title: Characterization of the head-twitch response induced by hallucinogens in mice: detection of the behavior based on the dynamics of head movement.
abstract: BACKGROUND
  The head-twitch response (HTR) is a rapid side-to-side rotational head movement that occurs in rats and mice after administration of serotonergic hallucinogens and other 5-HT2A agonists. The HTR is widely used as a behavioral assay for 5-HT2A activation and to probe for interactions between the 5-HT2A receptor and other transmitter systems.
  
  
  OBJECTIVE
  High-speed video recordings were used to analyze the head movement that occurs during head twitches in C57BL/6J mice. Experiments were also conducted in C57BL/6J mice to determine whether a head-mounted magnet and a magnetometer coil could be used to detect the HTR induced by serotonergic hallucinations based on the dynamics of the response.
  
  
  RESULTS
  Head movement during the HTR was highly rhythmic and occurred within a specific frequency range (mean head movement frequency of 90.3 Hz). Head twitches produced wave-like oscillations of magnetometer coil voltage that matched the frequency of head movement during the response. The magnetometer coil detected the HTR induced by the serotonergic hallucinogens 2,5-dimethoxy-4-iodoamphetamine (DOI; 0.25, 0.5, and 1.0 mg/kg, i.p.) and lysergic acid diethylamide (LSD; 0.05, 0.1, 0.2, and 0.4 mg/kg, i.p.) with extremely high sensitivity and specificity. Magnetometer coil recordings demonstrated that the non-hallucinogenic compounds (+)-amphetamine (2.5 and 5.0 mg/kg, i.p.) and lisuride (0.8, 1.6, and 3.2 mg/kg, i.p.) did not induce the HTR.
  
  
  CONCLUSIONS
  These studies confirm that a magnetometer coil can be used to detect the HTR induced by hallucinogens. The use of magnetometer-based HTR detection provides a high-throughput, semi-automated assay for this behavior, and offers several advantages over traditional assessment methods.
authors: Department of Psychiatry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0804, USA. ahalbers@ucsd.edu
authors: Adam L
authors: AL
authors: Halberstadt
authors: Mark A
authors: MA
authors: Geyer
mesh_terms: D000661:Amphetamine / Q000008:administration & dosage / Q000494:pharmacology; D000662:Amphetamines / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D006213:Hallucinogens / Q000008:administration & dosage / Q000494:pharmacology*; D019416:Head Movements / Q000187:drug effects; D057166:High-Throughput Screening Assays / Q000379:methods; D008090:Lisuride / Q000008:administration & dosage / Q000494:pharmacology; D008238:Lysergic Acid Diethylamide / Q000008:administration & dosage / Q000494:pharmacology*; D060306:Magnetometry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012680:Sensitivity and Specificity; D014741:Video Recording
chemical_list: D000662:Amphetamines; D006213:Hallucinogens; D008238:Lysergic Acid Diethylamide; D000661:Amphetamine; D008090:Lisuride; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine