Purpose. We previously reported that histamine H3 receptors in the contralateral superior colliculus (SC) of the rats were highly up-regulated after unilateral enucleation (ARVO, 1994). In this study, quinolinic acid (QA) lesioning was used to clarify the localization of up-regulated H3 receptors in the SC. The changes of cNOS in SC after unilateral enucleation were examined using NADPH-diaphorase (NADPH-d) activity and immunohistochemistry with cNOS antibodies. The changes of histaminergic nerve fibers and glial cells after unilateral enucleation were also evaluated with histidine decarboxylase (HDC) and GFAP immunohistochemistry. Methods. Quinolinic acid injection into the unilaterally enucleated rats SC PVG rats were unilaterally enucleated (left eye). Fifteen days after the enucleation, 2 μl QA was injected into the right SC. Histamine H3 receptors in brain sections were labeled in vitro with [3H](R)-α-methylhistamine, respectively. Immunohistochemistry PVG rats were unilaterally enucleated as the same procedure and allowed to survive for 15 days. Tissue sections were reacted for NADPH-d by a procedure modified from that of Scherer-Singler et al (J Neurosci Meth, 1983) and stained immunohistochemistrically for cNOS, HDC and GFAP according to the peroxidase-antiperoxidase (PAP) method. Results. QA injection into the contralateral SC reduced the up-regulation of H3 receptors. The differences of cNOS, NADPH-d and HDC-immunoreactivity between right and left SC were not observed after unilateral enucleation. But GFAP immunoreactivity was increased in the denervated side. Conclusions. The up-regulated H3 receptors in the SC after unilateral enucleation were suggested to localize at post-synaptic sites of denervated neurons. It is known that cNOS is induced in neurons with axonal injury. cNOS immunoreactivity and NADPH-d activity in SC were not affected by unilateral enucleation. In contrast to cNOS, H3 receptors in SC were highly up-regulated at post-synaptic sites of denervated neurons. Our study suggests histaminergic neuron system is involved in denervation supersensitivity following neuronal degeneration through histamine H3 receptors.
|Journal||Investigative Ophthalmology and Visual Science|
|Publication status||Published - 1996 Feb 15|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience