British Journal of Anaesthesia, 1991, Vol. 66, No. 1 88-96
© 1991 The Board of Management and Trustees of the British Journal of Anaesthesia
research-article |
BARBITURATE ALTERATION OF RESPIRATORY RHYTHM AND DRIVE IN ISOLATED BRAINSTEM-SPINAL CORD OF NEWBORN RAT: STUDIES AT NORMAL AND HYPERBARIC PRESSURE
Unit of Physiology, Faculty for Health Sciences, Ben-Gurion University of the Negev P.O. Box 653, Beer-Sheva 84 105, Israel
Department of Anaesthesia, Stanford University School of Medicine Stanford, California 94305-5123, U.S.A.
High pressure and anaesthetic agents are mutual antagonists in intact animals, but antagonism is not observed in isolated nerve cells. In order to test the hypothesis that a neural network might display pressureanaesthetic antagonism not found in simpler systems, we have examined the effects of pentobarbitone at normal pressure and at 10.1 MPa helium pressure on the rhythmic activity of medullary respiratory centres of isolated brainstem and spinal cord from 03 day old rats. Pentobarbitone 580 µmol litre1 depressed the frequency, amplitude and area of spontaneous bursts recorded from C5 reduced respiratory drive, and altered the response to trigeminal nerve root stimulation. Compression to 10.1 MPa decreased ventilatory frequency and respiratory drive, and either did not interact with or enhanced the depressant effects of pentobarbitone. Pentobarbitone and helium pressure altered the response to trigeminal nerve root stimulation in the same manner. The results are consistent with additive rather than antagonistic effects of pressure and a barbiturate on the determinants of output from the respiratory centremotor neurone pathway. Pressureanaesthetic antagonism may be a property unique to the neural circuitry which underlies awake behaviour and pressure-induced seizures, rather than reflecting a fundamental molecular-level antagonism.