Concurrent middle cerebral artery occlusion and intra-arterial drug infusion via ipsilateral common carotid artery catheter in the rat

Abstract

Pre-clinical development of therapy for acute ischemic stroke requires robust animal models; the rodent middle cerebral artery occlusion (MCAo) model using a nylon filament inserted into the internal carotid artery is the most popular. Drug screening requires targeted delivery of test substance in a controlled manner. To address these needs, we developed a novel method for delivering substances directly into the ischemic brain during MCAo in the awake rat. An indwelling catheter is placed in the common carotid artery ipsilateral to the occlusion at the time of the surgical placement of the occluding filament. The internal and common carotid arteries are left patent to allow superfusion anterograde. The surgeries can be completed quickly to allow rapid recovery from anesthesia; tests substances can be infused at any given time for any given duration. To simulate clinical scenarios, the occluding filament can be removed minutes or hours later (reperfusion) followed by therapeutic infusions. By delivering drug intra-arterially to the target tissue, "first pass" loss in the liver is reduced and drug effects are concentrated in the ischemic zone. To validate our method, rats were infused with Evans blue dye either intra-arterially or intravenously during a 4 h MCAo. After a 30 min reperfusion period, the dye was extracted from each hemisphere and quantitated with a spectrophotometer. Significantly more dye was measured in the ischemic hemispheres that received the dye intra-arterially.

Figure 1

A. 4-0 Ethilon monofilament with tip heat blunted. The widest part of this particular occlusion monofilament measures 308um. B. Catheter set-up. Top: Saline filled 1 cc syringe with a 27 gauge luer stub adaptor and catheter attached. Bottom: 2 French silicone catheter (0.3mmID × 0.6mm OD) with 3 French retention beads sleeved over the distal beveled end.

Figure 2

Blunt dissection near the intersection of the sternomastoid and the sternohyoid muscles exposed the underlying carotid bifurcation. Using these landmarks sped dissection and eliminated unnecessary exploration.

Figure 3

Set up for the arteriotomy into the external carotid artery (ECA). Note that the vagus nerve has not been included in the clamp on the common carotid.

Figure 4

Schematic showing the monofilament placed in the external (ECA) and coursing up the internal (ICA) carotid arteries.

Figure 5

Schematic of catheter placement in the common carotid artery (CCA).

Figure 6

Catheter and monofilament in place and secured.

Figure 7

Rat in warmed recovery chamber receiving infusion of Evans blue for the period of the middle cerebral artery occlusion. Note the tubing stretched across the top of the cage to serve as a support for the catheter line.

Figure 8

A) Representative photomicrographs illustrating increased Evans blue extravasation into the Intra-arterial (IA) infusion (d) delivered brain, compared to IA sham (b), intravenous (IV) sham (a) and IV infusion (c). Evans blue extravasation is indicated by circle and arrows. B) Measurements of leaked Evans blue dye for the four test groups. IA infusion delivered significantly more substances compared to intravenous IV delivery to the ischemic brain (**two-tailed student t-test, P<0.01).