Molecular Characterization of Growth Hormone-producing Tumors in the GC Rat Model of Acromegaly

D.A.C. was supported by the Nicolás Monardes program of the Andalusian Ministry of Health (C-0015-2014) and by a grant from the Andalusian Ministry of Science and Innovation (CTS-7478). A.S-M and A.L.C were supported by grants from the ISCIII-Subdirección General de Evaluación y Fomento de la Investigación co-funded with Fondos FEDER (PI12/0143 and PI13/02043, respectively) and the Andalusian Regional Government (CTS-444) and a grant from Pfizer Spain. R.L.C. was supported by a grant from Andalusian Ministry of Health (PI0302-2012). R.M.L. was supported by grants from Proyecto de Investigación en Salud (FIS) PI13- 00651 (funded by Instituto de Salud Carlos III), CTS-1406, PI-0639-2012, BIO-0139 (funded by Junta de Andalucía) and by Ayuda Merck Serono 2013. J. P. C. was funded by a grant (BFU2013-43282-R) from Ministerio de Economía y Competitividad. CIBER is an initiative of Instituto de Salud Carlos III, Ministerio de Sanidad, Servicios Sociales e Igualdad, Spain. J.F.M.R. is supported by the “Sara Borrell” program from the Instituto de Salud Carlos III. R.M. Luque and J.P. Castaño have received grants and lecture fees from Ipsen and Novartis. E. Venegas-Moreno and A. Soto-Moreno received grants and lecture fees from Ipsen, Novartis and Pfizer. A. Leal-Cerro received grants from Novartis and Pfizer. David Cano received a grant from Novartis

Effects of transcranial Direct Current Stimulation (tDCS) on cortical activity: A computational modeling study.

International audienceAlthough it is well-admitted that transcranial Direct Current Stimulation (tDCS) allows for interacting with brain endogenous rhythms, the exact mechanisms by which externally-applied fields modulate the activity of neurons remain elusive. In this study a novel computational model (a neural mass model including subpopulations of pyramidal cells and inhibitory interneurons mediating synaptic currents with either slow or fast kinetics) of the cerebral cortex was elaborated to investigate the local effects of tDCS on neuronal populations based on an in-vivo experimental study. Model parameters were adjusted to reproduce evoked potentials (EPs) recorded from the somatosensory cortex of the rabbit in response to air-puffs applied on the whiskers. EPs were simulated under control condition (no tDCS) as well as under anodal and cathodal tDCS fields. Results first revealed that a feed-forward inhibition mechanism must be included in the model for accurate simulation of actual EPs (peaks and latencies). Interestingly, results revealed that externally-applied fields are also likely to affect interneurons. Indeed, when interneurons get polarized then the characteristics of simulated EPs become closer to those of real EPs. In particular, under anodal tDCS condition, more realistic EPs could be obtained when pyramidal cells were depolarized and, simultaneously, slow (resp. fast) interneurons became de- (resp. hyper-) polarized. Geometrical characteristics of interneurons might provide some explanations for this effect

Role of Reuniens Nucleus Projections to the Medial Prefrontal Cortex and to the Hippocampal Pyramidal CA1 Area in Associative Learning

We studied the interactions between short- and long-term plastic changes taking place during the acquisition of a classical eyeblink conditioning and following high-frequency stimulation (HFS) of the reuniens nucleus in behaving mice. Synaptic changes in strength were studied at the reuniens-medial prefrontal cortex (mPFC) and the reuniens-CA1 synapses. Input/output curves and a paired-pulse study enabled determining the functional capabilities of the two synapses and the optimal intensities to be applied at the reuniens nucleus during classical eyeblink conditioning and for HFS applied to the reuniens nucleus. Animals were conditioned using a trace paradigm, with a tone as conditioned stimulus (CS) and an electric shock to the trigeminal nerve as unconditioned stimulus (US). A single pulse was presented to the reuniens nucleus to evoke field EPSPs (fEPSPs) in mPFC and CA1 areas during the CS-US interval. No significant changes in synaptic strength were observed at the reuniens-mPFC and reuniens-CA1 synapses during the acquisition of eyelid conditioned responses (CRs). Two successive HFS sessions carried out during the first two conditioning days decreased the percentage of CRs, without evoking any long-term potentiation (LTP) at the recording sites. HFS of the reuniens nucleus also prevented the proper acquisition of an object discrimination task. A subsequent study revealed that HFS of the reuniens nucleus evoked a significant decrease of paired-pulse facilitation. In conclusion, reuniens nucleus projections to prefrontal and hippocampal circuits seem to participate in the acquisition of associative learning through a mechanism that does not required the development of LTP

Supplementary Material for: Neurodevelopmental Effects of Undernutrition and Placental Underperfusion in Fetal Growth Restriction Rabbit Models

<p><b><i>Introduction:</i></b> Chronic reduction of oxygen and nutrient delivery to the fetus has been related to neurodevelopmental problems. Placental underperfusion induces a significant reduction in oxygen and nutrient delivery, whereas maternal undernutrition causes mainly nutrient deficiency. A comparison of the neurodevelopmental effects of both situations in pregnant rabbits was performed. <b><i>Materials and Methods:</i></b> The placental underperfusion model was induced after uteroplacental vessel ligation at 25 days of pregnancy. The undernutrition model was induced after a reduction of 70% of the basal maternal intake at 22 days of pregnancy. Neurobehavioral tests were applied in the derived offspring at the neonatal period and over the long term. Structural brain differences were evaluated by brain networks obtained from diffusion magnetic resonance imaging. <b><i>Results:</i></b> Birth weight was significantly lower in both cases. However, stillbirth was only increased in the placental underperfusion model. Cases from both models presented poorer neurobehavioral performance and network infrastructure, being more pronounced in the placental underperfusion model. <b><i>Discussion:</i></b> Prenatal insults during the last third of gestation resulted in functional and structural disturbances. The degree of neurodevelopmental impairment and its association with structural brain reorganization seemed to be related to the type of the prenatal insult, showing stronger effects in the placental underperfusion model.</p

Microstimulation of the somatosensory cortex can substitute for vibrissa stimulation during Pavlovian conditioning

The primary somatosensory cortex (S1) contains a map representation of the body surface. We hypothesized that S1 stimulation can successfully substitute for (or be substituted by) direct stimulation of skin receptors. We prepared rabbits for evoking eyelid conditioned responses (CRs) using a trace “shock-air puff” paradigm. In a first series of experiments, animals received a conditioned stimulus (CS, a train of electrical pulses) in the whisker pad or in the S1 areas for vibrissae or for the hind limb. In the three cases, the CS was followed 250 ms from its end by an air puff presented to the cornea as an unconditioned stimulus (US). Learning curves from the three groups presented similar values, although animals stimulated with a central CS acquired their CRs faster. In a second series of experiments, animals were divided into four groups and were presented either centrally or peripherally with the same CS for six conditioning sessions. Then, the CS was switched from central to peripheral, or vice versa, for 5 additional days. Conditioned animals were not able to discriminate between peripheral (vibrissae) stimuli and stimuli presented to the corresponding S1 (vibrissae) area, but they were able to discriminate between CSs presented to S1 (hind limb) and body (vibrissae) regions. The kinetic properties of evoked CRs were not modified by CS switching. It is proposed that S1 allows the construction of somatosensory percepts of the body surface but does not allow distinguishing the central or peripheral location of the evoking stimuli

Electrical stimulation of the rostral medial prefrontal cortex in rabbits inhibits the expression of conditioned eyelid responses but not their acquisition

We have studied the role of rostral medial prefrontal cortex (mPFC) on reflexively evoked blinks and on classically conditioned eyelid responses in alert-behaving rabbits. The rostral mPFC was identified by its afferent projections from the medial half of the thalamic mediodorsal nuclear complex. Classical conditioning consisted of a delay paradigm using a 370-ms tone as the conditioned stimulus (CS) and a 100-ms air puff directed at the left cornea as the unconditioned stimulus (US). The CS coterminated with the US. Electrical train stimulation of the contralateral rostral mPFC produced a significant inhibition of air-puff-evoked blinks. The same train stimulation of the rostral mPFC presented during the CS–US interval for 10 successive conditioning sessions significantly reduced the generation of conditioned responses (CRs) as compared with values reached by control animals. Interestingly, the percentage of CRs almost reached control values when train stimulation of the rostral mPFC was removed from the fifth conditioning session on. The electrical stimulation of the rostral mPFC in well conditioned animals produced a significant decrease in the percentage of CRs. Moreover, the stimulation of the rostral mPFC was also able to modify the kinematics (latency, amplitude, and velocity) of evoked CRs. These results suggest that the rostral mPFC is a potent inhibitor of reflexively evoked and classically conditioned eyeblinks but that activation prevents only the expression of CRs, not their latent acquisition. Functional and behavioral implications of this inhibitory role of the rostral mPFC are discussed