Objective To further investigate the mechanism of nasal secretion closely related to the innervation patts in nasal mucosa with emphasis on the acetylcholinesterase (AChE)-positive fibers and peptidergic terminals in nasal mucosa as well as trigeminal ganglion (TG) cells.Methods Histochemical demonstration of AChE-positive fibers, immunohistochemical study of the distribution patts of multiple peptidergic terminals, double labelling of AChE and substance P (SP) and somatostatin (SOM) mRNA in situ hybridization were carried out in nasal mucosa and trigeminal ganglion (TG) in rats. Results AChE-positive terminals were mainly distributed in the mid to posterior one third of septal nasal mucosa, with greater staining density on the walls of small vessels and glands. There were fewer such terminals in turbinate mucosa. Tachykinins-ergic terminals, including substance P(SP)-, neurokinin A (NKA)-, neurokinin B(NKB)- and calcitonin gene-related peptide (CGRP)-ergic terminals, had an extensive localizations in nasal mucosa, involving the following areas: between epithelial cells, submucosa, the walls of small vessels, glands and venous sinusoids in both septal and turbinate nasal mucosa. Septal mucosa had the greater density. There were overlaps in the distribution of these peptidergic terminals. There were also vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)- and galanin (GAL)-ergic terminals in nasal mucosa. But no neurotensin (NT)- and somatostatin (SOM)-ergic terminals were found. In situ hybridization revealed SOMmRNA expression in TG cells. AChE and nine neuropeptides existed in the cytoplasms of TG cells. Besides, AChE and SP could exist simultaneously in cytoplasms of TG cells.Conclusions AChE-positive (corresponding to parasympathetic nerves) and peptidergic terminals have different distribution patts in the nasal mucosa of rats, although an overlap does exist, indicative of their different physiological effects on the regulation of nasal secretion and other functions; AChE and multiple neuropeptides in the cytoplasm of TG cells might play a role in modulating the nasal secretion in response to stimuli in the nasal mucosa.