Evidence against transmitter function of met-enkephalin and chemosynaptic impulse generation in "Merkel cell" mechanoreceptors.

Using the mechanoreceptors in the cat's sinus hair follicles as a model system the recent hypothesis (Hartschuh and Weihe 1980) was tested that Merkel cells are mechanoreceptive sensory cells releasing met-enkephalin as a neurotransmitter to initiate action potentials in the terminals of type I afferent fibres. Since the met-enkephalin antagonist naloxone, even in high doses, did not affect responses in any type I mechanosensitive afferent it is unlikely that a synaptic mechanism with the release of met-enkephalin underlies impulse generation in Merkel cell-axon complexes, nor did naloxone influence the responses from other types of mechanoreceptors.