Article Figures & Data
Figures
- Fig. 1.
necdin-deficientNdntm2Stw mice have irregular respiratory rhythms with prolonged periods of central apnea.A, Sample rectified and integrated suction electrode recordings of diaphragm EMG were made from brainstem–spinal cord–diaphragm preparations isolated from E18.5 wild-type (left) and Ndntm2Stw mutant (right) mice. Recordings of 80 min duration demonstrate the regularity of respiratory discharge frequency (∼4–5 sec interspike interval) in wild-type preparations. In contrast, the respiratory frequency is very unstable in mutant preparations over time. B, Defects in respiratory rhythm are observed within the putative respiratory rhythm-generating center. Sample rectified and integrated suction electrode recordings were made from inspiratory neurons located in the pre-Bötzinger complex (PBC) and neurons within the hypoglossal (XII) nucleus in medullary slice preparations isolated from E18.5 wild-type (left) andNdntm2Stw mutant (right) mice.
- Fig. 2.
Abnormal rhythmogenesis is apparent from whole-cell patch-clamp recordings from an inspiratory neuron within the pre-Bötzinger complex. A, Rectified and integrated suction electrode recordings were made from the XII nerve roots of a wild-type E18.5 medullary slice preparation. B,Top shows whole-cell patch-clamp recording from an inspiratory neuron located within the region of the pre-Bötzinger complex. Middle shows the simultaneous recording from the XII nerve root. Bottom shows the whole-cell and nerve root recordings on a shorter time scale. Thetraces were taken from the areas demarcated in themiddle panel with horizontal bars. The rhythmic discharge fluctuates between periods of very slow rhythms (left bottom) to those in which the respiratory rhythm is similar in frequency to wild-type preparations (middle bottom). There are also occurrences of high-frequency nonrespiratory bursts (right bottom).Inset shows whole-cell and integrated nerve recordings during a single inspiratory burst.
- Fig. 3.
necdin is expressed in the fetal medulla. A, Expression of Ndn in E18.5 medullary transverse section equivalent to those used for electrophysiological studies. B, Photo of labeling in the ventrolateral medulla (pre-Bötzinger complex area approximated by dashed line). C, Higher-power photo of the pre-Bötzinger complex region.NA, Nucleus ambiguous; X, nucleus of the tenth nerve (vagus); XII, nucleus of the twelfth nerve (hypoglossal). Scale bars: A, 200 μm;B, 50 μm; C, 25 μm.
Tables
- Table 1.
Characterization of inspiratory bursts in wild-type and mutant embryonic mouse preparations
n Interval(s) Duration(s) Amplitude (mV) Coefficient of variation of burst interval Wild-type en bloc 5 3.2 ± 2.3 0.32 ± 0.09 46 ± 21 0.72 Mutant en bloc Low frequency 7 32 ± 41* 0.33 ± 0.07 51 ± 34 1.3* Medium frequency 7 3.3 ± 2.4 0.28 ± 0.05 37 ± 26 0.73 Combined average 7 8.5 ± 17.3* 0.28 ± 0.06 38 ± 27 2.0* Wild-type slice 5 3.5 ± 2.8 0.30 ± 0.08 33 ± 18 0.8 Mutant slice Low frequency 8 24 ± 37* 0.29 ± 0.08 37 ± 21 1.5* Medium frequency 8 3.8 ± 2.8 0.26 ± 0.06 27 ± 20 0.74 Combined average 8 7.1 ± 15.6* 0.27 ± 0.08 29 ± 20 2.2* The mean interburst interval, duration, and amplitude of inspiratory bursts were calculated from recordings of inspiratory motor discharge generated by brainstem–spinal cord (en bloc) and medullary slice preparations from E18.5 mice. The measurements for mutant mice were calculated separately for bouts of low- and medium-frequency bursting and put together as a combined average. Results are means ± SD; n is the number of preparations examined.
↵* p < 0.05 compared with wild type; Student's t test.
