Pontine intertrigeminal region attenuates sleep apneas in rats.

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.