COEXPRESSION OF NOCICEPTOR PROPERTIES IN DORSAL-ROOT GANGLION NEURONSFROM THE ADULT-RAT IN-VITRO

The cell body of sensory neurons in vitro has been used as a model to study the electrophysiological properties of afferent terminals. A lim itation of this approach has been the ability to identify the function of the neuron studied. In the present study, we have tested the hypot hesis that a putative nociceptor can be identified in vitro based on t he expression of properties associated with nociceptors in vivo. A com bination of patch-clamp electrophysiological and immunohistochemical t echniques were used to describe the expression of nociceptor propertie s in acutely cultured dorsal root ganglion neurons from the adult rat. These properties include: a small cell body diameter; the presence of the neuropeptides substance P and calcitonin-gene related peptide; a shoulder (inflection) on the falling phase of the somal action potenti al, a response to the algogenic agent capsaicin, and sensitization in response to prostaglandin E(2). Our results indicate that the frequenc y of expression of each of these properties varies in a manner consist ent with that predicted from observations made in vivo, and that when one property is present in any given neuron, the other properties are also likely to be present. These data support the suggestion that the cell body of adult rat dorsal root ganglion neurons in vitro can be us ed to study the electrophysiological properties of nociceptors.