The influence of the menstrual cycle on upper airway resistance and breathing during sleep.

STUDY OBJECTIVE: Female hormones, specifically progesterone, that peak in the luteal phase may play a significant role in protecting premenopausal women from sleep-disordered breathing. The influence of female hormones on upper airway resistance during sleep was investigated during the follicular and luteal phases of normal menstrual cycles. SETTING: Hospital-based sleep laboratory. DESIGN AND PARTICIPANTS: Healthy women with verified ovulatory cycles and without sleep complaints were recruited into the study. Sleep and upper airway resistance data (mean +/- SD) were collected on 2 nights from 11 women (21-49 years of age [28 +/- 9 years], body mass index of 22.8 +/- 3.6 kg/m2), once during the follicular phase (day 6-11) and once in the luteal phase (day 19-23) in random order. MEASUREMENTS AND RESULTS: Nasal resistance, standardized to a flow rate of 0.3 L/second, measured using posterior active rhinomanometry immediately prior to the sleep study, did not differ between the 2 phases. The respiratory disturbance index tended to be higher in the follicular phase than in the luteal phase and was above 5 per hour for 3 women in the follicular phase. Upper airway resistance, controlled for flow rate and body position, was calculated for 50 random breaths during wakefulness, stage 1, stage 2, slow-wave, and rapid eye movement sleep. During wake and stage 2 sleep, upper airway resistance was significantly higher in the follicular phase than in the luteal phase, as was the overall upper airway resistance combined for wake and across all sleep stages. Combining data from the 2 nights, compared to wake, upper airway resistance increased in stage 2, slow-wave, and rapid eye movement sleep. CONCLUSIONS: Within the menstrual cycle, upper airway resistance is lower in the luteal compared with the follicular phase.

Expression of alpha(2)-adrenergic receptor subtypes in prenatal rat spinal cord.

The results of molecular cloning have revealed three subtypes of the alpha(2)-adrenergic receptors (alpha(2) AR) that have been defined alpha(2)C10 (alpha(2A)), alpha(2)C2 (alpha(2B)) and alpha(2)C4 (alpha(2C)). The differential expression of alpha(2) AR subtypes is affected by developmental factors in rat submandibular gland, lung and brain. In the spinal cord of postnatal and adult rats, alpha(2A) and alpha(2C) AR subtypes are expressed and appear to mediate pain perception. However, the relative expression of alpha(2) AR subtypes in the prenatal spinal cord is unknown. In the present study subtype-specific antibodies and reverse transcription-polymerase chain reaction (RT-PCR) were used to determine the expression and localization of the alpha(2) AR subtypes in sections of embryonic day 14 rat spinal cords and primary cultures of cells isolated from these cords. Spinal cords were removed from day 14 embryos, and were sectioned or used for the preparation of cell cultures. After 9 days in culture, neurons were examined by immunofluorescence microscopy or used for preparation of total RNA. In both intact spinal cords and isolated cells, positive immunoreactivity was detected with antibodies against alpha(2A) and alpha(2B) subtypes, but not with antibodies against the alpha(2C) subtype. Using a dual-labeling approach, anti-alpha(2A) and anti-alpha(2B) immunoreactivity was present on the same population of neurons. RT-PCR results were consistent with immunofluorescence studies, and showed that mRNA encoding the alpha(2A) and alpha(2B) subtypes was present in total RNA prepared from primary cultures of rat spinal cord neurons. In contrast to spinal cords of postnatal or adult rats that express alpha(2A) and alpha(2C) AR subtypes on different neurons, prenatal spinal cords contain alpha(2A) and alpha(2B) AR subtypes, and these two subtypes appear to be co-expressed in the same cells.

Role of Nova-1 in regulating alpha2N, a novel glycine receptor splice variant, in developing spinal cord neurons.

Inhibitory glycine receptor (GlyR) subunits undergo developmental regulation, but the molecular mechanisms of GlyR regulation in developing neurons are little understood. Using RT-PCR, we investigated the regulation of GlyR alpha-subunit splice forms during the development of the spinal cord of the rat. Experiments to compare the amounts of mRNA for two known splice variants of the GlyR alpha2 subunit, alpha2A and alpha2B, in the developing rat spinal cord revealed the presence of an additional, novel variant that lacked any exon 3, herein named "alpha2N." Examination of the RNA from spinal cords of different-aged rats showed a dramatic down-regulation of alpha2N during prenatal development: alpha2N mRNA formed a significant portion of the alpha2 subunit pool at E14, but its relative level was reduced by 85% by birth and was undetectable in adults. Two proteins previously implicated in regulating the splicing of GlyR alpha2 pre-mRNA, the neurooncological ventral antigen-1 (Nova-1) and the brain isoform of the polypyrimidine tract binding protein (brPTB), underwent small changes over the same period that did not correlate directly with the changes in the level of alpha2N, calling into question their involvement in the developmental regulation of alpha2N. However, treatment of spinal cord neurons in culture with antisense oligonucleotides designed selectively to knock down one of three Nova-1 variants significantly altered the relative level of GlyR alpha2N, showing that Nova-1 isoforms can regulate GlyR alpha2 pre-mRNA splicing in developing neurons. These results provide evidence for a novel splice variant of the GlyR alpha2 subunit that undergoes dramatic developmental regulation, reveal the expression profiles of Nova-1 and brPTB in the developing spinal cord, and suggest that Nova-1 plays a role in regulating GlyR alpha2N in developing neurons.