Activation of hypothalamic arcuate but not paraventricular neurons following carotid body chemoreceptor stimulation in the rat.

The effect of carotid body chemoreceptor stimulation on 292 neurons in midline hypothalamic nuclei has been examined electrophysiologically in ethyl carbamate/sodium pentobarbitone anaesthetized rats. Experiments demonstrated that specific stimulation of carotid body chemoreceptors activates a small group (16) of neurons in the mediobasal hypothalamic arcuate nucleus, but has no effect on neurons (157) in the hypothalamic paraventricular nucleus or the anterior hypothalamus. Of 16 arcuate neurons activated by the stimulus, six projected to the median eminence and three projected to the dorsal medulla, as defined by antidromic invasion. Three of the neurons activated from the carotid body also showed a resting discharge that was linked with ventilation rate, suggesting that the arcuate nucleus may have some involvement with respiratory processing. The activation of neurons projecting to the median eminence implies that the release of adenohypophyseal hormones may also be influenced by carotid body chemoreceptors.