Biocytin Filling of Adult Gonadotropin-Releasing Hormone Neuronsin SituReveals Extensive, Spiny, Dendritic Processes

Publisher Website
Google Scholar
Abstract
Ultrastructural studies suggest that GnRH neurons receive relatively few synaptic inputs. However, these techniques are biased toward the analysis of portions of the neuron contain- ing GnRH peptide. Using acute brain slices prepared from transgenic GnRH-green fluorescent protein mice, individual fluorescing GnRH neurons were identified, patched, and filled with the small-molecular-weight dye biocytin. Cells were subsequently visualized with an avidin-conjugated flu- orophore, and their morphological characteristics were ana- lyzed by confocal microscopy. In total, 45 GnRH neurons from seven adult male and eight diestrus female mice were exam- ined. Unexpectedly, we found that GnRH neurons possess re- markably long dendritic processes, in some cases extending over 1000 m distal to the cell body. The somata and dendrites of all GnRH neurons were decorated with an assortment of spine-like protrusions, including filopodia, in an heteroge- neous manner. Overall, GnRH neurons had a mean dendritic spine density of 0.4 spines/m, with the highest densities found in the first 50 m of the dendrite. GnRH neurons with dendrites running in a horizontal orientation had signifi- cantly (P < 0.05) more spines than dendrites with a vertical orientation. The comparison of male and female GnRH neu- rons revealed no sexually differentiated characteristics of so- mal or dendritic spine density. Using a technique in which the full extent of the GnRH neuron can be visualized, we demon- stratehereapreviouslyunrecognizedGnRHneuronmorphol- ogy of long dendrites covered in spines. These observations suggest that GnRH neurons are not poorly innervated and that they receive abundant excitatory synaptic inputs. (En- docrinology 146: 1163-1169, 2005)

This publication has 0 references indexed in Scilit: