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Didgeridoo playing as alternative treatment for obstructive sleep apnoea syndrome: randomised controlled trial

BMJ 2006; 332 doi: (Published 02 February 2006) Cite this as: BMJ 2006;332:266

Didgeridoo and vagal stimulation.

The above website provides both listening and learning instructions
on didgeridoo playing. Other related websites refer to the abilty of
the instrument to influence vagal involvement. An online search for
'digeridoo vagus' will provide a wide range of associated information in
that regard.

In my first response, I stated that a theoretical model of sleep and
arousal which I have constructed, suggests that
the low Hz. vibrations of the didgeridoo are conducted downward along the
efferent vagal pathway, and in common with the Pasche spoon, the OMMMM
utterances and the 'Tibetan stomach singing', they result in reduction of
abdominal afferential vagal signalling back to the nucleus tractus
solitarius (NTS) in the brainstem.The overall result is that SNS input is
decreased, and in the case of insomnia this facilitates sleep onset.

Now may be the appropriate time to provide additional and more
detailed information in that regard. The following has been copied
directly from the relevant section of the model's text:

Research conducted by Hawthorn et al (1988) on the ferret showed that
electrical stimulation of the abdominal afferent vagus nerve caused the
release of increased levels of vasopressin (AVP) but not oxytocin (OT) in
the NTS. Independent of their individual roles peripherally, central
involvement of both AVP and OT as regulatory neurotransmitters of the
autonomic system was clearly demonstrated by Landgraf et al.(1990) using
anaesthetized rats. Electrical stimulation of the ipsilateral
paraventricular nucleus (PVN) of the hypothalamus, resulted in a 5-fold
increased level of OT and AVP, recovered and measured in a push-pull
perfusate of the NTS and dorsal motor vagus (DMV) area. After stimulation,
the peptides were found to return to the level of controls. An osmotic
stimulus failed to increase AVP and OT levels in the NTS/DMV perfusate.
The authors concluded that their results were consistent with the view
that both peptides are centrally involved as neurotransmitters in
autonomic regulation.

Central oxytocinergic neurons had also been hypothesized to influence
gastric motility and secretion by increasing the excitability of central
vagal neurons in the NTS and the nucleus of the DMV. Support for this
hypothesis was evidenced in a study using the rat by McCann and Rogers
(1990). In the following year Nordmann and Steunkel (1991) demonstrated
that Na+ acts directly in releasing AVP from rat isolated neurohypophysial
nerve endings. The secretory elevation was dose dependently related to Na+
and could occur in the absence of Ca++. The authors concluded that Na+ per
se may be an intrinsic regulator of basal neurosecretion.

A study by Raggenbass et al. (1992) carried the work forward by
elucidating the roles played by both Na+ and Ca++ in the regulation of
vagal neurotransmission in the brainstem. These investigators studied the
effect of OT on brainstem slices of vagal neurons of the rat. OT induced
current was concluded to be inward and voltage dependent since its
magnitude moved from the resting potential toward less negative
potentials. Regulation of the OT induced current in response to membrane
potential suggested that OT acts by effecting opening of voltage dependent
channels, which can exist in either of two states or closed.
Extracelluar calcium (Ca++) in lowered concentration enhanced the OT
response, while raising the Ca++ concentration reduced it. Partial
replacement of ECF Na+ was shown to reversibly attenuate or suppress the
OT current. The authors concluded that OT increases the excitability of
vagal neurons by generating a voltage-gated current, which is modulated by
divalent cations and carried by Na+.

More recently, a paper dealing with peptides as neurotransmitters in
vascular autonomic neurons (Morris,1995) stated that neuropeptides are
present in the majority of autonomic neurons projecting to blood vessels,
where they work in conjunction with non- peptide transmitters and
sometimes with other peptides in regularly producing potent effects on
vascular tone, which often are restricted to selected regions in the
vasculature. Neuropeptides can thus be regarded also as being important
contributors to the regional regulation of the vasculature in selectively
responding to various physiological stimuli.

From the foregoing it is hypothesized that an increasing
concentration of Na+ perfusing the abdominal afferent collaterals of the
vagus nerve in humans would likewise produce current and stimulate the
release of AVP but not OT in the NTS, in a manner analogous to that
demonstrated by Hawthorn et al.(1988) in the ferret. This in turn should
lead to a corresponding lowering of OT voltage-gating current, a reduction
in membrane permeability and lessening of the excitability of efferent
vagal neurons, as was described by Raggenbass et al.(1992) in the rat-
tissue demonstration in vitro, thus leading to a reduction in
parasympathetic activity.

Hence , by combining the outcomes of these two studies, it becomes
possible to suggest how the regulation of parasympathetic outflow from the
brainstem along the efferent vagal pathway can be directly influenced by
the effects of a concentration dependent sodium carried current acting
along the abdominal afferent vagus nerve.


Hawthorn J, Andrews PL, Ang VT, Jenkins JS. (1988) Differential
release of vasopressin and oxytocin in response to abdominal vagal
stimulation or apomorphine in the ferret. Brain Research (Netherlands)
1988 (Jan 12); 438(1-2):193-8

Nordmann JJ, Steunkel EL. (1991) Ca++ independent regulation of
neurosecretion by intracelluar Na+.
FEBS Letters; 292: 1,2: 37-41

Raggenbasss M, Dreifuss J J. (1992) Mechanism of action of oxytocin
in ratvagal neurons:
induction of a sustained sodium-dependent current. J.Physiology (London,
England), 457: Nov. 1992, 131-42

Morris JL. (1995) Peptides as neurotransmitters in vascular autonomic
Clinical Experimental Pharmacology and Physiology 1995 (Nov);22:.792-802

Competing interests:
None declared

Competing interests: No competing interests

16 March 2006
Edward J. O'Hagan
Retired elementary school principal