CHARACTERIZATION AND APPLICATION OF MICRODIALYSIS PROBES WITH AN ACTIVE EXCHANGE LENGTH COMPATIBLE WITH SMALL-SIZE BRAIN NUCLEI IN THE RAT

We communicated the construction, characterization and application of microdialysis probes with an active exchange length that is suitable f or experiments involving small-size nuclei in rat brain. Using substan ce P (SP) as the test substance, we determined that probes with an act ive exchange length of 180-200 mu m exhibited an in vitro recovery of 14.2 +/- 0.8% and in vivo recovery at the nucleus tractus solitarii (N TS) of 24.9 +/- 1.7% for the undecapeptide, calibrated at an infusion rate of 1 mu l/min. We also demonstrated that microinfusion of SP via these probes into the NTS allowed for a correlation of changes in tiss ue levels of both SP (exogenous substance) and norepinephrine (endogen ous substance) with alterations in baroreceptor reflex responses (phys iologic phenomenon).