The efficacy of the fluorescent conjugates of cholera toxin subunit B for multiple retrograde tract tracing in the central nervous system

Conte, William L.; Kamishina, Hiroaki; Reep, Roger L.

doi:10.1007/s00429-009-0212-x

Cited by 49 publications

(47 citation statements)

References 26 publications

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“…For example, the BA is the only region of the amygdala that receives robust input from the ventral CA1 area of the hippocampus (Pitkanen et al, 2000). Given that cholera toxin is a selective monosynaptic retrograde tracer (Bruce and Grofova, 1992; Conte et al, 2009), we are confident that the CTb labeling we have observed reflects specific afferent projections of the BA.…”

Section: Discussionmentioning

confidence: 70%

Hippocampal and Prefrontal Projections to the Basal Amygdala Mediate Contextual Regulation of Fear after Extinction

Orsini¹,

Kim²,

Knapska³

et al. 2011

J. Neurosci.

279

277

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Knowing when and where to express fear is essential to survival. Recent work in fear extinction paradigms reveals that the contextual regulation of fear involves a neural network involving the hippocampus, medial prefrontal cortex and amygdala. The amygdaloid basal nuclei (BA) receive convergent input from the ventral hippocampus (VH) and prelimbic (PL) prefrontal cortex, and may integrate VH and PL input to regulate fear expression. To examine the functional organization of this neural circuit, we used cellular imaging of c-fos expression in anatomically defined neuronal populations and circuit disconnections to identify the pathways involved in the contextual control of extinguished fear. Prior to behavioral testing, we infused a retrograde tracer into the amygdala to label BA-projecting neurons in VH and PL. Rats then underwent fear conditioning and extinction and were tested for their fear to the extinguished conditioned stimulus (CS) in either the extinction context or in another context; freezing behavior served as the index of conditional fear. CS presentation outside the extinction context renewed conditional freezing, and was associated with significantly more c-fos expression in BA-projecting neurons in the VH and PL than that induced by CS presentation in the extinction context. We next examined whether direct or indirect projections of VH to BA mediate fear renewal. Interestingly, disconnections of the VH from either the BA or PL eliminated renewal. These findings suggest that convergent inputs from both the ventral hippocampus and prelimbic cortex in the basal amygdala mediate the contextual control of fear after extinction.

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Section: Discussionmentioning

confidence: 70%

Hippocampal and Prefrontal Projections to the Basal Amygdala Mediate Contextual Regulation of Fear after Extinction

Orsini¹,

Kim²,

Knapska³

et al. 2011

J. Neurosci.

279

277

View full text Add to dashboard Cite

show abstract

“…Anatomical tracers have occasionally been reported to preferentially bind to certain projections (Schofield et al 2007; Deng and Rogers 1999) and we cannot completely rule out that the differences in the percentage of double-labeled cells in reuniens compared to the subiculum do not result from biases in the binding of CTB-AF conjugates. Nonetheless, CTB is considered a sensitive retrograde tracer (Conte et al 2009) and enters cells by binding to gangliosides in the cell membrane (Stoeckel 1977; Joseph et al 1978). One advantage of CTB conjugates for collateralization studies is that using the same compound minimizes the variability in the spread, uptake and transport that would result from using multiple tracers in the same animal (Conte et al 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Nonetheless, CTB is considered a sensitive retrograde tracer (Conte et al 2009) and enters cells by binding to gangliosides in the cell membrane (Stoeckel 1977; Joseph et al 1978). One advantage of CTB conjugates for collateralization studies is that using the same compound minimizes the variability in the spread, uptake and transport that would result from using multiple tracers in the same animal (Conte et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Anatomical substrates for direct interactions between hippocampus, medial prefrontal cortex, and the thalamic nucleus reuniens

et al. 2013

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The reuniens nucleus in the midline thalamus projects to the medial prefrontal cortex (mPFC) and the hippocampus, and has been suggested to modulate interactions between these regions, such as spindle–ripple correlations during sleep and theta band coherence during exploratory behavior. Feedback from the hippocampus to the nucleus reuniens has received less attention but has the potential to influence thalamocortical networks as a function of hippocampal activation. We used the retrograde tracer cholera toxin B conjugated to two fluorophores to study thalamic projections to the dorsal and ventral hippocampus and to the prelimbic and infralimbic subregions of mPFC. We also examined the feedback connections from the hippocampus to reuniens. The goal was to evaluate the anatomical basis for direct coordination between reuniens, mPFC, and hippocampus by looking for double-labeled cells in reuniens and hippocampus. In confirmation of previous reports, the nucleus reuniens was the origin of most thalamic afferents to the dorsal hippocampus, whereas both reuniens and the lateral dorsal nucleus projected to ventral hippocampus. Feedback from hippocampus to reuniens originated primarily in the dorsal and ventral subiculum. Thalamic cells with collaterals to mPFC and hippocampus were found in reuniens, across its anteroposterior axis, and represented, on average, about 8 % of the labeled cells in reuniens. Hippocampal cells with collaterals to mPFC and reuniens were less common (~1 % of the labeled subicular cells), and located in the molecular layer of the subiculum. The results indicate that a subset of reuniens cells can directly coordinate activity in mPFC and hippocampus. Cells with collaterals in the hippocampus–reuniens–mPFC network may be important for the systems consolidation of memory traces and for theta synchronization during exploratory behavior.

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“…In order to identify lateral entorhinal cortical (LEC) cells with afferent projections to CA3, all rats received bilateral injections of the retrograde tracer cholera toxin subunit B (recombinant) Alexa Fluor 594 (CTB; ThermoFisher Scientific, cat # C22842) (Conte et al, 2009a,b) targeting the CA3 region (Paxinos and Watson, 2007). CTB (500 μg) was reconstituted and diluted to 1% in 50 μl of sterile 0.1 M PBS and stored at −20°C until surgery.…”

Section: Methodsmentioning

confidence: 99%

“…This approach was used to quantify the extent to which the active CA3 ensemble updated across different environments, and if this related to a rat's ability to discriminate between two similar objects. Furthermore, Arc catFISH was combined with retrograde tracing to identify those LEC neurons that project directly to CA3 (Conte et al, 2009a,b; Mesina et al, 2016). Importantly, analysis of the entorhinal cortex was restricted to the lateral area.…”

Section: Introductionmentioning

confidence: 99%

Age-related Changes in Lateral Entorhinal and CA3 Neuron Allocation Predict Poor Performance on Object Discrimination

Maurer

Johnson

Hernandez

et al. 2017

Front. Syst. Neurosci.

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Age-related memory deficits correlate with dysfunction in the CA3 subregion of the hippocampus, which includes both hyperactivity and overly rigid activity patterns. While changes in intrinsic membrane currents and interneuron alterations are involved in this process, it is not known whether alterations in afferent input to CA3 also contribute. Neurons in layer II of the lateral entorhinal cortex (LEC) project directly to CA3 through the perforant path, but no data are available regarding the effects of advanced age on LEC activity and whether these activity patterns update in response to environmental change. Furthermore, it is not known the extent to which age-related deficits in sensory discrimination relate to the inability of aged CA3 neurons to update in response to new environments. Young and aged rats were pre-characterized on a LEGO© object discrimination task, comparable to behavioral tests in humans in which CA3 hyperactivity has been linked to impairments. The cellular compartment analysis of temporal activity with fluorescence in situ hybridization for the immediate-early gene Arc was then used to identify the principal cell populations that were active during two distinct epochs of random foraging in different environments. This approach enabled the extent to which rats could discriminate two similar objects to be related to the ability of CA3 neurons to update across different environments. In both young and aged rats, there were animals that performed poorly on the LEGO object discrimination task. In the aged rats only, however, the poor performers had a higher percent of CA3 neurons that were active during random foraging in a novel environment, but this is not related to the ability of CA3 neurons to remap when the environment changed. Afferent neurons to CA3 in LEC, as identified with the retrograde tracer choleratoxin B (CTB), also showed a higher percentage of cells that were positive for Arc mRNA in aged poor performing rats. This suggests that LEC contributes to the hyperactivity seen in CA3 of aged animals with object discrimination deficits and age-related cognitive decline may be the consequence of dysfunction endemic to the larger network.

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The efficacy of the fluorescent conjugates of cholera toxin subunit B for multiple retrograde tract tracing in the central nervous system

Cited by 49 publications

References 26 publications

Hippocampal and Prefrontal Projections to the Basal Amygdala Mediate Contextual Regulation of Fear after Extinction

Hippocampal and Prefrontal Projections to the Basal Amygdala Mediate Contextual Regulation of Fear after Extinction

Anatomical substrates for direct interactions between hippocampus, medial prefrontal cortex, and the thalamic nucleus reuniens

Age-related Changes in Lateral Entorhinal and CA3 Neuron Allocation Predict Poor Performance on Object Discrimination

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