42 research outputs found
The exploration of a new environment leads to the modulation of gene expression for prolonged times in the rat
No full textIn the present study we performed a transcriptional analysis in order to evaluate changes in gene expression induced by exploration in prolonged times. The analysis was carried out 3, 10 and 20 days after exploration. We analyzed the modulation of the expression levels of Pfn2, Casp3, Pdrg1, Pea15, Ywhaz genes which previously were found not modulated 2 days after exploration. Our data show that the expression of Pfn2, Casp3, Pdrg1, Pea15, Ywhaz genes was modulated at 10 or 20 days. The transcript, whose expression had been evaluated with the qRT-PCR, code for proteins which belong to the following functional categories: synaptic modulation, apoptosis, signal transduction. It is interesting to note that the modulation of the expression of these genes was evident some days after environmental exploration, and not previously at 2 days after conditioning as occurred after contextual fear conditioning (CFC). Hence it is possible to hypothesize that the spatial memory processes require a longer period of elaboration than the emotional ones, fundamental for the survival of the species
Contextual fear conditioning modulates the gene expression over time
No full textContextual fear conditioning (CFC) is a quick cognitive test based on the association context-aversive stimulus in which a single training leads to a long-term memory. Previously, we analyzed the gene expression in CFC rats, naïve rats, explor rats which had freely explored the experimental apparatus and shock only (SO) rats to which the same number of aversive shocks used in the CFC paradigm had been administered in the same CFC apparatus in less time to prevent the association between painful stimuli and apparatus. The analysis showed that 2 days after conditioning some genes (Napa, Pnf2, Casp3, Pdrg1, Ywhaz, Stmn1, Bpgm) were more expressed in CFC rats with respect to naive, explor and SO rats. Other genes (Actr3, Pea15,Tiprl) were more expressed in SO rats or in explor rats (Cplx1, Trim32, Ran), and the expression of the Tomm20 gene was greater in both CFC and explor rats in comparison with SO and naïve rats.
Herein, we have tested the expression of these genes for longer periods, at 3, 10 and 20 days after conditioning. The expression of the transcripts was assessed by qRT-PCR.
Interestingly, in CFC rats, at 3 days, the genes Tiprl and Trim32, whose expression had not been modulated at 2 days resulted more expressed with respect to naïve, explor and SO rats, whereas the gene Tomm20 was less expressed as in the SO and explor rats with respect to naïve rats. At 10 days, Trim32 gene was still more expressed in CFC rats whereas the genes Tiprl and Tomm20 returned to the constitutive level, and the gene Ran was significantly more expressed in CFC rats than in naïve, SO and explor rats. Surprisingly at 20 days, the genes Stmn1 and Tiprl again resulted significantly more expressed in CFC rats compared with naïve, SO and explor rats.
Our results outline a complex modulation of gene expression in a prolonged time point of CFC post-acquisition consolidation period
Pituitary adenylate cyclase-activating polipeptide hormone (PACAP) at very low dosages improves memory in the rat
No full text
Age-related naturally occurring depression of hippocampal neurogenesis does not affect trace fear conditioning
No full textNew neuron production throughout adulthood in granule cell layer (GCL) of rat hippocampus is a well-known phenomenon. A role of new neurons in hippocampal learning has been proposed, but the question is still open. A reduction of neural precursor proliferation in GCL of 2-month-old rats to about 20%, induced by the cytostatic agent methylazoxymethanol, was found to cause impairment in trace conditioning, suggesting a role of immature neurons in this kind of hippocampus-dependent learning (Shors et al., Hippocampus 2002;12:578-584). Neurogenesis decreases with increasing age. In this study, neural precursor proliferation and newborn cell survival were evaluated in GCL of adult rats within a range of ages following development and preceding old age. In 5-month-old rats, neural precursor proliferation was reduced to 57% and newborn cell survival was reduced to 40% in comparison to rats of 2 months of age; in 12-month-old rats, the decrease was to 5 and 4%, respectively. Consistently, the density of immature neurons decreased to 41 and 13% in 5- and 12-month-old rats, respectively. The role of neurogenesis in trace fear conditioning was studied in this natural model of neurogenesis depression. No impairment in trace fear conditioning was found both in 5- and 12-month-old rats in comparison to 2-month-old rats, notwithstanding the decrease of neurogenesis that is marked in 12-month-old rats. This finding shows that a lower rate of neurogenesis is sufficient for learning in 12-month-old rats in comparison to young rats
Contextual fear conditioning induced differentially expressed genes in the rat mid-temporal brain
No full textIn the contextual fear conditioning (CFC), a form of associative learning, the animals learn to score a new environment because of its temporal association with an aversive unconditioned stimulus (US), usually a foot shock. This learning process requires functional integrity and activation of several sub-cortical and cortical sites within the mid-temporal brain, such as hippocampus, amygdala and perirhinal cortex. Studies performed in our laboratory on the Rattus norvegicus have show that the freezing response was still exhibited one month after acquisition of CFC and that a clear correlation was found between the increase of hippocampal excitability, up to the 7-day delay, and freezing response consolidation. Long-term memory for CFC requires the synthesis of new proteins, likely as a result of the induction of genes. In order to verify this hypothesis, two different libraries of cDNA have been generated with the Suppression Subtractive Hybridisation (SSH) method. The former (forward library) contained transcripts positively conditioning-induced while the latter (reverse library) contained the negatively conditioning-modulated transcripts. The SSH method allows to isolate even the more rare transcripted genes, otherwise impossible to obtain with the other available techniques used to analyse the patterns of genic expression. Two groups of animals were employed: (i) rats subjected to a CFC paradigm training entailing the administration of aversive electrical foot shocks (8 min exposure) (conditioned group) and (ii) naïve rats never placed in the apparatus (control group). After evaluating subtraction efficiency, cDNA was directly cloned and subjected to screening. The total amount of obtained clones is 600 for the forward library and 1200 for the reverse library. In this abstract data concerning the screening of about 100 clones are reported. The analysis of the remaining clones is still in progress. Sequences of differential clones, obtained by automatic sequencer, have been analysed by comparison with sequences present in GenBank and EMBL, using program such as FASTA and BLASTN. Analysis of most interesting cDNA of the forward library have showed identity with the coding sequences for the “Complexin 1”, the “Phosphoprotein enriched in astrocytes”, the “Mithocondrial ATPase Subunit 6”, the “Tripartite motif protein 32”, the “Proteasome maturation protein” and the “Type-Iα regulatory subunit of cAMP dependent protein kinase”. In order to let evident the really differentially expressed genes a relative RT-PCR, with total RNA from control and conditioned brain, has been carried out
Contextual fear conditioning induced differentially expressed genes in the rat mid-temporal brain
No full textMaternal dietary loads of alpha-tocopherol depress protein kinase (PKC) signaling and synaptic plasticity in rat postnatal developing hippocampus and promote permanent deficits in adult offspring
No full textVitamin E (α-tocopherol) supplementation has been tested as prophylaxis against gestational disorders associated with oxidative damage. However, recent evidence showing that high maternal α-tocopherol intake can adversely affect offspring development raises concerns on the safety of vitamin E extradosages during pregnancy. Besides acting as an antioxidant, α-tocopherol depresses cell proliferation and modulates cell signaling through inhibiting protein kinase C (PKC), a kinase that is deeply involved in neural maturation and plasticity. Possible effects of α-tocopherol loads in the maturing brain, where PKC dysregulation is associated to developmental dysfunctions, are poorly known. Here, supranutritional doses of α-tocopherol were fed to pregnant and lactating dams to evaluate the effects on PKC signaling and morphofunctional maturation in offspring hippocampus. Results showed that maternal supplementation potentiates hippocampal α-tocopherol incorporation in offspring and leads to marked decrease of PKC phosphorylation throughout postnatal maturation, accompanied by reduced phosphorylation of growth-associated protein-43 and myristoylated alanine-rich C kinase substrate, two PKC substrates involved in neural development and plasticity. Although processes of neuronal maturation, synapse formation and targeting appeared unaffected, offspring of supplemented mothers displayed a marked reduction of long-term synaptic plasticity in juvenile hippocampus. Interestingly, this impairment persisted in adulthood, when a deficit in hippocampus-dependent, long-lasting spatial memory was also revealed. In conclusion, maternal supplementation with elevated doses of α-tocopherol can influence cell signaling and synaptic plasticity in developing hippocampus and promotes permanent adverse effects in adult offspring. The present results emphasize the need to evaluate the safety of supranutritional maternal intake of α-tocopherol in humans
