Distinct patterns of DeltaFosB induction in brain by drugs of abuse

Abstract

The transcription factor DeltaFosB accumulates and persists in brain in response to chronic stimulation. This accumulation after chronic exposure to drugs of abuse has been demonstrated previously by Western blot most dramatically in striatal regions, including dorsal striatum (caudate/putamen) and nucleus accumbens. In the present study, we used immunohistochemistry to define with greater anatomical precision the induction of DeltaFosB throughout the rodent brain after chronic drug treatment. We also extended previous research involving cocaine, morphine, and nicotine to two additional drugs of abuse, ethanol and Delta(9)-tetrahydrocannabinol (Delta(9)-THC, the active ingredient in marijuana). We show here that chronic, but not acute, administration of each of four drugs of abuse, cocaine, morphine, ethanol, and Delta(9)-THC, robustly induces DeltaFosB in nucleus accumbens, although different patterns in the core vs. shell subregions of this nucleus were apparent for the different drugs. The drugs also differed in their degree of DeltaFosB induction in dorsal striatum. In addition, all four drugs induced DeltaFosB in prefrontal cortex, with the greatest effects observed with cocaine and ethanol, and all of the drugs induced DeltaFosB to a small extent in amygdala. Furthermore, all drugs induced DeltaFosB in the hippocampus, and, with the exception of ethanol, most of this induction was seen in the dentate. Lower levels of DeltaFosB induction were seen in other brain areas in response to a particular drug treatment. These findings provide further evidence that induction of DeltaFosB in nucleus accumbens is a common action of virtually all drugs of abuse and that, beyond nucleus accumbens, each drug induces DeltaFosB in a region-specific manner in brain.

(c) 2008 Wiley-Liss, Inc.

Figures

Fig. 1

Double-labeling fluorescence immunohistochemistry using the anti-FosB (pan-FosB, Santa-Cruz) or anti-FosB (C-terminus) antibody through the nucleus accumbens of animals treated with acute or chronic cocaine and a control rat. The pan-FosB antibody stains both ΔFosB and FosB-positive nuclei (note nuclei from acute cocaine treatment stain with this antibody in green, and double stain with both antibodies “merge” row), whereas the C-terminus antibody stains FosB-positive nuclei only (note the absence of labeling in chronic cocaine tissue labeled with this antibody). All nuclei in the chronic cocaine-treated tissue are ΔFosB positive as they are stained only with the pan-FosB antibody and not with the C-terminal antibody. The inset shows a nucleus accumbens section from a fosB knockout mouse stained with the pan-FosB antibody; the lack of staining demonstrates the specificity of the antibody for fosB gene products. The background on this panel is intensified to demonstrate that no staining (brighter red) was observed. Scale bar = 50 µm.

Fig. 2

Induction of ΔFosB in the rat nucleus accumbens in a control rat (A) or after chronic treatment with ethanol (B), morphine (C), or cocaine (D). Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody. Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.

Fig. 3

Induction of ΔFosB in the rat caudate putamen in a control rat (A) or after chronic treatment with ethanol (B), morphine (C), or cocaine (D). Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody. Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.

Fig. 4

Induction of ΔFosB in mouse brain after chronic Δ9-THC treatment. Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody in control (A, C, E) and chronic Δ9-THC (B, D, F) animals. Note that chronic Δ9-THC treatment increased FosB-like immunoreactivity in the nucleus accumbens (NAc) core and shell, caudate putamen (CPu; A, B), and prefrontal cortex (PfC; E, F). Note that ΔFosB induction in striatal regions reached statistical significance for NAc core only, despite strong trends in the NAc shell and CPu as shown in the figure (see Fig. 5). Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.

Fig. 5

Quantification of ΔFosB induction in striatal regions after chronic morphine, Δ9-THC, ethanol, and cocaine treatments. The bar graphs show the mean number of ΔFosB+ cells in control animals and in animals subjected to chronic morphine, Δ9-THC, ethanol, or cocaine treatments in the core and shell subregions of the nucleus accumbens (NAc) and in the dorsal striatum (caudate-putamen, CPu). Data are expressed as mean ± SEM (n = 6–10 animals in each group). *P < 0.05 by t-test.

Fig. 6

Quantification of ΔFosB induction in striatal regions after chronic cocaine self-administration. The bar graphs show the mean number of ΔFosB+ cells in control animals and in animals subjected to the cocaine treatments, in the core and shell subregions of the nucleus accumbens (NAc) and the dorsal striatum (caudate- putamen, CPu). Data are expressed as mean ± SEM (n = 6–10 animals in each group). *P < 0.05 by t-test. Note no significant differences between self-administering animals and their yoked counterparts.

Fig. 7

Induction of ΔFosB in the prefrontal cortex in a control rat (A) or after chronic treatment with ethanol (B), morphine (C), or cocaine (D). Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody. Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.

Fig. 8

Induction of ΔFosB in the basal lateral and central medial nuclei of the amygdala of a control rat (A) or in rats given chronic ethanol (B), morphine (C), or cocaine (D) treatments. Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody. Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.

Fig. 9

Induction of ΔFosB in the hippocampus of a control rat (A) or in rats given chronic ethanol (B), morphine (C), or cocaine (D) treatments. Levels of FosB-like immunoreactivity were analyzed by immunohistochemistry using a pan-FosB antibody. Labeling with the C-terminus antibody revealed no positive cells (not shown). Scale bar = 50 µm.