Consolidation of associative memories appears to require extracellular signal-related kinase2 (ERK2) activation, which is modulated by several factors, including neurotransmitter receptor stimulation. Here we show that in vitro stimulation of either H2 or H3 histaminergic receptors activates ERK2 in hippocampal CA3 pyramidal cells. In behaving animals, bilateral posttraining injections into the dorsal hippocampus of histamine H2 or H3 receptor agonists improve memory consolidation after contextual fear conditioning. Local administration of U0126, a selective inhibitor of ERK kinase, prevents memory improvements exerted by the agonists, without causing any behavioral effect per se. This is the first evidence of a positive correlation between ERK phosphorylation and memory improvement. Moreover, we demonstrate that the brain histaminergic system regulates hippocampal ERK cascade. Finally, our data indicate that early ERK2 hippocampal activation is not required for the expression of long-term fear memories.

No abstract

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages could compensate for reduced adult survival, corresponding to “compensatory recruitment”. To date, evidence of compensatory recruitment in response to habitat modification is restricted to plants, limiting understanding of its importance as a response to global change. We used the yellow-bellied toad ( Bombina variegata ), an amphibian occupying a broad range of natural and anthropogenic habitats, as a model species to test for and to quantify compensatory recruitment. Using an exceptional capture–recapture dataset composed of 21,714 individuals from 67 populations across Europe, we showed that adult survival was lower, lifespan was shorter, and actuarial senescence was higher in anthropogenic habitats, especially those affected by intense human activities. Increased recruitment in anthropogenic habitats fully offset reductions in adult survival, with the consequence that population growth rate in both habitat types was similar. Our findings indicate that compensatory recruitment allows toad populations to remain viable in human-dominated habitats and might facilitate the persistence of other animal populations in such environments.

Secretory activity of serous (poison) cutaneous glands was studied with light and transmission electron microscopy over the ontogenetic cycle of the Black-legged Dart Frog Phyllobates bicolor.Serous gland activity includes two steps: biosynthesis and maturation. Biosynthesis is performed by the rough endoplasmic reticulum, smooth endoplasmic reticulum, and Golgi apparatus, and follows the usual pathways of exocrine secretory processes. Maturation is typical of anuran serous glands, which accumulate their products in syncytial secretory units. Maturation involves merging processes between secretory deposits (vesicles and/or granules) distally from the Golgi stacks, as well as an increase in the surface area between the syncytial cytoplasm and the secretory vesicles/granules. In P. bicolor, this interface area increases through the formation of peculiar cytoplasmic outgrowths. These outgrowths allow transport processes involved in maturational changes of secretory product. During maturational storage, the secretory products of P. bicolor acquire a repeating substructure of spherical to short tubular subunits. This recurrent pattern is seen in cutaneous poisons of several anuran species, regardless of their phylogenetic relationships. Among anurans, condensing serous cutaneous products into repeating aggregations of subunits appears to be a successful strategy, which allows intracytoplasmic accumulation of pharmacologically active and/or toxic molecules through various post-Golgian processes. The present findings provide evidence of a novel repertory of cytological activities that stress the large diversity of the maturational pathways leading to the peculiar repeating arrangement of secretory subunits.

It is well documented that N-methyl-3,4-methylenedioxyamphetamine (MDMA, ecstasy) releases brain serotonin (5-HT; 5-hydroxytryptamine), noradrenaline (NE; norepinephrine), and dopamine, but the consequent effect on brain functioning remains elusive. In this study, we characterized the effects of MDMA on electrically evoked responses in the ventral CA1 region of a rat hippocampal slice preparation. Superfusion with MDMA (10 mM, 30 min) increased the population spike amplitude (PSA) by 48.9731.2% and decreased population spike latency (PSL) by 1037139 ms (both: mean7SD, n ¼ 123; po0.0001, Wilcoxon test), without affecting field excitatory postsynaptic potential (fEPSP). This effect persisted for at least 1 h after MDMA washout; we have called this EPSP-spike potentiation (ESP) by MDMA, ESP MDMA . Antagonism of GABAergic transmission did not prevent ESP MDMA , suggesting that an increase in excitability of pyramidal cells underlies this MDMA action. Block of serotonin transporter (SERT) with citalopram or 5-HT depletion with (7)