Functional magnetic resonance imaging (fMRI) changes and saliva production associated with acupuncture at LI-2 acupuncture point: a randomized controlled study

Abstract

Background: Clinical studies suggest that acupuncture can stimulate saliva production and reduce xerostomia (dry mouth). We were interested in exploring the neuronal substrates involved in such responses.

Methods: In a randomized, sham acupuncture controlled, subject blinded trial, twenty healthy volunteers received true and sham acupuncture in random order. Cortical regions that were activated or deactivated during the interventions were evaluated by functional magnetic resonance imaging (fMRI). Saliva production was also measured.

Results: Unilateral manual acupuncture stimulation at LI-2, a point commonly used in clinical practice to treat xerostomia, was associated with bilateral activation of the insula and adjacent operculum. Sham acupuncture at an adjacent site induced neither activation nor deactivation. True acupuncture induced more saliva production than sham acupuncture.

Conclusion: Acupuncture at LI-2 was associated with neuronal activations absent during sham acupuncture stimulation. Neuroimaging signal changes appear correlated to saliva production.

Figures

Figure 1

Experimental Design. Each subjects received both true and sham acupuncture in a randomized order. Boxcar design of fMRI paradigm was used. Each fMRI paradigm lasted a total of 8 minutes and 40 seconds. Stimulation (true or sham acupuncture) was initiated at the time points indicated with the downward arrows and stopped at those indicated with the upward arrows (panel 1a). During true acupuncture, a real acupuncture needle was inserted at the LI-2 acupuncture point. During sham acupuncture, a Streitberger placebo needle was applied at a non-acupuncture (sham) point (panel 1b).

Figure 2

fMRI changes associated with true acupuncture at LI-2. Sagittal, coronal and axial view (respectively) of cortical areas activated by the true acupuncture paradigm.

Figure 3

Specific activation by true acupuncture versus placebo acupuncture. Activation regions shown by fMRI signals associated with true acupuncture were compared to those from sham acupuncture. Panel 3a: sagittal, coronal and axial view (respectively) of activation in the insula and adjacent operculi. Panel 3b: Correlation of saliva production with ROI volumes.

Figure 4

Schematic representation of the gustation-salivation neuronal circuitry and how acupuncture may interact with it. Green lines represent input neural signals, red lines output signals. Solid lines represent physiological response of salivation to gustatory stimuli. Dashed lines represent physiological signals from other cortices. Dotted lines represent the hypothetical pathway through which acupuncture activates the opercular and insular cortices. Areas A: thalamus; B: the insular and opercular cortices; C: salivatory nuclei in the pons.