title: Mouse current vocalization threshold measured with a neurospecific nociception assay: the effect of sex, morphine, and isoflurane.
abstract: Sine-wave electrical stimulation at frequencies 2000, 250, and 5Hz to respectively evaluate Aβ, Aδ, and C sensory neurons has recently been added to the armamentarium used to evaluate sensory neurons. We developed an automated nociception assay using sine-wave stimulation methodology to determine current vocalization threshold in response to 2000, 250, and 5Hz and examine the effects of sex, analgesics, and anesthetics in mice. At baseline, males had significantly higher mean current vocalization thresholds compared with female mice at 2000, 250, and 5Hz (p≤0.019). By 1h after intrathecal injections of morphine there were significant increases in current vocalization threshold percent changes from baseline that varied with doses (p=0.0001) and frequency used (p<0.0001). Specifically, with increasing doses of morphine, there were significantly greater increases in current vocalization threshold percent changes from baseline in response to 5Hz compared with 250 and 2000Hz stimulation in a significantly ordered pattern: 5Hz>250Hz (p<0.0001) and 250Hz>2000Hz (p=0.0002). Forty-five minutes after exposure, there were no effects of isoflurane on current vocalization thresholds at any frequency. Therefore, our findings suggest that this automated nociception assay using sine-wave stimulation in mice, can be valuable for measurements of the effects of sex, opioids, and anesthetics on the response to electrical stimuli that preferentially stimulate Aβ, Aδ, and C-sensory fibers in vivo. This investigation suggests the validation of this assay and supports its use to examine mechanisms of nociception in mice.
authors.affiliation: The Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Medical Center, 111 Michigan Avenue, Washington, DC 20010, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Spornick
authors.forename: Virginia
authors.initials: V
authors.lastname: Guptill
authors.forename: Deloris
authors.initials: D
authors.lastname: Koziol
authors.forename: Robert
authors.initials: R
authors.lastname: Wesley
authors.forename: Julia
authors.initials: J
authors.lastname: Finkel
authors.forename: Zenaide M N
authors.initials: ZM
authors.lastname: Quezado
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation / Q000009:adverse effects* / Q000379:methods; D005260:Female; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D059225:Nociception / Q000187:drug effects* / Q000502:physiology; D010147:Pain Measurement / Q000295:instrumentation / Q000379:methods; D011984:Sensory Receptor Cells / Q000187:drug effects* / Q000502:physiology; D012727:Sex Characteristics; D014828:Vocalization, Animal / Q000187:drug effects* / Q000502:physiology
chemical_list: D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D009020:Morphine; D007530:Isoflurane