Callosal neurones give rise to zinc-rich boutons in the rat visual cortex

Christensen, Mette K.; Reblet, Concepción; Martínez‐Garciá, Fernando; Pérez–Clausell, Jeús; Bueno-López, José Luis

doi:10.1097/00001756-199502000-00023

Cited by 28 publications

(16 citation statements)

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“…This suggests the existence of layer IV, a recipient of sensory information, in the motor cortex of the rat. Since neurons containing a high Zn concentration (a subset of glutamatergic neurons enriched in labile Zn) are generally not found in sensory pathways that run from the thalamus (Casanovas-Aguilar et al, 1995; Dyck et al, 1993; Frederickson et al, 2000), we hypothesized that the presence of a cortical layer IV, although not evident on routine histological assessment, would be portrayed by a cortical band of reduced Zn concentration between layers III and V. XFI was employed in this study to measure the amount of Zn across different layers of forelimb motor cortex.…”

Section: Discussionmentioning

confidence: 99%

“…The rationale behind the study design was based on the previous observation that Zn-containing neurons, a subset of glutamatergic neurons with a high concentration of labile Zn, are generally not found in pathways that run from the thalamus (Casanovas-Aguilar et al, 1995; Dyck et al, 1993; Frederickson et al, 2000). The sensory-motor cortex, since it has a well demarcated layer IV, was used as a positive control region.…”

Section: Introductionmentioning

confidence: 99%

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Laminar-specific distribution of zinc: Evidence for presence of layer IV in forelimb motor cortex in the rat

et al. 2014

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The rat is the most widely studied pre-clinical model system of various neurological and neurodegenerative disorders affecting hand function. Although brain injury to the forelimb region of the motor cortex in rats mostly induces behavioral abnormalities in motor control of hand movements, behavioral deficits in the sensory-motor domain are also observed. This questions the prevailing view that cortical layer IV, a recipient of sensory information from the thalamus, is absent in rat motor cortex. Because zinc-containing neurons are generally not found in pathways that run from the thalamus, an absence of zinc (Zn) in a cortical layer would be suggestive of sensory input from the thalamus. To test this hypothesis, we used synchrotron micro X-ray fluorescence imaging to measure Zn distribution across cortical layers. Zn maps revealed a heterogeneous layered Zn distribution in primary and secondary motor cortices of the forelimb region in the adult rat. Two wider bands with elevated Zn content were separated by a narrow band having reduced Zn content, and this was evident in two rat strains. The Zn distribution pattern was comparable to that in sensorimotor cortex, which is known to contain a well demarcated layer IV. Juxtaposition of Zn maps and the images of brain stained for Nissl bodies revealed a “Zn valley” in primary motor cortex, apparently starting at the ventral border of pyramidal layer III and ending at the close vicinity of layer V. This finding indicates the presence of a conspicuous cortical layer between layers III and V, i.e. layer IV, the presence of which previously has been disputed. The results have implications for the use of rat models to investigate human brain function and neuropathology, such as after stroke. The presence of layer IV in the forelimb region of the motor cortex suggests that therapeutic interventions used in rat models of motor cortex injury should target functional abnormalities in both motor and sensory domains. The finding is also critical for future investigation of the biochemical mechanisms through which therapeutic interventions can enhance neural plasticity, particularly through Zn dependent pathways.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laminar-specific distribution of zinc: Evidence for presence of layer IV in forelimb motor cortex in the rat

et al. 2014

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“…An alternative second method, used here, is to make focal injections of sodium selenite. Focal injections are less toxic in primates and have the further advantage of selectively labeling only those Zn+ neurons that project to the injection site (Christensen et al 1992; Casanovas-Aguilar et al 1995, 1998; Brown and Dyck 2005). …”

Section: Methodsmentioning

confidence: 99%

Pathway-Specific Utilization of Synaptic Zinc in the Macaque Ventral Visual Cortical Areas

et al. 2010

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Synaptic zinc is an activity-related neuromodulator, enriched in hippocampal mossy fibers and a subset of glutamatergic cortical projections, exclusive of thalamocortical or corticothalamic. Some degree of pathway specificity in the utilization of synaptic zinc has been reported in rodents. Here, we use focal injections of the retrograde tracer sodium selenite to identify zinc-positive (Zn+) projection neurons in the monkey ventral visual pathway. After injections in V1, V4, and TEO areas, neurons were detected preferentially in several feedback pathways but, unusually, were restricted to deeper layers without involvement of layers 2 or 3. Temporal injections resulted in more extensive labeling of both feedback and intratemporal association pathways. The Zn+ neurons had a broader laminar distribution, similar to results from standard retrograde tracers. After anterograde tracer injection in area posterior TE, electron microscopic analysis substantiated that a proportion of feedback synapses was colabeled with zinc. Nearby injections, Zn+ intrinsic neurons concentrated in layer 2, but in temporal areas were also abundant in layer 6. These results indicate considerable pathway and laminar specificity as to which cortical neurons use synaptic zinc. Given the hypothesized roles of synaptic zinc, this is likely to result in distinct synaptic properties, possibly including differential synaptic plasticity within or across projections.

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“…Most associative and commissural axons emerge from pyramidal cells sited in layers 2/3 and 5-6, and also from spiny inverted pyramidal cells and other polymorphic cells of layers 5-6 [23,27,28]. The axons of all these cells extend forward to innervate the layer 4 of cortical areas of higher-order hierarchy [23,[27][28][29][30]. This is the so-called associative forward projection [31].…”

Section: Principal Cells Of Intratelencephalic Projection (Inclusive mentioning

confidence: 99%

Projections, Partaken Circuits and Axon Initial Segments of Cortical Principal Neurons

Bueno‐López¹,

Chara²,

Mendizabal-Zubiaga³

et al. 2012

Visual Cortex - Current Status and Perspectives

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Callosal neurones give rise to zinc-rich boutons in the rat visual cortex

Cited by 28 publications

References 0 publications

Laminar-specific distribution of zinc: Evidence for presence of layer IV in forelimb motor cortex in the rat

Laminar-specific distribution of zinc: Evidence for presence of layer IV in forelimb motor cortex in the rat

Pathway-Specific Utilization of Synaptic Zinc in the Macaque Ventral Visual Cortical Areas

Projections, Partaken Circuits and Axon Initial Segments of Cortical Principal Neurons

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