Trigeminal nasal-specific neurons respond to nerve growth factor with substance-P biosynthesis.

ABSTRACT

BACKGROUND: Nerve growth factor (NGF) has been found to induce substance-P biosynthesis in large-diameter A-fibres vagal airway neurons. However, the effect of NGF on trigeminal neurons innervating the nasal mucosa of the mouse has not been investigated so far. OBJECTIVE: NGF has been implicated in allergic diseases by modulating sensory nerves. Therefore, the present study investigated the effect of NGF on neuropeptides expression such as substance-P and glutamate in nasal trigeminal neurons. METHODS: Using neuronal tracing in combination with double labelling immunohistochemistry the expression of substance-P, glutamate and neurofilament protein 68-kDa expression was examined in nasal-specific trigeminal neurons of BALB/c-mice. RESULTS: The numbers of Fast blue-labelled trigeminal neurons expressing substance-P were significantly increased after NGF exposure (NGF-treated ganglia 16.4 +/- 0.6% vs. control 7.0 +/- 0.4%, PNGF treatment-induced substance-P biosynthesis in neurofilament-positive (NGF-treated ganglia 8.6 +/- 0.2% vs. control 1.1 +/- 0.2%, Pneurofilament-negative (NGF-treated ganglia 7.8 +/- 0.6% vs. control 5.9 +/- 0.4%, P=0.05) and non-glutamatergic neurons (NGF-treated ganglia 11.8 +/- 1.9% vs. control 1.1 +/- 1.0%, PNGF exposure.

CONCLUSION:

Under normal conditions, substance-P was expressed in nasal-specific neurofilament-negative, glutamatergic and C-fibre neurons. Nasal-specific trigeminal neurons respond to NGF treatment with substance-P biosynthesis in non-glutamatergic, neurofilament-positive as well as -negative neurons. These findings suggest that nasal-specific trigeminal neurons are composed of heterogenous subpopulations in relation to their peptide profiles and therefore may have different functions in neurogenic airway inflammation.