Co-existence of tyrosine hydroxylase and calcitonin gene-related peptide in cochlear spiral modiolar artery of guinea pigs

The distribution of tyrosine hydroxylase (TH) and calcitonin gene-related p eptide (CGRP) on the cochlear spiral modiolar artery (SMA) was investigated in the guinea pig. The SMA was dissected from the modiolus so that the ent ire length of the vessel and many of its branches could be observed. Immuno histochemical labeling and double immunofluorescence were employed to local ize each compound and to determine whether the TH and CGRP co-exist in neur ons of the SMA. Microscopic examination of whole vessel preparations reveal ed numerous TH- and CGRP-positive neural networks innervating the SMA and i ts branches. The labeled neurons showed distinct arborization, varicosities and overlap, and were of different diameters. Confocal immunoflorescence m icroscopy of double-labeled TH and CGRP neurons showed that a number of the TH- and CGRP-positive neurons were colabeled. Thus, TH and CGRP partially co-exist within the neuronal innervation of SMA. These findings support;I h ypothesis that specific neuropeptide and adrenergic neurons regulate cochle ar blood now. (C) 2001 Elsevier Science B.V. All rights reserved.