Figure 5.

Spine subtype analyses of CA1 pyramidal neurons cells from Tat– or Tat+ mice. Mice previously treated with vehicle control or morphine (25 mg) time-release implants in which morphine was withheld (0 nm, “withheld”) during electrophysiological recordings. Spine subtypes (mushroom, stubby, or thin/filopodial) were analyzed individually. Dendritic spines of an indefinite or intermediate morphology were analyzed separately, thereby reducing the overall estimates of spine density compared with measurements in which all spines are counted (Fig. 3). Tat exposure reduced intermediate, stubby dendritic spine subtypes in the SO and SR of pyramidal cells in which morphine was withheld. Within the SR, withholding morphine increased the proportion of indefinite spines with concurrent Tat exposure. In the SL-M, morphine treatment increased the density of stubby spines when morphine was withheld, regardless of Tat exposure. Tat exposure reduced mushroom type spines in the SR regardless of treatment. Withholding morphine reduced SR thin/filopodial spine densities regardless of genotype. By contrast, withholding morphine interacted to significantly alter SL-M thin/filopodial spine density in Tat-exposed pyramidal cells, while withholding morphine specifically increased the proportion of thin/filopodial spines in Tat− mice; * indicates a significant difference between Tat− and Tat+ tissues; ^† indicates significant a difference between vehicle-treated and morphine-withheld tissues, p < 0.05.