Research ReportsAcute intrathecal administration of quipazine elicits air-stepping behaviorSwann-Thomsen, Hillary E.a; Viall, Derek D.b; Brumley, Michele R.c Author Information aIdaho Center for Health Research, Idaho State University bDepartment of Biological Sciences, University of Idaho cDepartment of Psychology, Idaho State University, Meridian, Idaho, USA Received 7 April 2020 Accepted as revised 6 October 2020 Correspondence to Hillary E. Swann-Thomsen, PhD, Idaho Center for Health Research, Idaho State University, 1311 E Central Drive, Meridian, ID 83642, USA, E-mail: [email protected] Behavioural Pharmacology: June 2021 - Volume 32 - Issue 4 - p 259-264 doi: 10.1097/FBP.0000000000000608 Buy Metrics Abstract Serotonin plays a pivotal role in the initiation and modulation of locomotor behavior in the intact animal, as well as following spinal cord injury. Quipazine, a serotonin 2 receptor agonist, has been used successfully to initiate and restore motor behavior in rodents. Although evidence suggests that the effects of quipazine are spinally mediated, it is unclear whether intrathecal (IT) quipazine administration alone is enough to activate locomotor-like activity or whether additional stimulation is needed. Thus, the current study examined the effects of IT administration of quipazine in postnatal day 1 rats in two separate experiments. In experiment 1, quipazine (0.1, 0.3, or 1.0 mg/kg) was dissolved in saline and administered via IT injection to the thoracolumbar cord. There was no significant effect of drug on hindlimb alternating stepping. In experiment 2, quipazine (0.3 or 1.0 mg/kg) was dissolved in a polysorbate 80-saline solution (Tween 80) and administered via IT injection. Polysorbate 80 was used to disrupt the blood-brain barrier to facilitate absorption of quipazine. The injection was followed by tail pinch 5 minutes post-injection. A significant increase in the percentage of hindlimb alternating steps was found in subjects treated with 0.3 mg/kg quipazine, suggesting that IT quipazine when combined with sensory stimulation to the spinal cord, facilitates locomotor-like behavior. These findings indicate that dissolving the drug in polysorbate 80 rather than saline may heighten the effects of IT quipazine. Collectively, this study provides clarification on the role of quipazine in evoking spinally-mediated locomotor behavior. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.