Early growth hormone (GH) treatment promotes relevant motor functional improvement after severe frontal cortex lesion in adult rats.

A number of studies, in animals and humans, describe the positive effects of the growth hormone (GH) treatment combined with rehabilitation on brain reparation after brain injury. We examined the effect of GH treatment and rehabilitation in adult rats with severe frontal motor cortex ablation. Thirty-five male rats were trained in the paw-reaching-for-food task and the preferred forelimb was recorded. Under anesthesia, the motor cortex contralateral to the preferred forelimb was aspirated or sham-operated. Animals were then treated with GH (0.15 mg/kg/day, s.c) or vehicle during 5 days, commencing immediately or 6 days post-lesion. Rehabilitation was applied at short- and long-term after GH treatment. Behavioral data were analized by ANOVA following Bonferroni post hoc test. After sacrifice, immunohistochemical detection of glial fibrillary acid protein (GFAP) and nestin were undertaken in the brain of all groups. Animal group treated with GH immediately after the lesion, but not any other group, showed a significant improvement of the motor impairment induced by the motor lesion, and their performances in the motor test were no different from sham-operated controls. GFAP immunolabeling and nestin immunoreactivity were observed in the perilesional area in all injured animals; nestin immunoreactivity was higher in GH-treated injured rats (mainly in animals GH-treated 6 days post-lesion). GFAP immunoreactivity was similar among injured rats. Interestingly, nestin re-expression was detected in the contralateral undamaged motor cortex only in GH-treated injured rats, being higher in animals GH-treated immediately after the lesion than in animals GH-treated 6 days post-lesion. Early GH treatment induces significant recovery of the motor impairment produced by frontal cortical ablation. GH effects include increased neurogenesis for reparation (perilesional area) and for increased brain plasticity (contralateral motor area).

Chronic administration of risperidone in a rat model of schizophrenia: a behavioural, morphological and molecular study.

In the present work we analyzed the effect of the chronic administration of risperidone (2mg/kg over 65 days) on behavioural, morphological and molecular aspects in an experimental model of schizophrenia obtained by bilateral injection of ibotenic acid into the ventral hippocampus of new-born rats. Our results show that during their adult lives the animals with hippocampal lesions exhibit different alterations, mainly at behavioural level and in the gene expression of dopamine D(2) and 5-HT(2A) receptors. However, at morphological level the study performed on the prefrontal cortex did not reveal any alterations in either the thickness or the number of cells immunoreactive for c-Fos, GFAP, CBP or PV. Overall, risperidone administration elicited a trend towards the recovery of the values previously altered by the hippocampal lesion, approaching the values seen in the animals without lesions. It may be concluded that the administration of risperidone in the schizophrenia model employed helps to improve the altered functions, with no significant negative effects.

El trasplante de astrocitos encapsulados mejoran el déficit motor en la habilidad manual producido por la lesión de la corteza frontal en ratas adultas / Transplant of encapsulated astrocyte ameliorate lesion-induced motor deficits in adults rats with frontal cortex injury

Objetivo: Investigar la capacidad de trasplantes de astrocitos encapsulados en esferas de alginato de recuperar el déficit en la habilidad manual producida por la lesión de la corteza frontal, en ratas adultas. Material y metodología: Se utilizaron ratas Wistar, y se emplearon pruebas conductuales, cultivos celulares, técnica de encapsulación de células y trasplantes. Los animales se condicionaron en un test de habilidad motora fina y se determinó su mano preferente. Se lesionó la corteza frontal contralateral a la mano preferente y se evaluó la efectividad de la lesión mediante el test de conducta. En un grupo de animales lesionados se trasplantó astrocitos encapsulados en esferas de alginato en la cavidad producida por la lesión; en un segundo grupo, se trasplantó tejido cortical fetal; y en un tercer grupo, se implantó esferas de alginato sin células. Resultados: A los tres meses post-trasplante, tanto los animales con trasplantes de astrocitos encapsulados como con trasplantes de tejido cortical mejoraron el déficit motor inducido por la lesión. Los animales con trasplantes de esferas de alginato vacías no experimentaron mejoría. Conclusión: Los trasplantes de astrocitos encapsulados mejoran, a largo plazo, el deficit motor. El alginato indujo efectos secundarios en el huésped (AU)

Objetive: To investigate whether transplants of encapsulated astrocytes in alginate spheres were able to recover the deficit in motor skills produced by frontal cortex lesion, in adult rats. Material and method: Male Wistar rats were used. Behavioral test, tissue culture, astrocyte transplants and immunocytochemical and histological techniques were applied. Animals were conditioned in a paw reaching for food task and the preferred paw determine. Lesion was produced in the frontal cortex contralateral to the preferred paw and the effectiveness of the lesion tested. In one group of lesion animals, encapsulated astrocytes in alginate spheres were implanted in the lesion cavity; in a second group, fetal cortical tissue was used as donor material; while in a third group empty alginate spheres were implanted. Results: Three months after grafting, the rats with encapsulated astrocyte or with fetal cortical tissue transplants ameliorated the lesion-induced motor deficit.The rats with implant of empty alginate spheres showed no improvement. Conclusion: Transplants of encapsulated astrocytes in alginate spheres induce a long- term improvement of motor lesion deficits. The alginate induced long-term side effects on the host (AU)

Recuperación de la habilidad motora mediante trasplantes neurales en ratas adultas con lesión de la corteza frontal / Motor skill recovery through neural transplants in adult rats with frontal cortex damage

Objetivo: Investigar los mecanismos involucrados en la recuperación funcional de alteraciones motoras producidas por la lesión de la corteza frontal mediante trasplantes neurales embrionarios, en ratas adultas. Material y metodología: Utilizamos ratas machos, de raza Wistar, empleando pruebas conductuales, métodos electrofisiológicos y técnicas inmunohistoquímicas e histológicas. Los animales se condicionaron en un test motor específico de habilidad motora fina y se determinó su mano preferente. Se realizó una lesión en la corteza frontal contralateral a la mano preferente y se evaluó la efectividad de la lesión mediante el test de conducta. En un grupo de animales lesionados se trasplantó tejido cortical embrionario en la cavidad producida por la lesión; en un segundo grupo, se utilizó tejido fetal amigdalino como tejido donante; y en un tercer grupo, se trasplantó nervio ciático de rata adulta. Los tres grupos se compararon con un grupo de animales control. Resultados: A los tres meses post-trasplante, los animales con trasplantes de tejido fetal amigdalino y con trasplantes de tejido cortical mejoraron el déficit motor producido por la lesión. Los animales con trasplantes de nervio ciático no presentaron ninguna mejoría. Conclusión: Los trasplantes de tejido amigdalino inducen una mejoría similar a la obtenida con los trasplantes de tejido cortical. El origen ontogenético, en parte común, del tejido amigdalino y el tejido cortical podría estar implicado en los mecanismos subyacentes a la recuperación funcional (AU)

Objetive: To investigate the mechanisms by which neural transplants contribute to functional recovery of the motor disorders produced by frontal cortex damage in adult rats. Material and methods: Male Wistar rats were used, with the application of behavioral tests, electrophysiological methods and immunohistochemical and histological techniques. The animals were conditioned using a specific fine motor skill test, with determination of the dominant paw. Damage was produced in the frontal cortex contralateral to the dominant paw, with evaluation of the effectiveness of the lesion based on the behavioral test. In one group of damaged animals embryonic cortical tissue was implanted in the cavity left by the lesion. In a second group fetal amygdaline tissue was used as donor material, while in a third group adult rat sciatic nerve was implanted. The three groups were compared with a control group. Results: Three months after grafting, the rats with fetal amygdaline tissue and with transplanted cortical material improved of the motor defect induced by the lesion. The rats with grafted sciatic nerve showed no improvement. Conclusion: Amygdaline tissue grafts induce improvement similar to that recorded with cortical tissue transplants. The partially shared ontogenetic origin of amygdaline and cortical tissue could be implicated in the functional recovery mechanisms (AU)

Chronic administration of risperidone to healthy rats: a behavioural and morphological study.

Taking into account that most of the experimental research into the effects of antipsychotic drugs has mainly focused on behavioural aspects, the aim of the present work is to investigate the effects of a chronic therapeutic dose of risperidone (1 mg/kg/day during 140 days) on both behavioural and morphological aspects in healthy rats. The behavioural results revealed only minor modifications in prepulse inhibition, showing the risperidone-treated group higher values at 70 days of treatment with respect to the vehicle group. Moreover, in the open-field test, this group showed a greater incidence of grooming. In the active avoidance test, no differences were found between the groups studied. Additionally, in the morphological study performed to analyse cortical thickness and the number of GFAP-, CaBP-, PV- and Fos-immunostained cells no differences were seen between the two groups studied. It is important to note that the risperidone-treated group showed a slight increase in the total number of cells counted, although this increase was not significant. Our results indicate that the chronic administration of therapeutic doses of risperidone does not produce any dramatic behavioural or morphological changes in healthy animals.

Single-cell recordings: a method for investigating the brain's activation pattern during exercise.

The precision of human movements to generate skills as accurate as the exercises performed by athletes are the consequence of a long and complex learning process. These processes involve a great amount of the nervous system's structures. Electrophysiological techniques have been largely used to highlight brain functions related to the control of these kinds of movements. These methods cover invasive and non-invasive techniques which have been applied to humans and experimental animals. We describe here electrophysiological techniques that are used in behaving animals. Especially, we will focus on the analysis and results obtained from single-cell recording in the prefrontal cortex to explain the relationship between single neuronal activity and movement during locomotion. In addition, we will show how, analyzing these results, that we can characterize the integrative role of neurons involved in the control of locomotion. The objective is to demonstrate single-cell recording techniques as suitable methods to study, in experimental animals, the brain's activation pattern during exercise.

Beta-Amyloid peptide25-35 depresses excitatory synaptic transmission in the rat basolateral amygdala "in vitro".

The effects of beta-amyloid peptide25-35 on resting membrane potential, spontaneous and evoked action potential and synaptic activity have been studied in basolateral amygdaloid complex on slices obtained from adult rats. Intracellular recordings reveal that perfusion with beta-amyloid peptide25-35 at concentrations of 400 nM and less did not generate any effect on resting membrane potential. However, concentrations in the range of 800-1200 nM produced an unpredictable effect, depolarization and/or hyperpolarization, which were blocked by tetrodotoxin or 6-cyano-7-nitroquinoxaline-2,3-dione+D-(-)-2-amino-5-phosphonopentanoic acid together with bicuculline. Excitatory and inhibitory evoked responses mediated by glutamic acid or gamma-aminobutyric acid decreased in amplitude after beta-amyloid peptide25-35 perfusion. Additionally, results obtained using the paired-pulse protocol offer support for a presynaptic mode of action. To determine which type of receptors and/or channels are involved in the presynaptic mechanism of action, a specific blocker of alpha-7 nicotinic receptors (methyllycaconitine citrate) or L-type calcium channel blockers (calcicludine or nifedipine) were used. beta-amyloid petide25-35 decreased excitatory postsynaptic potentials amplitude in control conditions and also in slices permanently perfused with methyllycaconitine citrate. However, this effect was blocked in slices perfused with calcicludine or nifedipine suggesting the involvement of the L-type calcium channels. On the whole, these experiments provide evidence that beta-amyloid peptide25-35 affects neurotransmission in basolateral amygdala and its action is mediated through L-type calcium channels.

Functional recovery of skilled forelimb use in rats obliged to use the impaired limb after grafting of the frontal cortex lesion with homotopic fetal cortex.

The long-term effect of transplanting embryonic frontal cortex into a unilateral frontal cortex lesion has been studied in adult rats. Before surgery, activity in an open field, muscular strength of both forelimbs, and performance in a paw-reaching-for-food task were scored in 26 rats. In 21 animals a unilateral cortex lesion was then made in the forelimb motor area of the hemisphere contralateral to the preferred paw in the paw-reaching-for-food task, while the other 5 animals were sham-operated. On retesting, the lesion animals changed the preferred paw. A solid homotopic transplant of embryonic tissue (embryonic day 17) was then placed in the lesion cavity in 11 of the lesion rats. Three months later neither lesion alone nor lesion plus transplantation affected open field behavior and muscular strength, but the lesion permanently affected performance in the paw-reaching-for-food task, as shown by a change of preferred paw and a functional deficit in the paw contralateral to the lesion. Transplantation ameliorated the deficits caused by the lesion, but this was only evident when animals were forced to reach with the paw contralateral to the lesion plus transplant. The behavioral results were independent of the size of the lesion and graft. Connections between graft and host tissue were studied by means of the fluorescent tracer 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI). A dense array of labeled fibers was found in the host cortex adjacent to the transplant. The results suggest that functional recovery depends on grafting but is only evident when the animal is obliged to use the affected limb.

Muscarinic activation of a non-selective cationic conductance in pyramidal neurons in rat basolateral amygdala.

In the present study, a cationic membrane conductance activated by the acetylcholine agonist carbachol was characterized in vitro in neurons of the basolateral amygdala. Extracellular perfusion of the K+ channel blockers Ba2+ and Cs+ or loading of cells with cesium acetate did not affect the carbachol-induced depolarization. Similarly, superfusion with low-Ca2+ solution plus Ba2+ and intracellular EGTA did not affect the carbachol-induced depolarization, suggesting a Ca2+-independent mechanism. On the other hand, the carbachol-induced depolarization was highly sensitive to changes in extracellular K+ or Na+. When the K+ concentration in the perfusion medium was increased from 4.7 to 10 mM, the response to carbachol increased in amplitude. In contrast, lowering the extracellular Na+ concentration from 143.2 to 29 mM abolished the response in a reversible manner. Results of coapplication of carbachol and atropine, pirenzepine or gallamine indicate that the carbachol-induced depolarization was mediated by muscarinic cholinergic receptors, but not the muscarinic receptor subtypes M1, M2 or M4, specifically. These data indicate that, in addition to the previously described reduction of a time- and voltage-independent K+ current (IKleak), a voltage- and time-dependent K+ current (IM), a slow Ca2+-activated K+ current (sIahp) and the activation of a hyperpolarization-activated inward rectifier K+ current (IQ), carbachol activated a Ca2+-independent non-selective cationic conductance that was highly sensitive to extracellular K+ and Na+ concentrations.

Cholinergic responses of morphologically and electrophysiologically characterized neurons of the basolateral complex in rat amygdala slices.

The electrophysiological properties, the response to cholinergic agonists and the morphological characteristics of neurons of the basolateral complex were investigated in rat amygdala slices. We have defined three types of cells according to the morphological characteristics and the response to depolarizing pulses. Sixty-six of the recorded cells (71%) responded with two to three action potentials, the second onwards having less amplitude and longer duration (burst). In a second group, consisting of 21 cells (22%), the response to depolarization was a train of spikes, all with the same amplitude (multiple spike). Finally, seven neurons (7%) showed a single action potential (single spike). Burst response and multiple-spike neurons respond to the cholinergic agonist carbachol (10-20 microM) with a depolarization that usually attained the level of firing. This effect was accompanied by decreased or unchanged input membrane resistance and was blocked by atropine (1.5 microM). The depolarizing response to superfusion with carbachol occurred even when synaptic transmission was blocked by tetrodotoxin, indicating a direct effect of carbachol. Similarly, the depolarization by carbachol was still present when the M-type conductance was blocked by 2 mM Ba2+. The carbachol-induced depolarization was prevented by superfusion with tetraethylammonium (5 mM). Injection of biocytin into some of the recorded cells and subsequent morphological reconstruction showed that "burst" cells have piriform or oval cell bodies with four or five main dendritic trunks; spines are sparse or absent on primary dendrites but abundant on secondary and tertiary dendrites. This cellular type corresponds to a pyramidal morphology. The "multiple-spike" neurons have oval or fusiform somata with four or five thick primary dendritic trunks that leave the soma in opposite directions; they have spiny secondary and tertiary dendrites. Finally, neurons which discharge with a "single spike" to depolarizing pulses are round with four or five densely spiny dendrites, affording these neurons a mossy appearance. The results indicate that most of the amygdaloid neurons respond to carbachol with a depolarization. This effect was concomitant with either decrease or no change in the membrane input resistance and was not blocked by the addition of Ba2+, an M-current blocker, indicating that a conductance pathway other than K+ is involved in the response to carbachol.

Electrophysiological study of prefrontal neurones of cats during a motor task.

The prefrontal cortex is involved in many processes, some of which are related to motor activity such eye movements and speech. Experimental data exist that suggest that prefrontal cortical activity occurs in relation to attention, short-term memory, affective discrimination, and complex forms of motor behaviour, i.e. anticipatory preparation, motor sequences, programming of speech, etc. We were interested in studying participation of this cortical region in locomotion. For this purpose, recordings were made of unitary activity in the prefrontal cortex of chronically prepared cats walking on an exercise belt that was moving at a speed of 0.1 m/s. From a total of 63 neurones in the prefrontal area from which recordings were made, 37 (59%) changed their activity during locomotion, 28 of which (76%) increased and 9 of which (24%) decreased their frequency of discharge; the remaining 26 units (41%) showed no locomotor-related change in activity. The results obtained show that 59% of prefrontal units are involved in the locomotor process and it is reasonable to assume that their activity contributes to the control of the movements.

Electrophysiological influences of the parietal cortex and dorso-medial thalamic nucleus on the prefrontal cortex of the cat.

Lesion studies have shown that the functional integrity of prefrontal and posterior parietal cortex is necessary for complex behavioural performance. Recordings were made from 137 prefrontal cells in awake cats. Parietal cortex stimulation affected fifty-four cells (39.5%); thirty-four (63%) increased and twenty (37%) decreased their discharge frequency. Thalamic stimulation affected forty-seven cells; twenty-eight increased their discharge and nineteen decreased it. These responses suggest firstly that the organization between parietal and prefrontal cortex is similar to that in monkeys, and secondly that prefrontal cortex has an integrative role.

Passive avoidance conditioning and unitary activity in the basolateral amygdaloid nucleus of the rat.

Single unit activity was recorded in the basolateral nucleus of amygdala in rats in a passive avoidance test. Simultaneously, visual control of exploratory behaviour was carried out. Prior to establishing the conditioning, the mean frequency of the unit discharge was 14 Hz (SD = 9) and 1 minute after conditioning this unit activity decreased to values close to zero; later on (24 and 48 hours), a progressive recovery of the discharge was observed. Behavioural changes were also detected. The long term recovery of unit activity follows the time course of the extinction process. The possible significance of these findings is discussed in relation to some of the functional roles of this nucleus.

Open field activity and passive avoidance responses in rats after lesion of the central amygdaloid nucleus by electrocoagulation and ibotenic acid.

The effect of two types of bilateral lesion of the central amygdaloid nucleus on open field activity and on the acquisition of a passive avoidance conditioning in a run way was studied in male Wistar rats. The animals were divided into three groups: sham-operated, a group with lesions caused by electrocoagulation, and a third group lesioned by local application of ibotenic acid. Ibotenic acid is a neurotoxin which damages the neurons but spares the passing fibres. The results indicate that lesion by electrocoagulation leads to a significant increase in the number of rearing responses in the open field. Moreover, lesion by electrocoagulation, but not by ibotenic acid, leads to a deficit in the acquisition of passive avoidance conditioning. This latter result suggests that the deficit is caused by lesion of the fibres crossing the central amygdaloid nucleus and not by the intrinsic elements of the nucleus.

[The effect of lesions of the anteroventral and anterodorsal thalamic nuclei on the emotional reactivity of the rat]. / Efecto de la lesión de los núcleos anteroventral y anterodorsal talámicos sobre la reactividad emocional de la rata.

The effect of anteroventral and anterodorsal thalamic nuclei lesions on emotional reactivity has been studied. The behavior of 18 rats (half of them bearing thalamic lesions) was studied by means of the open field and the acquisition of a conditioned emotional response (Estes and Skinner technique). Results show that no differences between control and experimental animals were found in exploratory behavior in the open field, where the number of defecations in each group was similar. They also show great impairment in the acquisition of a conditioned emotional response in experimental animals. These results suggest that the structures under study might be involved in the regulation of emotional reactivity.