Electrical pharyngeal stimulation increases substance P level in saliva

Background: Substance P (SP) is a neuropeptide known to enhance the swallow response. It likely acts as a neurotransmitter in the pharyngeal mucosa in response to local stimuli. It has been proposed that dysphagia after stroke may be related to reduced levels of SP, which therefore constitutes a therapeutic target. In the present pilot study, we evaluated whether electrical pharyngeal stimulation (EPS), a neuromodulation device to enhance cortical reorganization for the restoration of swallowing function after brain injury, is able to increase SP in saliva or serum.

Methods: In a randomized crossover study design, 20 healthy volunteers were treated with 10 min of real (0.2-ms pulses, 5 Hz, 280 V, stimulation intensity (mA) individually adjusted to tolerance level) or sham EPS on two separate sessions. Stimulation was delivered via a pair of bipolar ring electrodes mounted on an intraluminal catheter positioned in the pharynx. Blood and saliva samples were taken prior to, during, and up to 1 h after EPS and analyzed for their SP concentration by ELISA.

Key results: Following real EPS but not sham stimulation, SP levels in saliva increased immediately and significantly about 28% (p < 0.01) compared to baseline. Serum levels remained unchanged.

Conclusions & inferences: Electrical pharyngeal stimulation is able to induce pharyngeal SP release in healthy subjects.