Pontine Intertrigeminal Region Attenuates Sleep Apneas in Rats

Abstract

STUDY OBJECTIVES: To determine whether the pontine intertrigeminal region (ITR), with recently described anatomic connections and an effect on vagally induced reflex apnea, has an impact on spontaneous sleep apneas in rats. DESIGN: Respiration, electroencephalogram (EEG), and electromyogram (EMG) were recorded in rats with lesions of the pontine ITR and in control animals. PARTICIPANTS: 9 adult male Sprague-Dawley rats. INTERVENTIONS: Rats were implanted with EEG and EMG electrodes and were polygraphically recorded for 6 hours, and their respiration was monitored by placing each animal inside a single-chamber plethysmograph. Subsequently, a respiratory-related intertrigeminal site was identified by probing on dorsoventral tracks with 2 to 5 nL glutamate (10 nL, 10 mmol) injections from a multibarrel glass pipette. This site was then lesioned by injecting ibotenic acid (10 nL, 50 mmol) from a second pipette barrel. Animals were again recorded for 6 hours on days 2, 7, and 14 after the lesion. MEASUREMENTS AND RESULTS: ITR lesions exerted no impact on mean respiratory pattern during any sleep-wake state, compared to baseline recordings. In contrast, apnea frequency during non-rapid eye movement sleep increased following ITR lesion, more than doubling by day 14. CONCLUSIONS: This study demonstrates that a small and well-localized unilateral lesion of the ITR region in the lateral pons can increase sleep apnea expression in freely moving rats over a 2-week period. The present findings are in agreement with the general modulatory role of pontine structures in activities including respiration, heart rate, and regulation of blood pressure.