Angiotensin Ii-Induced Drinking Behavior As A Method To Verify Cannula Placement Into The Cerebral Ventricles Of Mice: An Evaluation Of Its Accuracy

Background: Intracerebroventricular (icv) injections are frequently used in neuroscience research. In addition to histological verification of the injection sites, administration of angiotensin II (ANG II) is often used to verify the injection placements. ANG II is a peptide hormone exerting dipsogenic effects, i.e., it increases drinking, when administered into the cerebral ventricles. This study investigated the accuracy of ANG II-induced drinking as a method to verify icv cannula placements.Methods: Male C57BL/6J mice were implanted with cannulas in the lateral ventricle. Then, icv injections of ANG II were performed and drinking behavior of the mice was recorded. After the behavioral experiment, we histologically verified the cannula placements using dye injections. Based on this, mice were grouped in "icv" and "misplaced". The effects of icv and misplaced ANG II injections on drinking behavior were used to evaluate the accuracy of ANG II-induced drinking as a method to verify icv cannula placements.Results: In general, ANG II injections in mice with histologically verified icv cannula placements induced robust drinking responses, while misplaced injections did not. However, there were exceptions in both groups. In about one third of the mice, icv ANG II did not induce drinking or misplaced ANG II injections induced drinking, respectively.Conclusion: These data demonstrated that ANG II-induced drinking is not a perfectly accurate method to verify icv cannula placements in mice. Therefore, we recommend to not base the decision of in- or excluding experimental subjects solely on this method, but also to histologically verify cannula placements.