Ultrastructure of enkephalin- and substance P-immunoreactive axon terminals in the hypoglossal nucleus of the chicken.
The morphology and distribution of leucine-enkephalin (LENK)- and substance P (SP)-containing axon terminals in the hypoglossal nucleus of the chicken was investigated immunocytochemically at the electron microscopic level. The major findings of the present study were as follows: 1) Both LENK- and SP-immunoreactive (IR) profiles including unmyelinated axons, varicosities and axon terminals were found throughout the hypoglossal nucleus. 2) LENK-IR profiles without synapses (preterminal axons and varicosities) were observed more frequently (66%) than LENK-IR synaptic profiles (34%). In contrast, SP-IR synaptic terminals were seen more often (68%) than SP-IR terminals without synapses (32%). 3) Both LENK- and SP-IR synaptic terminals ending on dendrites were more numerous (83% and 94%, respectively) than those making synapses on somata (17% and 6%, respectively). 4) The average diameter of SP-IR synaptic terminals were significantly larger than that of LENK-IR ones. 5) Both LENK- and SP-IR synaptic terminals contained numerous small clear vesicles and several large dense-cored vesicles (LDV). Although both LENK- and SP-IR synaptic terminals contained LDV consistently, SP-IR synaptic terminals contained significantly more LDV than LENK-IR types. 6) Postsynaptic dense bodies (Taxi bodies) were seen more frequently in SP-IR synaptic terminals than in LENK-IR ones. These findings confirm both LENK and SP innervation in the hypoglossal nucleus and suggest a functional role as neuromodulator for the two neuropeptides in tongue control.
Wang
J
J
Department of Veterinary Anatomy, School of Agriculture, Nagoya University, Japan.
Watanabe
T
T
Ohmori
Y
Y
Naito
J
J
Fukuta
K
K
D000818:Animals; D001369:Axons / Q000737:chemistry* / Q000648:ultrastructure; D002645:Chickens; D004745:Enkephalins / Q000032:analysis*; D007002:Hypoglossal Nerve / Q000737:chemistry* / Q000648:ultrastructure; D008297:Male; D013373:Substance P / Q000032:analysis*
D004745:Enkephalins; D013373:Substance P