Article

Adult-Born Hippocampal Neurons Are More Numerous, Faster Maturing, and More Involved in Behavior in Rats than in Mice

Unit on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 11/2009; 29(46):14484-95. DOI: 10.1523/JNEUROSCI.1768-09.2009
Source: PubMed

ABSTRACT

Neurons are born throughout adulthood in the hippocampus and show enhanced plasticity compared with mature neurons. However, there are conflicting reports on whether or not young neurons contribute to performance in behavioral tasks, and there is no clear relationship between the timing of maturation of young neurons and the duration of neurogenesis reduction in studies showing behavioral deficits. We asked whether these discrepancies could reflect differences in the properties of young neurons in mice and rats. We report that young neurons in adult rats show a mature neuronal marker profile and activity-induced immediate early gene expression 1-2 weeks earlier than those in mice. They are also twice as likely to escape cell death, and are 10 times more likely to be recruited into learning circuits. This comparison holds true in two different strains of mice, both of which show high rates of neurogenesis relative to other background strains. Differences in adult neurogenesis are not limited to the hippocampus, as the density of new neocortical neurons was 5 times greater in rats than in mice. Finally, in a test of function, we find that the contribution of young neurons to fear memory is much greater in rats than in mice. These results reveal substantial differences in new neuron plasticity and function between these two commonly studied rodent species.

Download full-text

Full-text

Available from: Jason Snyder, Jul 22, 2014
  • Source
    • "En résumé, le blocage de la neurogenèse adulte hippocampique, que ce soit par méthode chimique, physique ou génétique, induit un certain nombre de déficits de mémoires dépendantes de l'hippocampe . Les quelques résultats contradictoires observés peuventêtrepeuventêtre en partie expliqués par les types de mémoiresmémoiresétudiées, l'hétérogénéité des protocoles utilisés , les différentes espèces, mais aussi les différentes méthodesdeBruel-Jungerman et al., 2006 ;Snyder et al., 2009)Snyder et al., 2009). De même, la réexposition réexpositionà un environnement enrichi familier ainsi que le rap- peì a long terme d'une mémoire spatiale ou encore le réapprentissage 4 semaines après lapremì ere exposition recrutent des nouveaux neuronesâgésneuronesˆneuronesâgés de 1 ` a 2 semaines (Tashiro et al., 2007 ;Trouche et al., 2009 ;Epp et al., 2011b). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A defining characteristic of the brain is its remarkable capacity to undergo activity-dependent functional and structural remodelling via mechanisms of plasticity that form the basis of our capacity to encode and retain memories. The prevailing model of how our brain stores new information about relationships between events or new abstract constructs suggests it resides in activity-driven modifications of synaptic strength and remodelling of neural networks brought about by cellular and molecular changes within the neurons activated during learning. To date, the idea that a form of activity-dependent synaptic plasticity known as long-term potentiation, or LTP, and the associated synaptic growth play a central role in the laying down of memories has received considerable support. Beyond this mechanism of plasticity at the synapse, adult neurogenesis, i.e. the birth and growth of new neurons, is another form of neural plasticity that occurs continuously in defined brain regions such as the dentate gyrus of the hippocampus. Here, based on work in the hippocampus, we review the processes and mechanisms of the generation and selection of new neurons in the adult brain and the accumulating evidence that supports the idea that this form of neural plasticity is essential to store and lead to retrievable hippocampal-dependent memories.
    Full-text · Article · Jan 2016 · Biologie Aujourd'hui
  • Source
    • "While the enhanced cocaine-induced CPP in the p21 -/-mice could be due to increased salience of the drug reward, the performance differences observed with U50,488-induced CPA under the same protocol support the hypothesis that p21 -/-mice have increased learning capacity, which may be mediated by increased neurogenesis. Multiple studies suggest a correlation between adult neurogenesis and learning capability (Shors et al., 2001;Shors et al., 2002;Raber et al., 2004;Winocur et al., 2006;Wojtowicz et al., 2008;Snyder et al., 2009a;Snyder et al., 2009b;Deng et al., 2010;Cameron and Glover, 2015), such as that necessary for successful conditioned place preference and aversion. Data presented here support the finding byPechnick "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study investigated the functional role of cyclin-dependent kinase inhibitor 1a (Cdkn1a or p21) in cocaine-induced response using a knockout mouse model. Acute locomotor activity following cocaine administration (15 mg/kg, i.p.) was decreased in p21(-/-) mice, whereas cocaine-induced place preference was enhanced. Interestingly, κ-opioid-induced place aversion was also significantly enhanced. Concentration-dependent analysis of locomotor activity in response to cocaine demonstrated a rightward shift in the p21(-/-) mice. Additionally, pretreatment with a serotonin antagonist did not alter cocaine-induced CPP in this model, consistent with the involvement of dopaminergic signaling. Cocaine exposure increased p21 expression exclusively in the ventral sector of the hippocampus of rodents following either contingent or non-contingent drug administration. Increased p21 expression was accompanied by increased histone acetylation of the p21 promoter region in rats. Finally, increased neurogenesis in the dorsal hippocampus of p21(-/-) mice was also observed. These results show that functional loss of p21 altered the acute locomotor response to cocaine and the conditioned responses to either rewarding or aversive stimuli. Collectively, these findings demonstrate a previously unreported involvement of p21 in modulating responses to cocaine and in motivated behaviors.
    Full-text · Article · Jan 2016 · Journal of Pharmacology and Experimental Therapeutics
  • Source
    • "The second population of DGCs is more active, with signals frequent enough to be recorded in vivo, and does not rapidly orthogonalize. This second population of broadly tuned DGCs is proposed to represent hyperactive, immature adult-born dentate granule cells (abDGCs), and it may be missed by IEG studies (Huckleberry et al., 2015; Jessberger & Kempermann, 2003; Snyder, Glover, Sanzone, Kamhi, & Cameron, 2009; Snyder, Choe, et al., 2009). [An alternative explanation may be that, like CA1 and CA3, the DG uses alternate encoding methods to represent different types of information (Leutgeb, Leutgeb, Barnes, et al., 2005); however, these discrepancies may also be due to differences in behavioral protocols (Leutgeb, Leutgeb, Treves, et al., 2005; Wills et al., 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hippocampal adult neurogenesis is thought to subserve pattern separation, the process by which similar patterns of neuronal inputs are transformed into distinct neuronal representations, permitting the discrimination of highly similar stimuli in hippocampus-dependent tasks. However, the mechanism by which immature adult-born dentate granule neurons cells (abDGCs) perform this function remains unknown. Two theories of abDGC function, one by which abDGCs modulate and sparsify activity in the dentate gyrus and one by which abDGCs act as autonomous coding units, are generally suggested to be mutually exclusive. This review suggests that these two mechanisms work in tandem to dynamically regulate memory resolution while avoiding memory interference and maintaining memory robustness.
    Full-text · Article · Nov 2015 · Neurobiology of Learning and Memory
Show more