Abstract
Background: Our previous study have investigated that nicotine reinnervates perivascular sympathetic adrenergic nerves lesioned by topically applied phenol in the rat mesenteric artery in vivo, and markedly increased levels of nerve growth factor (NGF) contents and the expression of NGF receptor TrkA in superior cervical ganglia (SCG), which were inhibited by the pretreatment of nicotinic acetylcholine receptor (nAChR) antagonist hexamethonium (Takatori S et al., Eur J Pharmacol, 748: 1-9, 2015.). Furthermore, we demonstrated that nicotine increases neurite outgrowth of SCG via activation of 7 nAChR in vitro. The aim of this study is to examine inhibitory effects of nicotine on neurite outgrowth of primary cultured-SCG cells and PC12 cells in vitro.
Methods: SCG cells isolated from Wistar neonate rats and PC12 cells were primarily cultured for 5 days. Numbers of neurite outgrowth from cell body were measured in the presence of nicotine (0.001-100 mM). Hexamethonium (100 µM) or -bungarotoxin (100 µM) was co-incubated with each concentration of nicotine (0.1-10 mM) for 5 days.
Results: Nicotine (0.01-0.3 mM) significantly increased numbers of neurite outgrowth from tyrosine hydroxylase-immunopositive SCG cells, while nicotine-induced neurite increase was gradually reduced by high concentration of 0.1-10 mM. The facilitatory or inhibitory effect of nicotine (0.1 or 10 mM) on neurite outgrowth in SGC cells was markedly inhibited or augmented by the treatment of -bungarotoxin and hexamethonium, respectively. In PC12 cells, nicotine at low concentrations (0.01-1 mM) caused a concentration-dependent increase in numbers and length of neurite outgrowth. However, higher concentrations (10-100 mM) of nicotine decreased numbers and length of neurite outgrowth compared to control in a concentration-dependent manner.
Conclusion: These results suggest that nicotine has facilitatory and inhibitory action on neurite outgrowth (This study was supported by Smoking Research Foundation).
