Localization of preproenkephalin mRNA-expressing cells in rat auditory brainstem with in situ hybridization.

Hair cells and auditory nerve dendrites in the inner ear are innervated by pontine neurons that have been demonstrated by immunochemical techniques to contain several neurotransmitters, including acetylcholine and the opioid peptide enkephalins and dynorphins. The functions of these nerve fibers are not known, but may involve modifying auditory sensitivity to low intensity stimuli. In the guinea pig the opioid pathways originate in the lateral superior olivary region.

The fluorescent indicator pyranine is suitable for measuring stromal and cameral pH in vivo.

Three pH-sensitive fluorescent indicators (fluorescein, bis-carboxyethyl-carboxyfluorescein and pyranine) were studied to determine their usefulness as probes for the living cornea and anterior chamber. Of the three dyes, pyranine had properties which render it almost ideally suited for this purpose. Adequate concentrations are reached in the cornea and anterior chamber after topical administration; measurements can be made by fluorophotometry for many hours.