THE SYMPATHETIC AND PARASYMPATHETIC NATURE OF NEUROPEPTIDE Y-IMMUNOREACTIVE NERVE-FIBERS IN THE MAJOR SALIVARY-GLANDS OF THE RAT

The distribution and origin of neuropeptide Y in the major salivary gl ands of the rat was studied by indirect immunofluorescence technique. Numerous nerve fibres immunoreactive for the peptide were seen in the parotid and sublingual glands. Most of the fibres were located around blood vessels and salivary acini. In the submandibular gland the numbe r of immunoreactive nerve fibres around the acini was lower in compari son with that in the parotid and sublingual glands. Some immunoreactiv e nerve fibres were also found around or along intra- and interlobular ducts in all major salivary glands. A large number of the neuropeptid e-containing neuronal cell bodies and nerve fibres were detected in th e sympathetic superior cervical ganglion. Sympathetic postganglionic n erve trunks of this ganglion contained numerous immunoreactive nerve f ibres as well. A subpopulation of the neuronal cell bodies in the subm andibular ganglion were immunoreactive to neuropeptide Y. Both uni- an d bilateral superior cervical ganglionectomies caused a significant de crease in the number of immunoreactive nerve fibres around the blood v essels in all the major salivary glands. However, these denervations d id not affect the density of nerve fibres around the acini and ducts. On the contrary, unilateral parasympathetic denervation by sectioning the auriculotemporal nerve reduced the fibres around the secretory aci ni in the parotid gland remarkably, while only a minor reduction in th e density of immunoreactive fibres associated with the blood vessels o f the gland was detected. Unilateral electrocoagulation of the trigemi nal nerve branches caused no detectable change in the density of immun oreactive nerve fibres in any of the major salivary glands. On the bas is of the present findings it is concluded that neuropeptide Y-reactiv e nerve fibres present in all major salivary glands around the blood v essels seem to be mainly sympathetic, whereas those around the acini a nd ducts seems to be of parasympathetic origin.