Cannula Implantation into the Cisterna Magna of Rodents

Abstract

Cisterna magna cannulation (CMc) is a straightforward procedure that enables direct access to the cerebrospinal fluid (CSF) without operative damage to the skull or the brain parenchyma. In anesthetized rodents, the exposure of the dura mater by blunt dissection of the neck muscles allows the insertion of a cannula into the cisterna magna (CM). The cannula, composed either by a fine beveled needle or borosilicate capillary, is attached via a polyethylene (PE) tube to a syringe. Using a syringe pump, molecules can then be injected at controlled rates directly into the CM, which is continuous with the subarachnoid space. From the subarachnoid space, we can trace CSF fluxes by convective flow into the perivascular space around penetrating arterioles, where solute exchange with the interstitial fluid (ISF) occurs. CMc can be performed for acute injections immediately following the surgery, or for chronic implantation, with later injection in anesthetized or awake, freely moving rodents. Quantitation of tracer distribution in the brain parenchyma can be performed by epifluorescence, 2-photon microscopy, and magnetic resonance imaging (MRI), depending on the physico-chemical properties of the injected molecules. Thus, CMc in conjunction with various imaging techniques offers a powerful tool for assessment of the glymphatic system and CSF dynamics and function. Furthermore, CMc can be utilized as a conduit for fast, brain-wide delivery of signaling molecules and metabolic substrates that could not otherwise cross the blood brain barrier (BBB).

PDGF-B Is Required for Development of the Glymphatic System

“…To map the dynamic pattern of perivascular CSF tracer influx, in real time we injected tracers into the CSF of the cisterna magna and imaged the anesthetized mice through the intact skull ( Xavier et al, 2018 ). In P1 mice, in vivo imaging showed slow tracer influx primarily into the hindbrain, while the cortex and the olfactory bulb were almost devoid of tracer influx ( Figures 2A and 2B ).…”

In vivo T1 mapping for quantifying glymphatic system transport and cervical lymph node drainage

“…Through a midline incision, the atlanto-occipital membrane was exposed and a 34-ga shortened needle (Hamilton, US) connected via polyurethane tubing to a 50 µl Hamilton syringe (Hamilton, US) mounted in a micro-infusion pump (Legato 130, KD Scientific, Holliston, MA, USA) was inserted into the CM. Previous studies reporting on tracer delivery for GS transport studies in mice via the CM have used infusion rates of 0.1-2 µl/ min for a total volume of 5-10 µl 22,[37][38][39][40] . In this study we infused 7 µl of Gd-DOTA (Guerbet LLC, Princeton, NJ, US) prepared as a 1:20 dilution in sterile 0.9% NaCl or 7 µl of sterile 0.9% NaCl at an infusion rate of 1 µl/min.…”

Is Vagus Nerve Stimulation Brain Washing?

“…Additionally, visual confirmation of the Hering-Breuer reflex, which causes a brief cessation of breathing to prevent lung over-inflation, and is characteristic of VNS, was observed in most but not all animals. After confirming engagement, experimental animals received the clinically derived VNS over the course of 1 hour, and the degree of CSF penetrance was quantified by the spread of a fluorescent dye injected into the cisterna magna (CM) using previously established methods (14,33). Following perfusion, the fractional area to which the dye had spread was measured using a thresholding algorithm as previously described (14).…”

“…Injection of a fluorescent tracer into the CSF system via the CM was performed as previously described (14,33). Briefly, after vagus nerve cuff implantation, the mice were carefully placed into a stereotax with the head at a slight downward angle to provide access to the CM.…”