Lack of Qu9inine-evoked Activity in Rat Trigeminal Subncleus Caudalis

摘要

Conflicting reports exist regarding the ability of quinine to activate neurons in the trigeminal system. We used the complementary approaches of single-unit electrophysiology and c-fos immunohistochemistry to investigate whether quinine (100 mM) activates chemonociceptive cells in the braninstem trigeminal subnucleus caudalis (Vc). In electrophysiological experiments, 38 units responded to noxious mechaniucal, thermal and chemical (200 mM pentanoic acid) stimuli applied to the tongue with an increase in firing rate; none responded to lingual quinine whether the quinine was presented before or after application of pentanoic acid. In the c-fos immunohistochemical experiment, both quinine and water elicited equivalent levels of fos-like immunoreactivity (FLI) in dorsomedial Vc that were significantly lower than the level of ELI evoked by pentanoic acid. These data collectively indicate that quinine does not elicity in chemonociceptive Vc neurons.