We stated that SART-stressed guinea pigs showing nasal mucosal
hypersensitivity would serve as an animal model for the in vivo evaluation of
antiallergic drugs. In the present study, the mode of action of
Neurotropin on nasal
allergy compared with those of
antiallergic drugs was studied by using SART-stressed guinea pigs. Daily administrations of
Neurotropin improved the
methacholine-induced hypersecretion and
histamine-evoked sneeze response, which are parameters of nasal mucosal
hypersensitivity, and increased the density of
muscarinic ACh receptors located on the nasal mucosa caused by SART stress. In addition, the inhibitory action on nasal secretion in a passively sensitized model was more intense in SART-stressed guinea pigs than in normal ones.
Ketotifen and
tranilast were also found to have marked effects on nasal secretion in the passively sensitized SART-stressed model, but only had weak effects on nasal mucosal
hypersensitivity.
Neurotropin significantly potentiated the action of
ketotifen or
tranilast. Thus, at least part of the inhibitory effect of
Neurotropin on nasal symptoms such as watery secretion and
sneezing is thought to have been brought forth through the regulatory action on nasal mucosal
hypersensitivity, and its combined use with
antiallergic drugs would be a very effective therapeutic regimen for nasal
allergy.