A final class of trigeminal fibers forms synaptic contacts with solitary chemoreceptor cells in the nasal cavity of mice (and perhaps other predators) (Zancanaro et al., 1999; Finger et al., 2003).
The chemoreceptor cells were sensitive to a broad-spectrum search stimulus and to either ammonium ion or taurine, in some cases at concentrations down to [10.sup.-6] mol [1.sup.-1] (Cate and Derby, 2002a).