Endogenous nerve growth factor stimulation: effects on auditory pathway neural cells in a mouse model.

OBJECTIVE: In the present study, we investigated whether high-pressure hypotonic saline solution (Hphss) affects the basal level of Nerve Growth Factor (NGF) and expression of receptors in the cochlea, bark earing, retina, and visual cortex. MATERIALS AND METHODS: For this study, we used three weeks old female Sprague Dawley (SD) rats (n = 12). Rats were housed in polypropylene cages and were kept under standard conditions (12 h light:12 h dark cycle) with free access to water and food (Purina chow food). A specific dispenser was employed to deliver sterile hypotonic saline at high pressure (pressing emission level (PEL): 7 g/s; emission time (ET): 0.5 s). Rats were divided into two groups: untreated (n = 6) and treated with Hphss (n = 6), three times per day, for 10 consecutive days. Treatment was performed in both nostrils with 50 µl of Hphss using a microsyringe equipped with a plastic tip. RESULTS: We observed a significant enhancement in the level of NGF in the cochlea and bark earing, but not in the retina and visual cortex. This is likely because the nasolacrimal duct pathway does not appear to have an effect on the retina, and the visual cortex appears to be too far from the cribriform plate to be reached by nasal NGF. CONCLUSIONS: This treatment can significantly protect and/or delay degeneration of cochlear auditory NGF-target cells. It is free from side effects and can be used in chronic diseases for as long as needed. It remains to be investigated whether the effects of short-term therapy are long-lasting, or if the treatment must be repeated.

High-pressure physiological saline isotonic solution administration enhances brain NGF and NGF-receptors expression.

OBJECTIVE: Nerve growth factor (NGF) is a neurotrophin which promotes and regulates the survival of neurons in the peripheral nervous system. The aim of this study was to investigate the effect of high-pressure administration of sterile physiological saline isotonic solution (HpPSIS) into nasal cavity of laboratory animals on NGF levels and NGF-receptor expression in the olfactory bulbs and brain. MATERIALS AND METHODS: For this study we used three weeks old female Sprague Dawley SD rats (n=48). Rats were divided into two groups, the first one treated delivering physiological saline solution with a normal syringe modified at the extremity to fit the rats' nostril (5 ml) (n=24) and the second one treated spray with HpPSIS (n=24 rats). Rats were treated three times a day either for 5 consecutive days (shorth term treatment) or 10 consecutive days (longer treatment) in both nostrils of HpPSIS delivered at high pressure (pression emission level: PEL: 7 g/sec for emission time ET: 0.5 sec) with a specific forced spray erogator. Untreated rats received a similar manipulation three times a day through a syringe in the nostrils, but no HpPSIS administration. RESULTS: The results of these studies highlight the possibility that endogenous enhancement of NGF by stimulation of NGF-producing cells within the nasal cavities and also in the CNS represent a novel experimental approach to enhance the brain NGF levels with a new therapy. HpPSIS treatment further enhances the presence of NGF in the four brains examined. Indeed, a significant increase of NGF was first observed after 5 days of HpPSIS treatment, compared to HpPSIS untreated rats. The increase was over 25% in the OB, ST, HI and in CX, while 10 days after HpPSIS treatments the levels of NGF were even higher. These differences were statistically significant, p < 0.05. CONCLUSIONS: It was found that forced administration of HpPSIS enhances the presence of these neurotrophic signals, not only in the olfactory bulbs, but also in forebrain cholinergic neurons, which are known to degenerate as result of memory loss and brain aging, including Alzheimer Disease. These findings for the first time in the literature demonstrate the possibility of enhancing the endogenous NGF to protect NGF-damaged neurons. Since the enhanced expression of NGF was first observed after 5 days of treatment and higher after 10 days of treatment, a reasonable hypothesis is that longer HpPSIS treatment might further enhance the level of NGF in brain and olfactory bulbs.