Cardiorespiratory and sleep-wake behavior in developing swine: kappa-opioid influence.

Effects of specific kappa-opioid antagonism with norbinaltorphimine (NorBNI) on sleep-wake state, blood pressure and heart rate, and on diaphragmatic and posterior cricoarytenoid electromyographic activities were assessed in 3 to 13 and 23 to 33 day-old, chronically instrumented, unanesthetized piglets. Preliminary experiments established the pharmacodynamics and dose-response for NorBNI. In the main study, each piglet was studied twice daily, once before and once after 3.7 mg kg-1 NorBNI iv, for up to five consecutive days. During each study session, piglets underwent 10 min trials with 21% O2 in 79% N2 followed by 10% O2 in 90% N2 while lying in a sling within a plexiglass box. Sleep-wake distribution and cardiorespiratory functions matured with age. NorBNI produced a modest increase of arterial pressure and heart rate in the older group only, and altered neither state nor respiration at either age. These results suggest that, in the developing piglet model, the kappa-opioid system influences neither breathing nor state, but modulates cardiovascular regulation to a modest degree and later in ontogeny.