Fig 1.
Chloral hydrate anesthesia significantly increases latency of tail withdrawal from a nociceptive stimulus.
Within-subject comparison of tail withdrawal latencies to a nociceptive stimulus while unanesthetized and while subsequently anesthetized with chloral hydrate anesthesia (200mg/kg initial bolus; 150 mg/kg per hour continuous intravenous infusion). Withdrawal latencies increased significantly during chloral hydrate anesthesia in every rat tested (individual values represented in grey; average represented in black). ***p<0.0001.
Fig 2.
Heart and respiratory rate remain unchanged during nociceptive stimulation under chloral hydrate anesthesia.
(A) Within-subject comparison of respiration rate 30 seconds pre-IR stimulus and during IR stimulus averaged over 3 separate trials (individual averages are represented in grey, grand average of all animals is represented in black). (B) Within-subject comparison of heart rate 30 seconds pre-IR stimulus and during IR stimulus averaged over 3 separate trials (individual averages are represented in grey, grand average of all animals is represented in black).
Fig 3.
Heart and respiratory rate remain unchanged with or without tail flick response during nociceptive stimulation under chloral hydrate anesthesia.
(A) Within-subject comparison of instantaneous (cycle-by-cycle) respiration rate (left) and heart rate (right) 30 seconds pre-IR stimulus (in black) and during IR stimulus (in red) for a single trial. The ramped thermal nociceptive stimulation was terminated at the arrowhead (14.5 s) due to a tail flick reaction. (B) Within-subject comparison of instantaneous (cycle-by-cycle) respiration rate (left) and heart rate (right) 30 seconds pre-IR stimulus (in black) and during IR stimulus (in red) for a single trial. The ramped thermal nociceptive stimulation was continued throughout the 30 s trial since no withdrawal occurred (C) Instantaneous respiration rate (left) and heart rate (right) during IR exposure for all trials (3 trials per animal). Each animal is denoted by a separate colour. (D) Linear fits of the instantaneous respiration rate (left) and heart rate (right) for individual trials during IR exposure, with each animal denoted by a separate colour, as in C. In no case was there a significant positive linear fit.