Airway nociceptors activated by pro-inflammatory cytokines

The present studies evaluate whether the. vagus nerves link the lungs' immune and neural systems by transmitting information through pulmonary nociceptors. Single unit activities from pulmonary nociceptors [C fiber receptors (CFRs) and high threshold A delta fiber receptors (HTARs)] were recorded from the cervical vagus nerve in anesthetized, open-chest, and mechanically ventilated rabbits. Interleukin 1 beta was then injected into the nociceptor field (IL-1 beta, 10 mu Lg/ml, 20 mu l). Both CFRs and HTARs were stimulated by the local injection; their activities increased from 0.2 +/- 0.1 to 1.8 +/- 0.5 imp/s (n = 10; p < 0.01), and from 0.2 +/- 0.1 to 1.1 +/- 0.1 imp/s, respectively (n = 6; p < 0.0 1). These increases were greatly attenuated by simultaneous administration of (IL-1 beta with IL-1ra, a natural IL-1 receptor antagonist. The nociceptors were not stimulated by local injection of normal saline. Our data demonstrate that nociceptors can be activated by pro-inflammatory cytokines and support the hypothesis that airway nociceptors transmit immune signals front the lung to the brain. (c) 2006 Elsevier B.V. All rights reserved.