Retrograde and Anterograde Neural Tracing

Experiments involving neural pathway-tracing were as follows: (Exp. 2) Retrograde tracing from the dpLHA following unilateral pressure injection of either Fluorogold (FG, Fluorochrome LLC, Denver, CO; 2% in 0.9% NaCl), or cholera toxin B subunit conjugated to (red fluorophore) Alexa Fluor 594 (CTB-AF594, 0.25% in 0.9% NaCl, Life Technologies, Carlsbad, CA; Cat. No. C-22842). Pressure injections were performed using a microinfusion pump as described above; injection volumes were 100 nl (Exp. 4). Anterograde tracing from the vHP field CA1 following unilateral iontophoretic injection of Phaseolus vulgaris-leucoagglutinin (PHAL, Vector Labs, Burlingame, CA; 2.5% in 0.1 M sodium phosphate-buffered saline, pH 7.4) was performed using a precision current source (digital midgard precision current source, Stoelting) as described previously (Hahn and Swanson, 2010 (link)). PHAL immunoreactive axons in the LHA confirmed the exclusively ipsilateral nature of vHP to LHA projections (Figure 6—figure supplement 1; representative vHP PHAL injection site, Figure 6).