title: Dose-response characteristics of intravenous ketamine on dissociative stereotypy, locomotion, sensorimotor gating, and nociception in male Sprague-Dawley rats.
abstract: Clinicians administer subanesthetic intravenous (IV) ketamine infusions for treatment of refractory depression, chronic pain, and post-traumatic stress disorder in humans. However, ketamine is administered via the subcutaneous (SC) or intraperitoneal (IP) routes to rodents in most pre-clinical research, which may limit translational application. The present study characterized the dose-response of a subanesthetic IV ketamine bolus (2 and 5mg/kg) and 1-h infusion (5, 10, and 20mg/kg/h) on dissociative stereotypy, locomotion, sensorimotor gating, and thermal nociception in male Sprague-Dawley rats. The secondary aim was to measure ketamine and norketamine plasma concentrations following IV ketamine bolus at 1, 20, and 50min and at the conclusion of the 1-h infusion using liquid chromatography/mass spectrometry. The results showed that ketamine bolus and infusions produced dose-dependent dissociative stereotypy. Bolus (2 and 5mg/kg) and 20mg/kg/h infusion increased locomotor activity while 5mg/kg/h infusion decreased locomotor activity. Both 10 and 20mg/kg/h infusions reduced the acoustic startle reflex, while 5mg/kg bolus and 20mg/kg/h infusion impaired pre-pulse inhibition. Ketamine 5mg/kg bolus and the 10 and 20mg/kg/h infusions induced significant and prolonged antinociception to the hotplate test. Plasma concentrations of ketamine decreased quickly after bolus while norketamine levels increased from 1 to 20min and plateaued from 20 to 50min. The peak ketamine plasma concentrations [ng/ml] were similar between 5mg/kg bolus [4100] vs. 20mg/kg/h infusion [3900], and 2mg/kg bolus [1700] vs. 10mg/kg/h infusion [1500]. These results support the findings from previous ketamine injection studies and further validate the feasibility of administering subanesthetic doses of IV ketamine infusion to rats for neuropharmacological studies.
authors.affiliation: Daniel K. Inouye Graduate School of Nursing, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Kennett D
authors.initials: KD
authors.lastname: Radford
authors.affiliation: Department of Psychiatry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; The Center for Study of Traumatic Stress, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Thomas Y
authors.initials: TY
authors.lastname: Park
authors.affiliation: Department of Psychiatry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Department of Acupuncture, Moxibustion and Acupoint, College of Korean Medicine, Daegu Haany University, Daegu 42158, Republic of Korea.
authors.forename: Bong Hyo
authors.initials: BH
authors.lastname: Lee
authors.affiliation: Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Moran
authors.affiliation: Daniel K. Inouye Graduate School of Nursing, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Osborne
authors.affiliation: Daniel K. Inouye Graduate School of Nursing, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Department of Psychiatry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; The Center for Study of Traumatic Stress, Uniformed Services University of the Health Sciences, Bethesda, MD, USA. Electronic address: kwang.choi@usuhs.edu.
authors.forename: Kwang H
authors.initials: KH
authors.lastname: Choi
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007649:Ketamine / Q000097:blood / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055139:Sensory Gating / Q000187:drug effects*; D013239:Stereotyped Behavior / Q000187:drug effects*
chemical_list: D000700:Analgesics; D007649:Ketamine
keywords: Antinociception; Dissociative stereotypy; Intravenous; Ketamine; Locomotor activity; Rat; Sensorimotor gating