Abstract
The contribution of the central nervous system(CNS) in newborns to inotropic and chronotropic responses induced by G-trophanthin(G-S) is unknown and was the subject of this investigation. Five reflexlc lambs, 2-15 days of age, in which the cerebral circulation had been isolated were subjected to (1)cerebral, and then, (2) systemic infusions of G-S (80 ug/Kg). Cerebral perfusion pressure(arterial - intracranial pressure), flow, and EEG, systemic pressure, left ventricular contractility(LVC) during pacing, and EKG were continuously monitored while in both circulations blood gases and temperature were kept close to normal. The infusion of G-S into the cerebral circulation was not associated with significant changes in LVC, rate, or rhythm. Systemic infusion of G-S produced a significant increase in LVC (p .01) evidenced by an increase in DP/DT/P. Chronotropic disturbances developed in 4/5 animals. CNS perfusion and its viability was interrupted, LVC transiently increasing(p .001). All lambs developed arrhythmias when the G-S infusion was increased. It is concluded that CNS influences are not essential for inotropic and chronotropic responses to G-S in the lamb.
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