CHLOROQUINE SPECIFICALLY IMPAIRS MERKEL CELL MECHANORECEPTOR FUNCTIONIN ISOLATED RAT SINUS HAIRS

The function of Merkel cells in mechanotransduction has remained contr oversial. Single unit recordings were made from Merkel cell receptors (sinus hair type I, St I) and another slowly adapting mechanoreceptor (sinus hair type II, St II) in isolated rat sinus hairs by applying co ntrolled mechanical displacements to the hair shaft. Chloroquine (50-3 00 mu M) caused a concentration dependent inhibition of Merkel cell re ceptor responses to mechanical stimulation. In contrast, both stimulat ed and spontaneous spike activity of St II receptors was increased by the same concentrations of chloroquine. Ultrastructural examination of chloroquine treated sinus hairs revealed swollen Merkel cells with mu ltiple vacuoles and randomly distributed granules while other neural a nd surrounding structures showed no striking morphological changes. Th ese results suggest that the Merkel cell plays a mechanotransducer rol e in Merkel cell receptors.