Large dorsal horn neurons which receive inputs from numerous substance P-like immunoreactive axon terminals in the laminae I and II of the chicken spinal cord

Comparative Physiology of Nociception and Pain

“…Both Adelta and C fibers have been identified innervating the beak, nasal, and buccal mucosa and the legs of chickens (40), and these respond with comparable properties to mammalian nociceptors, with evidence for sensitization (32,40). Afferents project to the avian brain stem, ascending to the presumed primary pain processing centers in the forebrain (32,159). A range of analgesic drugs are administered to ameliorate pain or nociception in birds (95), and thus there is a high evolutionary conservation of receptors for drugs such as opioids (30,65,89).…”

Methods of Pain Assessment in Chicks as a Model

“…In mammals, the dorsal horn of the spinal cord has 10 layers, Both cell size and spread can be distinguished, while hens possess 6 layers [22]. The pain signal is conveyed to the dorsal horn's layer I and external layer II through primary afferent nerve fibers Aδ and C [26] .In birds, the neuron distribution is similar to that in monkeys and cats of nociceptive spinothalamic tract cells [26], nerves get feedback from substance P -having nerve terminals, which also tend to achieve a major part in bird pain pathways [25]. One study found melatonin can also be involved in the transmission of sensory signals, like pain neurotransmission [26].…”

“…Furthermore, eicosanoids and prostaglandin E1 and E2 sensitize thermal and mechanical stimulation of the small-diameter sensory nerve fibers. Substance P tends to be an essential mediator of inflammation Components, and its discharge leads to vasodilation in the circulatory system and additional excitation of the C fiber peripherally [25]. Exposure to prostaglandin E2 in chick sensory nerves causes a dose-dependent rise in the production of substance P over inward Ca influx [24].…”

<b>Indicadores de bem-estar de linhagens de poedeiras comerciais leves alojadas em cinco densidades no sistema convencional de produção de ovos</b>

“…Estudos anatômicos e bioquímicos revelam que a fisiologia da dor nas diferentes espécies animais é semelhante (REINER et al, 1984;BRENNER et al, 1994;ZHAI;ATSUMI, 1997).…”