Journal of Applied Physiology, Vol 69, Issue 6 2233-2238, Copyright © 1990 by American Physiological Society
Local application of somatostatin in the rat ventrolateral brain medulla induces apnea
Z. B. Chen, T. Hedner and J. Hedner
Department of Pharmacology and Clinical Pharmacology, University of Goteborg, Sweden.
Local injections of the tetradecapeptide somatostatin (SOM) into the brain
stem region were performed in anesthetized and decerebrate rats. SOM
administration (0.6-1.8 nmol) into the nucleus paragigantocellularis and
the nucleus reticularis lateralis of the ventrolateral medulla oblongata
induced ventilatory depression and apnea. The occurrence of apnea was dose
dependent and attributed to the anesthetic depth, and it was seen within
60-240 s after injection. In anesthetized rats the apnea was seen as a
termination or a continuous decrease in tidal volume while respiratory
frequency remained unaltered. SOM-induced apnea was caused by depression of
central inspiratory drive. SOM injections into the dorsal medulla were
ineffective in eliciting apnea, although a ventilatory depression but no
apnea was induced in the awake unanesthetized state. In addition to its
effect on basal ventilation, SOM administration in the ventrolateral
medulla resulted in a blunted ventilatory response to hypoxic and
hypercapnic stimuli in anesthetized rats. We conclude that SOM has potent
inhibitory effects on respiration that are specifically located in the
nucleus paragigantocellularis and the nucleus reticularis lateralis.
