The acute effects of amputation on peripheral trigeminal afferents in Gallus gallus var domesticus

In 10 adult Brown Leghorn hens electrical recordings were made from sensory afferent fibres in dissected nerve filaments of the trigeminal nerve innervating the lower beak. The lower beak was subjected to partial amputation using a heated blade and recordings were taken before, during and after amputation. Amputation produced a massive injury discharge which lasted from 2 to 48 sec (mean 15 sec). There were still active units present in the filament with receptive fields proximal to the site of cautery and for 90 min after amputation no abnormal activity was recorded in these units and no abnormal spontaneously active units were observed. From 90 to 270 min post-amputation single units were dissected and of the 93 rapidly adapting mechanoreceptors, 78 slowly adapting mechanoreceptors, 23 mechanothermal (polymodal) nociceptors, 7 cold and 3 warm thermoreceptors none showed any abnormal pattern of response to cutaneous stimulation. This absence of change in the peripheral neural input following amputation could provide a mechanism to explain the absence of observed pain immediately following partial beak amputation.