Abstract
Endorphins are endogenous polypeptides with morphine-like activity which are widely distributed in the central nervous system and bind to opiate receptors. They presumably function as inhibitory neurotransmitters in pain pathways. We tested the hypothesis that endorphins modified the respiratory response to asphyxia in newborn rabbit pups (3-5 days of age). Pups from the sane litter were injected I.P. with either 1 ml saline or 1 ml (0.4mg) naloxone, a specific endorphin antagonist. Five minutes later asphyxia was produced by tracheal occlusion and maintained until gasping resumed after primary apnea. Four occlusions were done on each pup and 3 minutes allowed for recovery between occlusions. The time to primary apnea increased by 20% from 44.2±1.5 (S.E.) sec in saline pups to 52.9±1.9 sec in naloxone pups (p<.001) while the duration of primary apnea decreased by 60% (45.5±11.1 vs 18.3±2.0 sec) (p=.01). The tracheal pressure achieved during the first gasp following primary apnea was identical in saline and naioxone pups (54.2±2.7 vs 54.3±2.5 cm H2O). Naloxone acts by competitive blockada of opiate (endorphin) receptors. These data therefore provide evidence that endorphins modify the respiratory response to asphyxia by decreasing the frequency of respiratory center discharge but do not appear to decrease the amplitude of the respiratory center output at the time of the first gasp.
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Chernick, V., Madansky, D. & Lawson, E. EVIDENCE THAT ENDORPHIN (S) MODIFY THE RESPIRATORY RESPONSE TO NEONATAL ASPHYXIA. Pediatr Res 11, 532 (1977). https://doi.org/10.1203/00006450-197704000-00972
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DOI: https://doi.org/10.1203/00006450-197704000-00972