Adult neurogenesis—a reality check

Adult hippocampal neurogenesis in the pathogenesis of addiction and dual diagnosis disorders

BACKGROUND

As knowledge deepens about how new neurons are born, differentiate, and wire into the adult mammalian brain, growing evidence depicts hippocampal neurogenesis as a special form of neuroplasticity that may be impaired across psychiatric disorders. This review provides an integrated-evidence based framework describing a neurogenic basis for addictions and addiction vulnerability in mental illness.

METHODS

Basic studies conducted over the last decade examining the effects of addictive drugs on adult neurogenesis and the impact of neurogenic activity on addictive behavior were compiled and integrated with relevant neurocomputational and human studies.

RESULTS

While suppression of hippocampal neurogenic proliferation appears to be a universal property of addictive drugs, the pathophysiology of addictions involves neuroadaptative processes within frontal-cortical-striatal motivation circuits that the neurogenic hippocampus regulates via direct projections. States of suppressed neurogenic activity may simultaneously underlie psychiatric and cognitive symptoms, but also confer or signify hippocampal dysfunction that heightens addiction vulnerability in mental illness as a basis for dual diagnosis disorders.

CONCLUSIONS

Research on pharmacological, behavioral and experiential strategies that enhance adaptive regulation of hippocampal neurogenesis holds potential in advancing preventative and integrative treatment strategies for addictions and dual diagnosis disorders.

Regional features of the expression of genes involved in neurogenesis and apoptosis in the brain of adult rats

The expression of mRNA of genes involved in neurogenesis and apoptosis (Apaf1, Ascl1, Bax, Bcl2, Casp3, Casp8, Casp9, Dffb, Myh10, Naip2, Napa, Notch2, Numb, Pura, S100a6, Tnf) in the prefrontal cortex, hippocampus, and cerebellum was studied in adult rats. The content of mRNA of these genes (except Apaf1) was several-fold higher in the cerebellum than in the hippocampus and brain cortex. In the hippocampus, the expression of Apaf1 was significantly lower than in the prefrontal cortex, while the expression of Ascl1, Pura, S100b, and Tnf was higher. Regional differences in the direction, strength, and numbers of significant correlations between the expression of the studied genes were detected. Documented differences in gene expression were regarded as validation of the structural and functional cooperation of neurogenesis and apoptosis at the molecular genetic level.