NITRIC-OXIDE SYNTHASE IMMUNOREACTIVE NERVES IN RAT AND FERRET SALIVARY-GLANDS, AND EFFECTS OF DENERVATION

Nitric oxide has been implicated in mechanisms mediating nerve-evoked vasodilatory and secretory responses in salivary glands. In the presen t study, the occurrence and distribution of nitric oxide synthase (NOS )-immunoreactive nerves in ferret and rat salivary glands were investi gated using immunocytochemistry with rabbit and sheep NOS antisera, an d using NADPH-diaphorase enzyme histochemistry. In the parotid, subman dibular and sublingual glands of the rat and the ferret, NOS-immunorea ctive varicose terminals encircled acini and arteries of various sizes . In the ferret, collecting ducts were also supplied with NOS-immunore active fibres. In the rat, only the granular ducts of the submandibula r gland were supplied with such fibres. The NOS-immunoreactive innerva tion of acinar cells was more abundant in the rat than in the ferret, whereas the opposite was true for the innervation of blood vessels. No NOS immunoreactivity was observed in the vascular endothelium. In bot h species, NOS-positive ganglionic cell bodies were found in the hilar regions of the submandibular and sublingual glands, whereas none coul d be detected in the parotid glands. NADPH-diaphorase reactivity had t he same neuronal distribution as NOS immunoreactivity and, in addition , NADPH-diaphorase reactivity was expressed in ductal epithelium. Neit her sympathetic denervation (by removal of the superior cervical gangl ion) nor treatment with the sensory neurotoxin capsaicin reduced the N OS-immunoreactive innervation of the parotid gland. However, parasympa thetic denervation (by cutting the auriculo-temporal nerve) caused an almost total disappearance of the NOS-immunoreactive innervation. The present findings provide a morphological background to the suggested r ole of nitric oxide in parasympathetic secretory and vascular response s of salivary glands.