Imaging axonal transport in the rat visual pathway

Abstract

A technique was developed for assaying axonal transport in retinal ganglion cells using 2 µl injections of 1% cholera toxin b-subunit conjugated to AlexaFluor488 (CTB). In vivo retinal and post-mortem brain imaging by confocal scanning laser ophthalmoscopy and post-mortem microscopy were performed. The transport of CTB was sensitive to colchicine, which disrupts axonal microtubules. The bulk rates of transport were determined to be approximately 80–90 mm/day (anterograde) and 160 mm/day (retrograde). Results demonstrate that axonal transport of CTB can be monitored in vivo in the rodent anterior visual pathway, is dependent on intact microtubules, and occurs by active transport mechanisms.

Assessment of retinal ganglion cell damage in glaucomatous optic neuropathy: Axon transport, injury and soma loss

“…Beyond its use as a neuronal tracer (see transport section above), retrogradely transported CTB effectively labels RGC cell bodies in the retina (Abbott et al, 2013(Abbott et al, , 2014. Recent studies from our group have shown CTB labeling in the cytoplasm and axons of RGCs after SC application, showing good correspondence with the RGC marker Brn3a (Fig.…”

“…1D, E, H and I). Disruption of AT by intravitreal injection of colchicine, a toxin that interferes with microtubule polymerization, reduces CTB-Alexa488 staining along all of the intra-retinal RGC plasma membrane (Abbott et al, 2013), confirming that CTB intracellular movement is by active transport.…”

“…To control for variability when control and experimental ONs are imaged separately, they either normalized the intensity values to the pre-laminar region or reported them as a change in intensity between sequential sampling segments. Abbott et al (2013) presented an ex vivo method to qualitatively assess AT in whole rat ONs via confocal scanning laser ophthalmoscopy (CSLO). Following fixation and dissection from the skull, the brain was inverted in a custom CSLO mount, revealing the ONs beneath.…”

“…Following fixation and dissection from the skull, the brain was inverted in a custom CSLO mount, revealing the ONs beneath. CSLO imaging detected CTB-Alexa488 in the ONs after both anterograde and retrograde application (Abbott et al, 2013). This approach avoids time-consuming tissue processing; however, specialized equipment is required and the low image resolution offers limited information on axon health.…”

Impaired Axonal Transport and Glaucoma

“…CTB can be injected intravitreally in mice and rats and detected in the retina, optic nerve and superior colliculus as the molecule is transported along RGCs. 16,17 Visualizing Components Involved in Axonal Transport…”