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Learning to cope with biting flies: rapid NMDA-mediated acquisition of conditioned analgesia
M Kavaliers1, D D Colwell, E Choleris
1Department of Psychology, University of Western Ontario, London, Canada. kavalier@julian.uwo.ca
Abstract:
A 30-min exposure to intact biting flies (stable flies) induced an opioid-mediated analgesia in fly-naive male deer mice, whereas exposure to either altered biting flies whose biting mouthparts were removed or nonbiting house flies had no significant effects. However, mice that were previously exposed to intact stable flies for 30 min exhibited significant analgesia when exposed 24-168 hr later to stable flies whose biting parts were removed, but not to nonbiting house flies. Administration of the specific N-methyl-D-aspartate (NMDA) antagonist NPC 12626 to fly-naive mice before exposure to intact flies, although not significantly reducing the analgesic response, blocked the subsequent conditioned analgesia. Naloxone, which blocked the intact biting fly-induced analgesia, did not alter the acquisition of the conditioned analgesic response to the altered stable flies. This demonstrates an NMDA-mediated acquisition of conditioned analgesia to a natural aversive stimulus.
Insights
Biting flies trigger pain relief (analgesia) in mice through opioid pathways. Prior exposure to biting flies creates a conditioned pain relief response, mediated by N-methyl-D-aspartate (NMDA) receptors.
Area of Science:
- Neuroscience
- Animal Behavior
- Immunology
Background:
- Insect bites can elicit complex physiological responses in mammals.
- Pain perception and modulation involve intricate neural pathways, including opioid and NMDA receptor systems.
Purpose of the Study:
- To investigate the mechanisms of analgesia induced by biting flies in deer mice.
- To explore the role of opioid and N-methyl-D-aspartate (NMDA) receptors in both immediate and conditioned analgesic responses to insect bites.
Main Methods:
- Exposure of male deer mice to intact stable flies, altered stable flies (mouthparts removed), and nonbiting house flies.
- Administration of naloxone (opioid antagonist) and NPC 12626 (NMDA antagonist) to assess receptor involvement.
- Testing for immediate analgesia and conditioned analgesia upon subsequent exposure to altered flies.
Main Results:
- A 30-minute exposure to intact stable flies induced opioid-mediated analgesia.
- Previous exposure to intact flies resulted in conditioned analgesia to altered stable flies, indicating a learned response.
- NMDA receptor blockade prevented the acquisition of conditioned analgesia, while opioid blockade did not affect it.
Conclusions:
- The study demonstrates an opioid-mediated immediate analgesic response to intact biting flies.
- A learned, N-methyl-D-aspartate (NMDA)-dependent conditioned analgesic response can be acquired following exposure to a natural aversive stimulus (biting flies).
- These findings highlight the complex interplay between sensory input, learning, and pain modulation in response to insect-induced stress.
