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. 2022 Aug 31;12(17):2257. doi: 10.3390/ani12172257

Table 1.

Phases and characteristics of the nociceptive pathway caused by bite injuries in dogs.

Phases Description Main Involved Structures Chemical Mediators References
1. Transduction Transforming harmful stimuli into an electrical impulse (action potential)
  • ∘

    Nociceptors in the skin, muscles, bones, and viscera.

  • ∘

    Ionic channels (TRP)

 5-HT, BK, H, H+, K+, LT, NT, NY, PAG, PG, ROS, TNF-α, TX [50,53,54,55,56,57,58,59]
2. Transmission Electrical impulse travels to the DRG and spinal cord interneurons
  • ∘

    Aδ and C free nerves

  • ∘

    Spinal cord

  • ∘

    Laminae I, II, and V

 GLU, SP, CGRP [57,58,59,60,61]
3. Modulation Facilitate or inhibit nociceptive transmission
  • ∘

    Dorsal horn of the spinal cord

  • ∘

    Descending pathways

  • ∘

    NMDAr, AMPAr

 ASP, BK, CA, CGRP, EOP, IL, LT, PC, PG, SP [54,61,62,63]
4. Projection Carry nociceptive inputs from the spinal cord to supraspinal structures
  • ∘

    Spinal cord, brainstem, thalamus, hypothalamus, amygdala

  • ∘

    Ascending pathways (spinothalamic tract)

 GLU, SP [62,63]
5. Perception Integration of the conscious recognition of pain
  • ∘

    Somatosensory cortex

 GLU, SP [51,55]

AMPAr: AMPA receptor; ASP: aspartate; BK: bradykinin; CA: catecholamines; CGRP: calcitonin-gene-related peptide; DRG: dorsal root ganglion; EOP: endogenous opioid peptides; GLU: glutamate; H: histamine; H+: hydrogen; IL: interleukin; K+: potassium; LT: leukotrienes; NMDAr: NMDA receptor; NT: neurotrophins; PAF: platelet-activating factor; PC: prostacyclin; PG: prostaglandin; ROS: free radicals; SP: substance P; TNFα: tumoral necrosis factor; TRP: transient receptor potential; TX: thromboxane; 5-HT: serotonin.