Fig. 4.

MORs are important for the morphine modulation of dendritic spines. (A–C) Images were processed with deconvolution. (A) A cortical neuron that was cultured from control mice before and after application of morphine is shown. Top two arrows indicate two dendritic spines that gradually retracted and became thin tiny protrusions. Bottom two arrows indicate two dendritic spines that disappeared in 3 days. (B) A neuron that was cultured from MOR knockout mice before and after morphine treatment is shown. (C) A rat neuron before and after the double treatment of CTOP and morphine is shown. Arrows in B and C denote an increase in the density of dendritic spines. (D) The number of dendritic spines per 100 μm of dendrites in morphine-treated control mouse neurons (open bars) and μ receptor knockout mouse neurons (filled bars). (E) The density of spines in three groups of drug-treated rat neurons. (F) An untreated control and a morphine-treated EGFP-labeled neuron were stained alive with Cy3 (red)-conjugated antibody against the N terminus of GluR1 subunits. Arrows denote protrusions that contain N-GluR1; triangles denote protrusions that contain no detectable GluR1. (G) The proportion of dendritic protrusions (Left) and spines (Right) that contain AMPA receptors in morphine-treated neurons (+M) and untreated neurons (–M).