Glass-plastic push-pull cannula system for regional perfusion of sites in the brain

A new non-metallic push-pull cannula device is described for the localized perfusion of brain sites in the rat or other animal. Comprised entirely of glass and plastic materials, the cannula is intended for usage in an experiment in which the presence in tissue of metal tubing for delivery of perfusate is methodologically inappropriate. The main features of the cannula include its light weight, a Delrin pedestal base, a micro-glass guide tube, a polyethylene stylet, plastic spacers for adjustment of depth of perfusion, a protective cap for the chronic maintenance of the preparation, low cost and re-usability. The push-pull cannula is of concentric design and is fashioned from glass capillary and polyethylene tubing which are bonded at their common junctions by an epoxy cement. During a push-pull perfusion a special perfusion cap is used not only to hold the cannula firmly in place but also to protect the glass components from external damage. To further coincide with the metal-free requirements of the preparation, bone screws of nylon are used during the surgical implantation of the pedestal base. A prototype experiment illustrating its use in an unrestrained animal also is presented. The special applications for this cannula system are discussed which include its usage in experiments in either the anesthetized or unanesthetized rat exposed to microwave radiation where the presence of metal in the field would result in unwanted 'hot spots' in the cerebral tissue.