By comparison, the interpretation of anatomical connections using GdDOTA-CTB is simpler; it has all the properties of a classic neural tracer, without requiring animal sacrifice. Presumably, future applications of the GdDOTA-CTB approach (perhaps in combination with other MRI-based techniques, such as DTI, resting state fMRI, and/or MEMRI) will furnish a much richer in vivo diagram of brain circuitry. At a practical level, this MR-visible tracer can be used to target anatomically connected regions, using electrophysiological microelectrodes and/or serial tracer injections. More generally, this in vivo approach can reveal changes

occurring during plasticity induced by normal or abnormal physiology (e.g., axonal pruning or sprouting), in both central SKI-606 in vivo and peripheral nervous systems (Rakic et al., 1986, LaMantia and Rakic, 1990, Wu and Kaas, 2000, Wu and Kaas, 2002, Raff et al., 2002, Medana and Esiri, 2003 and Prince et al., 2009). GdDOTA-CTB was made

in-house using commercially available products. The detailed synthesis procedures are described in the Supplemental Information. Gd-Albumin was purchased commercially (Biopal Inc, Worcester, MA; cat# P-00P01-100) and was lyophilized and rediluted in double distilled water to a final concentration of 30% in protein and 65 mM in Gd solution. Forty-one adult Sprague-Dawley rats (280–350 g) were used in these experiments (29 injected with GdDOTA-CTB, 4 GdDOTA injections, 3 Gd-Albumin injections, 1 saline injection, and 4 MnCl2 injections). Selleckchem Vorinostat In experiments #1–3, a total of 24

rats received unilateral intracortical injections of GdDOTA-CTB into area S1, and Adenosine 1 received saline injection into area S1. In experiment #4, 4 rats received injections of GdDOTA in area S1 and 3 received injections of Gd-Albumin in S1. In experiment #5, we compared injections of manganese chloride (MnCl2; n = 4) with GdDOTA-CTB to measure diffusion and transport dynamics in both the S1 injection site and the thalamic transport zones. In experiment #6, 4 additional rats received a unilateral injection of GdDOTA-CTB in the nostril cavity (n = 2) or the OB (n = 2). One additional rat was scanned for 14 hr ex vivo, 7 days after an S1 injection of GdDOTA-CTB. All experiments were performed in compliance with guidelines set by the ACUC of the NINDS, NIH. Surgical details and procedures regarding the injections are given in Supplemental Information. Animals were imaged prior to injection (“baseline”), and immediately (1–2 hr) after injection, on days 1–7 postinjection, and at longer intervals for up to 2 months postinjection. Four animals were imaged for 7–10 days postinjection, then sacrificed for histology. GdDOTA alone was injected into the S1 forepaw, using the same coordinates as in the GdDOTA-CTB experiments. MRI data were acquired at the baseline, immediately after injection, and every 12 hr until day 2. The last image was acquired on day 5 postinjection.