VIP innervation of the tongue in vertebrates

An immunohistochemical study was carried out in order to investigate the occurrence of vasoactive intestinal polypeptide (VIP) in intralingual nervous tissue of different species. The study revealed that VIP-immunoreactive (IR) nerves and ganglia were widely found in all species studied. The following areas of the tongue tissue contain VIP-IR nerves: (1) Within the perivascular plexus many VIP-IR nerves can be found adjoining AV-anastomoses and medium-sized arteries, whereas the veins exhibit only a moderate number. (2) Intralingual ganglia contain VIP-IR perikarya and varicosities. (3) Lingual glands are regularly innervated by VIP-IR periglandular plexus. (4) Sub- and intraepithelial nerves react to VIP immunohistochemically and occur in different locations. The results of this study indicate that VIP is an important neuropeptide of the intralingual nerves. It is suggested that VIP has various functions as a neurotransmitter and/or neuromodulator which may be summarized as follows: (1) the vascular and glandular innervation can be assumed to be of an efferent nature, and (2) some subepithelial and intraepithelial nerves are afferent fibers.