The Journal of Neuroscience, July 1, 2000, 20(13):5163-5169
Calcitonin Gene-Related Peptide Suppresses Hair Cell Responses to
Mechanical Stimulation in the Xenopus Lateral Line
Organ
Gerald P.
Bailey1, 3 and
William F.
Sewell1, 2
1 Eaton-Peabody Laboratory, Department of
Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston,
Massachusetts 02114, 2 Program in Neuroscience and
Department of Otology and Laryngology, Harvard Medical School, Boston,
Massachusetts 02115, and 3 Department of Pathology, Boston
University School of Medicine, Boston, Massachusetts 02118
The presence of calcitonin gene-related peptide (CGRP) in the
efferent fibers of virtually every hair cell organ studied suggests it
may serve some fundamental but heretofore unknown role in control of
hair cell function. We examined the effects of CGRP on spontaneous and
stimulus-evoked discharge patterns in an in vitro
preparation of the lateral line organ of Xenopus laevis.
Discharge patterns were determined by sinusoidally displacing the
cupula with a glass micropipette driven with a piezoelectric device
while recording afferent fiber activity. All afferent fibers had
characteristic frequencies of 16-32 Hz. Responses synchronized to
cupular displacements as small as 20 nm. CGRP suppressed responses of
the lateral line organ to displacement while increasing spontaneous
discharge rate. In the presence of CGRP, stimulus-response curves were
shifted 10 dB toward higher displacement levels. The suppression of
stimulus-evoked responses suggests a function for CGRP as an efferent
neurotransmitter that is similar to that of cholinergic efferent
transmission in other hair cell organs. The 10 dB shift toward larger
displacements makes it comparable in magnitude with the effects of
electrical stimulation of efferents in the mammalian cochlea. This
suggests a significant role for CGRP in efferent modulation of the
output of this mechanosensory organ.
Key words:
sensory; cochlea; neurotransmitter; efferent; vestibular; calcitonin gene-related peptide; acetylcholine
Copyright © 2000 Society for Neuroscience 0270-6474/00/20135163-07$05.00/0
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