On the choice of so-called placebo solution for the intranigral microinjection in the rat

Rats moving freely in their cages were injected into substantia nigra with bidistilled water, with NaCl solutions of various concentrations or with a multionic Merle's solution. The solutions were administered uni- or bilaterally at volumes of 1-5 mul through chronically implanted chemitrodes. The behavior of animals and the EEG of frontal cortex, hippocampus, caudate nucleus and substantia nigra were observed. A part of the usual EEG record analysis two channels of EEG were evaluated with amplitude integrators. The main goal of the experiment was to find the optimal solvent for microinjection into the substantia nigra. So-called physiological saline solution (0-9% NaCl) was found to be most toxic and the multionic Merle's solution most suitable among the control fluids tested. The influence of "pressing effect", of pH as well as the influence of ionic concentrations of solutions tested are discussed.