The induction of behavioural sensitization is associated with cocaine-induced structural plasticity in the core (but not shell) of the nucleus accumbens

Repeated exposure to cocaine increases the density of dendritic spines on medium spiny neurons in the nucleus accumbens (Acb) and pyramidal cells in the medial prefrontal cortex (mPFC). To determine if this is associated with the development of psychomotor sensitization, rats were given daily i.p. injections of 15 mg/kg of cocaine (or saline) for 8 days, either in their home cage (which failed to induce significant psychomotor sensitization) or in a distinct and relatively novel test cage (which induced robust psychomotor sensitization). Their brains were obtained 2 weeks after the last injection and processed for Golgi–Cox staining. In the Acb core (AcbC) cocaine treatment increased spine density only in the group that developed psychomotor sensitization (i.e. in the Novel but not Home group), and there was a significant positive correlation between the degree of psychomotor sensitization and spine density. In the Acb shell (AcbS) cocaine increased spine density to the same extent in both groups; i.e. independent of psychomotor sensitization. In the mPFC cocaine increased spine density in both groups, but to a significantly greater extent in the Novel group. Furthermore, when rats were treated at Home with a higher dose of cocaine (30 mg/kg), cocaine now induced psychomotor sensitization in this context, and also increased spine density in the AcbC. Thus, the context in which cocaine is experienced influences its ability to reorganize patterns of synaptic connectivity in the Acb and mPFC, and the induction of psychomotor sensitization is associated with structural plasticity in the AcbC and mPFC, but not the AcbS.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73532/1/j.1460-9568.2004.03612.x.pd

Patterns of ash (Fraxinus excelsior L.) colonization in mountain grasslands: the importance of management practices

International audienceWoody colonization of grasslands is often associated with changes in abiotic or biotic conditions or a combination of both. Widely used as fodder and litter in the past traditional agro-pastoral system, ash (Fraxinus excelsior L.) has now become a colonizing species of mountain grasslands in the French Pyrenees. Its present distribution is dependent on past human activities and it is locally controlled by propagule pressure and abiotic conditions. However, even when all favourable conditions are met, all the potentially colonizable grasslands are not invaded. We hypothesize that management practices should play a crucial role in the control of ash colonization. From empirical field surveys we have compared the botanical composition of a set of grasslands (present and former) differing in management practices and level of ash colonization. We have displayed a kind of successional gradient positively linked to both ash cover and height but not to the age of trees. We have tested the relationships between ash presence in grassland and management types i.e. cutting and/or grazing, management intensity and some grassland communities' features i.e. total and local specific richness and species heterogeneity. Mixed use (cutting and grazing) is negatively linked to ash presence in grassland whereas grazing alone positively. Mixed use and high grazing intensity are directly preventing ash seedlings establishment, when low grazing intensity is allowing ash seedlings establishment indirectly through herbaceous vegetation neglected by livestock. Our results show the existence of a limit between grasslands with and without established ashes corresponding to a threshold in the intensity of use. Under this threshold, when ash is established, the colonization process seems to become irreversible. Ash possesses the ability of compensatory growth and therefore under a high grazing intensity develops a subterranean vegetative reproduction. However the question remains at which stage of seedling development and grazing intensity these strategies could occur

Para-infectious brain injury in COVID-19 persists at follow-up despite attenuated cytokine and autoantibody responses

To understand neurological complications of COVID-19 better both acutely and for recovery, we measured markers of brain injury, inflammatory mediators, and autoantibodies in 203 hospitalised participants; 111 with acute sera (1–11 days post-admission) and 92 convalescent sera (56 with COVID-19-associated neurological diagnoses). Here we show that compared to 60 uninfected controls, tTau, GFAP, NfL, and UCH-L1 are increased with COVID-19 infection at acute timepoints and NfL and GFAP are significantly higher in participants with neurological complications. Inflammatory mediators (IL-6, IL-12p40, HGF, M-CSF, CCL2, and IL-1RA) are associated with both altered consciousness and markers of brain injury. Autoantibodies are more common in COVID-19 than controls and some (including against MYL7, UCH-L1, and GRIN3B) are more frequent with altered consciousness. Additionally, convalescent participants with neurological complications show elevated GFAP and NfL, unrelated to attenuated systemic inflammatory mediators and to autoantibody responses. Overall, neurological complications of COVID-19 are associated with evidence of neuroglial injury in both acute and late disease and these correlate with dysregulated innate and adaptive immune responses acutely