title: Enkephalin-like immunoreactivity in the chick brainstem: possible relation to the cochlear efferent system.
abstract: Mammalian lateral olivocochlear (LOC) neurons that are immunoreactive for choline acetyltransferase (ChAT) are also immunoreactive for enkephalin (Enk). To determine whether cochlear efferent neurons in birds might also contain Enk-like immunoreactivity (Enk-LI), we studied the auditory brainstem of the domestic chicken using antisera to ChAT, leucine-enkephalin (L-Enk) and methionine-enkephalin (M-Enk). Enk-LI terminals are found around, but not within, the superior olivary nucleus (SO) and the nucleus of the lateral lemniscus, pars intermedia (LLi). A moderate concentration of Enk-LI terminals is found ventromedial to the ventral facial nucleus (VIIv) where the ventrolateral group of ChAT-I cochlear efferent neurons is located. After colchicine injections into the lateral ventricle, a population of intensely stained Enk-LI perikarya was found in the nucleus of the lateral lemniscus, pars ventralis (LLv) with scattered cells in the LLi and the nucleus subceruleus ventralis (SCv). The distribution of Enk-LI and ChAT-I somata, however, never overlapped, even in adjacent sections. Thus, in the chick, Enk-LI perikarya are not distributed in areas where cochlear efferent neurons are found. Instead, a dense concentration of Enk-I terminals can be found in areas containing ChAT-I cochlear efferent neurons. The source of these enkephalinergic terminals may be a population of Enk-LI cells in the LLv.
authors.affiliation: Department of Zoology, University of Maryland, College Park 20742-4415, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Code
authors.forename: C E
authors.initials: CE
authors.lastname: Carr
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000737:chemistry* / Q000166:cytology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002645:Chickens / Q000033:anatomy & histology*; D002795:Choline O-Acetyltransferase / Q000032:analysis; D003051:Cochlea / Q000166:cytology* / Q000187:drug effects; D003078:Colchicine / Q000008:administration & dosage / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000032:analysis; D004745:Enkephalins / Q000032:analysis*; D005154:Facial Nerve / Q000737:chemistry / Q000166:cytology; D007150:Immunohistochemistry; D009476:Neurons, Efferent / Q000737:chemistry* / Q000166:cytology; D009847:Olivary Nucleus / Q000737:chemistry / Q000187:drug effects; D014278:Trigeminal Nuclei / Q000737:chemistry / Q000166:cytology; D014630:Vagus Nerve / Q000737:chemistry / Q000166:cytology
chemical_list: D004745:Enkephalins; D004743:Enkephalin, Leucine; D002795:Choline O-Acetyltransferase; D003078:Colchicine