Vol. 278, Issue 4, R973-R979, April 2000
Carotid and cardiopulmonary chemoreceptor activity increases
hippocampal theta rhythm in conscious rabbits
Ying-Hui
Yu and
W. W.
Blessing
Centre for Neuroscience, Departments of Medicine and Physiology,
Flinders University, Bedford Park 5042 SA, Australia
We have examined whether activation of carotid artery
chemoreceptors causes alerting in conscious rabbits. Injection of
phenylbiguanide (a 5-hydroxytryptamine3-receptor agonist)
into the common carotid artery of conscious rabbits increased the
proportion of theta rhythm in the hippocampal EEG, commencing in the
first 5-s epoch after the injection. Intravenous injection of
phenylbiguanide also increased the proportion of theta rhythm in the
hippocampal electroencephalogram (EEG), but the onset of the change was
not until the second 5-s epoch following injection. Injection of Ringer solution, either into the common carotid artery or into the marginal ear vein, did not affect the hippocampal EEG. Results suggest that
phenylbiguanide-mediated activation of carotid and cardiopulmonary chemoreceptor afferents alerts the animal, as assessed by induction of
theta rhythm in the hippocampal EEG. This alerting response presumably
reflects the action of neural inputs that enter the brain with the
carotid sinus nerve at the level of the medulla oblongata.
electroencephalogram; arousal/orientation response; carotid body; carotid sinus nerve; sudden infant death syndrome; 5-hydroxytryptamine3 receptors.
