A practical method for simultaneous multiple intracerebral implantations for microdialysis in rats.

Many experimental designs require the chronic implantation of different elements destined to act as channels that facilitate the information conveyance between the brain and some external devices or vice versa. Electrodes for electrophysiological or electrochemical recording or brain stimulation, and guide shafts for drug administration or chemical monitoring of the extracellular space are the most common examples of channels serving those purposes. The stereotaxic implantation of one or more of those experimental tools in the same antero-posterior plane is relatively easy, but surgery is nonetheless more complicated when two or more elements have to be placed using totally different coordinates. In those cases the current strategy consists in the successive implantation of the elements, waiting for the hardening of the dental acrylic destined to fix one of them in place before dealing with the next. This procedure takes time, is considerably more laborious than surgery for single elements and is particularly difficult when the elements have to be implanted in close proximity. The present report describes a method that simplifies surgery for multiple intracerebral implantation and allows the simultaneous and exact placement of as many electrodes or guide shafts as is practical in any experimental design. The method requires the previous construction of a jig or template designed to temporarily hold the elements to be implanted, allowing them to assume and keep the same positional relationship that they should have when definitively in place within the skull. The design may vary according to the type of elements to be implanted and the coordinates required for each particular experiment, but here it is illustrated describing the assembly of a particular jig for the simultaneous implantation of guide shafts for ulterior microdialysis in the prefrontal cortex (PFC), nucleus accumbens (NAC) and striatum (STR). Some rules can be derived from this particular case to make the method a more general one and suitable for any combination of elements and stereotaxic coordinates.