SPON as a significant source of input to the TLC.This observation suggests that the SPON is a significant target of TLC projections.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for the Neurobiology of Hearing, Neuroscience Institute of Castilla y León, University of Salamanca Salamanca, Spain.

ABSTRACT
The superior paraolivary nucleus (SPON), a prominent GABAergic center of the mammalian auditory brainstem, projects to the ipsilateral inferior colliculus (IC) and sends axons through the commissure of the IC (CoIC). Herein we demonstrate that the SPON is reciprocally connected with the recently discovered tectal longitudinal column (TLC). The TLC is a long and narrow structure that spans nearly the entire midbrain tectum longitudinally, immediately above the periaqueductal gray matter (PAG) and very close to the midline. Unilateral injections of biotinylated dextran into the SPON of the rat label abundant terminal fibers in the TLC of both sides, with an ipsilateral predominance. The SPON provides a dense innervation of the entire rostrocaudal extent of the ipsilateral TLC, and a relatively sparser innervation of the caudal and rostral portions of the contralateral TLC. SPON fibers reach the TLC by two routes: as collaterals of axons of the CoIC, and as axons that circumvent the ipsilateral IC before traveling in the deep layers of the superior colliculus (SC). The density of these projections identifies SPON as a significant source of input to the TLC. Other targets of the SPON discovered in this study include the deep layers of the SC and the PAG. The same experiments reveal numerous labeled cell bodies in the TLC, interspersed among the labeled SPON fibers. This observation suggests that the SPON is a significant target of TLC projections. The discovery of novel reciprocal connections between the SPON and the TLC opens unexpected avenues for investigation of sound processing in mammalian brainstem circuits.

No MeSH data available.


Related in: MedlinePlus