Electrophysiological Studies on Merkel Cells Isolated from Rat Vibrissal Mechanoreceptors

Tactile sensation, an important mechanism animals use to explore their environment, is conveyed by various mechanoreceptors in skin (Iggo and Andres, 1982). One of the earliest to evolve in vertebrates and one with a ubiquitous distribution in the integument is a complex comprising a specialized epidermal cell, the Merkel cell, and the terminal(s) of a large myelinated sensory nerve (Halata, 1975; Diamond, 1979). Though the cell was first recognized over 100 years ago by F. Merkel (1875), its role in mechanosensory function is still in dispute in part because the relative inaccessibility of the complex in situ has prevented direct physiological recording. Recent evidence based on recordings well away from the transduction site has favoured the sensory nerve ending rather than the Merkel cell as the me chano transducer in both the mammal and lower vertebrate (Gottschaldt and Vahle-Hinz, 1981; Mills et al., 1985; Diamond et al., 1986). These findings raise questions about the actual physiological role of the Merkel cell in mechanoreception especially in view of the occurrence of synaptic features between the nerve ending and the Merkel cell (e.g., Diamond et al., 1986). To address this issue and to test further the possibility of mechanosensitivity in Merkel cells we have initiated studies aimed at understanding the physiological properties of the cell using patch clamp recording techniques (Hamill et al., 1981).