Publications (12) View all
-
Article: Operant discriminative learning and evidence of subtelencephalic plastic changes after long-term detelencephalation in pigeons.
[show abstract] [hide abstract]
ABSTRACT: We analyzed operant discrimination in detelencephalated pigeons and neuroanatomical substrates after long-term detelencephalation. In Experiment I, experimental pigeons with massive telencephalic ablation and control pigeons were conditioned to key peck for food. Successive discrimination was made under alternating red (variable-ratio reinforcement) and yellow (extinction) lights in one key of the chamber. These relations were interchanged during reversal discrimination. The sessions were run until steady-state rates were achieved. Experiment II analyzed the morphology of the nucleus rotundus and optic tectum in long-term detelencephalated and control birds, using a Klüver-Barrera staining and image analyzer system. Detelencephalated birds had more training sessions for response shaping and steady-state behavior (p < 0.001), higher red key peck rates during discrimination (p < 0.01), and reversal discrimination indexes around 0.50. Morphometric analysis revealed a decreased number of neurons and increased vascularity, associated with increases in the perimeter (p < 0.001) in the nucleus rotundus. In the optic tectum, increases in the perimeter (p < 0.05) associated with disorganization in the layers arrangement were seen. The data indicate that telencephalic systems might have an essential function in reversal operant discrimination learning. The structural characteristics of subtelencephalic systems after long-term detelencephalation evidence plastic changes that might be related to functional mechanisms of learning and neural plasticity in pigeons.Neural plasticity. 02/2003; 10(4):247-66. -
Article: S100 immunoreactivity is increased in reactive astrocytes of the visual pathways following a mechanical lesion of the rat occipital cortex.
[show abstract] [hide abstract]
ABSTRACT: After demonstration of the paracrine action of glial neurotrophic factors, gliosis has also been considered to be related to neuronal trophism and plasticity rather than solely a repair event following brain injury. S100 is a Ca2+ binding protein, present mainly in astrocytes, that exerts paracrine trophic effects on several neuronal populations. This study analyses the presence of S100 protein by means of immunohistochemistry combined with stereology in the reactive glial cells of the rat visual pathways following a lesion of the visual cortex. Adult male Wistar rats were submitted to a unilateral aspiration of the occipital cortex or to a sham operation. One week later the rats were killed and their brain processed for immunochemistry. Single antibody immunohistochemistry was performed for the visualization of glial fibrillary acidic protein (GFAP, a marker for astrocytes), OX-42 (a marker for microglia) and S100 protein. Double immunofluorescence procedures were applied for co-localization of the S100/GFAP and S100/OX-42. An optical dissector, point interceptors and rotators were used to quantify the degree of glial activation and the changes in the S100 immunoreactivity. We observed an intense microglial and astroglial reaction in addition to an increased S100 immunoreactivity in the occipital cerebral cortex, geniculate nucleus and hippocampus ipsilateral to the lesion. In the ipsilateral superior colliculus, an intense astroglial activation was accompanied by an up-regulation of S100 immunoreactivity. Double-immunofluoresence revealed an increased S100 immunoreactivity in reactive astrocytes, but not in the reactive microglia. Evidence has therefore been obtained that after mechanical trauma, the astroglial S100 protein participates in the trophism and plasticity of the injured visual pathways.Cell Biology International 02/2000; 24(1):35-49. · 1.48 Impact Factor -
Article: The functional value of sound and exploratory behaviour in detelencephalated pigeons.
[show abstract] [hide abstract]
ABSTRACT: Exploratory behaviour in response to a sound previously paired to a shock was analyzed before and after massive telencephalic lesions. Six pigeons were submitted to sound shock associations, habituation tests, telencephalic lesion and habituation retesting. Eighteen birds divided into three sham-lesioned groups received sound shock pairing (Control 1), pre-exposure to sound stimulation (Control 2) or pre-exposure to electric shocks (Control 3) before the behavioural tests. The pre-surgery tests consisted of 25 1 s pulses of sound A (1000 Hz, 83 dB) or B (500 Hz, 85 dB), every 30 s. Retests took place 10 days after surgery using the same sequence of procedures. The behaviour exhibited immediately after each sound stimulation was recorded manually and on video during the sessions. Analysis of variance showed an effect of group {F(3, 20)= 13.37, p < 0.0001) suggesting that pre-exposure to tone-shock association affected the exploration in response to the sound presented in another context. The Experimental and Control 1 birds showed no robust decrease in responses during the pre-surgery sessions. Post-surgery exploration data for detelencephalated birds showed a lower level of responding (p < 0.05). These data suggest a retardation in the typical reduction of responses to recurrent stimulation and support other evidences of the potentiating effect of sound shock association on responding. They are also indicative of telencephalic modulation of exploratory behaviour and strengthen the arguments for the subtelencephalic storage of associative information concerning the functional value of acoustic stimulation.Behavioural Brain Research 06/1999; 101(1):93-103. · 3.42 Impact Factor -
Article: Operant discrimination learning in detelencephalated pigeons (Columba livia).
[show abstract] [hide abstract]
ABSTRACT: Operant discrimination learning was analyzed in pigeons after massive telencephalic lesions. Twenty-one pigeons were divided into three groups: non-lesioned (N = 6), sham-lesioned (N = 5) and telencephalon lesioned (N = 10). Lesion surgeries were carried out before any experimental training. Learning procedures were run in the same sequence for all groups and under a food deprivation of 80% of the ad libitum weight. Successive discrimination was programmed by the alteration of red and yellow lights in the right key of a standard operant chamber: the red key was correlated with variable-ratio reinforcement; the yellow key was correlated with extinction. Session were run until steady-state key peck rates were obtained. The following results demonstrate discrimination learning by detelencephalated birds. Response shaping and steady-state rates required a larger number of sessions for lesioned pigeons (P < 0.05). They showed increased response rates in red (26.43 +/- 2.59) and yellow (11.17 +/- 2.86) components as compared to the non-lesioned (red: 16.51 +/- 2.0; yellow: 2.02 +/- 0.64) and sham-lesioned (red: 22.84 +/- 1.77; yellow: 4.72 +/- 1.99) groups (P < 0.05). These data show that telencephalic systems are not essential for operant discrimination learning but play a role in the modulation of discriminative behavior. Subtelencephalic systems appear to be functionally important for the organization and storage of learning.Brazilian Journal of Medical and Biological Research 11/1995; 28(10):1089-95. · 1.13 Impact Factor -
Article: Neuromodulatory property of standardized extract Ginkgo biloba L. (EGb 761) on memory: behavioral and molecular evidence.
[show abstract] [hide abstract]
ABSTRACT: Although it has been suggested that the standardized Ginkgo biloba leaf extract (Egb 761) may have a beneficial effect on memory, the cellular and molecular changes that underlie this process are not yet well defined. The present study evaluated the effects of acute (one dose) or subacute treatments (one daily dose/seven days) with EGb 761 (0.5 g kg(-1) and 1.0 g kg(-1)) on rats submitted to a conditioned emotional response (CER) in comparison with positive (4 mg kg(-1) Diazepam) and negative (12%Tween 80) control groups. To this end, eighty (n=10/group) adult, male, Wistar rats (+/-250-300 g) were used in an off-baseline CER procedure. We here observed that the rats submitted to an acute and subacute EGb 761 treatments had acquisition of fear conditioning. Additionally, we investigate if the expression of genes previously associated with classical conditioning (CREB-1 and GAP-43) and new candidate genes (GFAP) are modulated following EGb 761 acute treatment. CREB-1, GAP-43 and GFAP mRNA and protein expressions were evaluated using both quantitative PCR (qPCR) and immunohistochemical analysis, respectively. We here show, for the first time, that EGb 761 modulated GAP-43, CREB-1 and GFAP expression in the prefrontal cortex, amygdala and hippocampus. We observed an underexpression of GAP-43 in all structures evaluated and over-expression of GFAP in the amygdala and hippocampus following acute G. biloba treatment when compared to control group (Tween; p<0.01). GAP-43 expression was decreased in prefrontal cortex and hippocampus in the subacute treatment with EGb 761. Subacute treatment with EGb 761 lead to a decreased CREB-1 in mPFC (p<0.001) and increased in the hippocampus to 1.0 g kg(-1)G. biloba group (p<0.001). The results obtained from immunohistochemical analysis support our aforementioned findings and revealed that the changes in expression occurred within specific regions in the areas evaluated. All together, our findings not only provide new evidence for a role of EGb 761 on memory but also identify molecular changes that underlie the fear memory consolidation.Brain research 12/2008; 1269:68-89. · 2.46 Impact Factor
