Reflex swallowing elicited by water and chemical substances applied in the oral cavity, pharynx, and larynx of the rabbit.

Water and various chemical solutions were applied to the oral cavity, pharynx, and larynx of anesthetized rabbits to study their effects on the swallowing reflex. Laryngeal stimulation: Water was an effective stimulus in eliciting reflex swallowing; NaCL depressed this reflex. The effect of salt solutions on swallowing was dependent on anion species. Weakly hydrated anions had a depressing effect while greatly hydrated anions had a facilitating effect. The order of the depressing effect of the anions was Br-greater than SCN- greater than CL- congruent to NO3 -, and the order of the facilitating effect of anions was citrate greater than SO42 - greater than HCO3-. Oral and pharyngeal stimulation: Water elicited swallowing; however, this effect was less marked than that in the larynx. NaCL in concentrations lower than 200 mM had a depressing effect while at higher concentration it had a facilitating effect. Sucrose, acetic acid, and alcohol evoked successive swallowing in the first two or three trials. It was found that water applied to the laryngeal region had the marked effect of eliciting reflex swallowing and that most gustatory substances infused into the oral and pharyngeal regions had a facilitating effect on the initation of swallowing.