Fig. 1

Pivotal spinal cord anatomy for nociception, puritoception and perception of pain and itch. Lamina of the spinal cord dorsal horn are indicated by roman numerals. The superficial dorsal horn is the main target for nociceptive and prurioceptive afferents whereas the deeper laminae receive light touch, proprioception and vibration afferents. The other neuronal constituents of the dorsal horn include local and descending axons which modulate sensory transmission. The projection neurons for nociception travel via the spinocervicothalamic (via the lateral cervical nucleus) and spinothalamic tract to the thalamus and then onto the brain’s pain processing centres that lead to conscious and unconscious pain and itch perceptions, and the emotions, and actions that these evoke. There is much overlap between neural circuitry of nociception, pruritoception, pain and prurititis because both are nocifensive and it is postulated that itch evolved from simple nociception to protect against small clinging threats [12]. However in carnivores the specific pathway for ascending pruritoceptive information in the carnivore has not been investigated. The brain modulates as well as receives information about nociception and itch and can inhibit or potentiate impulses. Scratching blocks the perception of itch [32]. Inhibition of the itch signal is mediated by dorsal horn inhibitory interneurons which are thought to be influenced by inhibitory noradrenergic and serotoninergic neurons descending from the diencephalon, raphe nuclei and midbrain periaqueductal grey mater (locus ceruleus) via the rostral ventral medulla [44]. These descending fibres are within the dorsolateral funiculus lateral to the dorsal horn