2,235 research outputs found
Activity-dependent increase of the AHP amplitude in T sensory neurons of the leech
No full textWe identified a new form of activity-dependent
modulation of the afterhyperpolarization (AHP) in tactile (T)
sensory neurons of the leech Hirudo medicinalis. Repetitive intracellular
stimulation with 30 trains of depolarizing impulses at 15-s
inter-stimulus interval (ISI) led to an increase of the AHP amplitude
(60% of the control). The enhancement of AHP lasted for 15 min.
The AHP increase was also elicited when a T neuron was activated by
repetitive stimulation of its receptive field. The ISI was a critical
parameter for the induction and maintenance of AHP enhancement.
ISI duration had to fit within a time window with the upper limit of
20 s to make the training effective to induce an enhancement of the
AHP amplitude. After recovery from potentiation, AHP amplitude
could be enhanced once again by delivering another training session.
The increase of AHP amplitude persisted in high Mg2 saline, suggesting
an intrinsic cellular mechanism for its induction. Previous
investigations reported that AHP of leech T neurons was mainly due
to the activity of the Na/K ATPase and to a Ca2-dependent K
current (IK/Ca). In addition, it has been demonstrated that serotonin
(5HT) reduces AHP amplitude through the inhibition of the Na/K
ATPase. By blocking the IK/Ca with pharmacological agents, such as
cadmium and apamin, we still observed an increase of the AHP
amplitude after repetitive stimulation, whereas 5HT application completely
inhibited the AHP increment. These data indicate that the
Na/K ATPase is involved in the induction and maintenance of the
AHP increase after repetitive stimulation. Moreover, the AHP increase
was affected by the level of serotonin in the CNS. Finally, the
increase of the AHP amplitude produced a lasting depression of the
synaptic connection between two T neurons, suggesting that this
activity-dependent phenomenon might be involved in short-term plasticity
associated with learning processes
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
Cytoprotective effect of acetyl-L-carnitine evidenced by analysis of gene expression in the rat brain
No full textAcetyl-L-carnitine (ALC), the acetyl ester of L-carnitine, is a naturally occurring substance that when administered at supraphysiological concentrations is neuroprotective. ALC plays an essential role in intermediary and mitochondrial metabolism. It has also neurotrophic and antioxidant actions. ALC has demonstrated efficacy and high tolerability in the treatment of neuropathies of various etiologies, and it is a molecule of considerable interest for its clinical application in various neural disorders, such as Alzheimer's disease and painful neuropathies, although little is known regarding the effects of ALC on gene expression. Suppression subtractive hybridization methodology was used for the generation of subtracted complementary DNA libraries and the subsequent identification of differentially expressed transcripts in the rat brain after a chronic ALC treatment. In the present paper, we provide evidences for the up-regulation of the expression of prostaglandin D(2) synthase, brain-specific Na(+)-dependent inorganic phosphate transporter, and cytochrome b oxidase, bc1 complex induced in the rat brain by ALC. On the contrary, ALC treatment down-regulates the expression of the gene of ferritin-H. Altogether, these results suggest that ALC might play a cytoprotective role against various brain stressors
LIGHT TRANSPORT IN A FLEXIBLE LIQUID SCINTILLATOR FIBER
No full textFirst results on attenuation length, photon yield and timing properties of a liquid scintillator flexible fiber are presented. Possible applications and systematic effects are also discussed
Molecular mechanisms of short-term habituation in the leech Hirudo medicinalis
No full textAlthough habituation is ubiquitous in the animal kingdom, its underlying mechanisms remain poorly understood. In this study, we began to explore the molecular cascades underlying short-term habituation in the leech Hirudo medicinalis. In H. medicinalis, a training paradigm, consisting of low-frequency
repetitive electrical stimulation of the skin, produces a gradual increase in the latency to swim that spontaneously recovers within 20–30 min. As first step in determining the molecular pathways in short-term habituation, we examined the role of Ca2+. Both Ca2+ influx through voltage-gated channels and Ca2+ release from intracellular stores were found to contribute to short-term habituation. The analysis of the downstream targets of elevated cytosolic Ca2+ revealed that the activation of the phosholipase A2 was required for the induction of short-term habituation. Finally, we reported that the recruitment of arachidonic acid metabolites, generated by the 5-lipoxygenase pathway, was also necessary for the induction of
swim induction habituation. These results provide the framework for a comprehensive characterization of the molecular underpinnings of habituation. This outcome will allow us to compare the mechanisms of habituation with those underlying other forms of nonassociative learning in the leech, such as sensitization and dishabituation, and, more in general, with those governing habituation in different vertebrate and invertebrate model systems
Effects of Catechin on cerebral arteriole vasomotion in spontaneously hypertensive rats
No full textStudies in humans have found consumption of certain flavanoid-containing foods to be associated with improvement in endothelial function and with reduction in blood pressure. In particular, catechin, a natural phenol contained in cocoa and green tea, appears to play a crucial role in the prevention of cardiovascular diseases reducing the systemic arterial blood pressure. The aim of the present study was to in vivo investigate the effects of oral administration of catechin on pial arteriolar rhythmic diameter changes in SHR in comparison with normotensive rats. Catechin was orally administered to SHR for 2 months at the dosage of 30 mg/kg b.w. The pial microcirculation was visualized by fluorescence microscopy. The vessel diameter and rhythmic variations in diameter were evaluated with computer-assisted method. Moreover, the pial arterioles were classified by Strahler scheme in five orders. On 30 min of recordings was performed the Spectral analysis in order to evaluate different frequency components: the first two in the ranges 0.005-0.0095 Hz and 0.0095-0.021 Hz (endothelial activity), the second in the range 0.021-0.052 Hz (neurogenic activity), the third in the range 0.052-0.145 Hz (myogenic activity), finally, the fourth and the fifth in the ranges 0.145-0.6 Hz (respiratory activity) and 0.6-3.0 Hz (heart beat), respectively. The data indicate that SHR treated with catechin presented an increase in the amplitude frequency components related to endothelial activity that in untreated SHR were markedly reduced. In conclusion, the catechin treatment induces the recovery of endothelial activity in SHR where this frequency component was seriously compromised compared to normotensive rats
Caulerpenyne, a toxin from the seaweed Caulerpa taxifolia, depresses afterhyperpolarization in invertebrate neuron
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