Jorge Quevedo | Dirección Nacional de Investigaciones de El Salvador (original) (raw)
Papers by Jorge Quevedo
Behavioural Pharmacology, 1998
Rats received, through bilaterally implanted indwelling cannulae, 0.5 microliter infusions of 6-c... more Rats received, through bilaterally implanted indwelling cannulae, 0.5 microliter infusions of 6-cyano-7-nitroquinoxaline2,3-dione (CNQX) (0.5 microgram), D-2-amino-5-phophono pentanoic acid (AP5) (5.0 micrograms), muscimol (0.5 microgram), scopolamine (2.0 micrograms), SCH23390 (2.5 micrograms), saline or a vehicle into the CA1 region of the hippocampus, or into the antero-lateral prefrontal (PRE), posterior parietal (PP) and entorhinal cortex (EC). The infusions were given 6 min prior to one-trial step-down inhibitory avoidance training in order to measure their effect on working memory (WM), or immediately post-training in order to measure their effect on short-term (STM) and long-term memory (LTM), 1.5 and 24 h later, respectively. WM was inhibited by CNQX or muscimol given into any of the cortical areas, by SCH23390 given into CA1, PRE or PP, and by scopolamine given into PRE or EC. STM was unaffected by any of the treatments given into PRE, and was inhibited by CNQX or muscimol given into CA1, PP and EC and by scopolamine given into PP, and enhanced by SCH given into CA1. LTM was inhibited by CNQX, muscimol, scopolamine or SCH23390 given into PRE, by scopolamine given into PP, by SCH23390 given into the entorhinal cortex, and by AP5, CNQX, muscimol or scopolamine given into CA1. The results indicate a differential involvement of the various neurotransmitter systems in the three types of memory in the various brain areas, and a separation of the mechanisms and of the regions involved in each. In addition, some of the findings suggested links between WM and LTM processing in PRE, between WM and STM processing in EC and PP, and between all three types of memory in CA1.
European Journal of Neuroscience, 1997
The hippocampus and amygdala, the entorhinal cortex and the parietal cortex participate, in that ... more The hippocampus and amygdala, the entorhinal cortex and the parietal cortex participate, in that sequence, both in the formation and in the expression of memory for a step-down inhibitory avoidance task in rats. Bilateral infusion of AP5 or muscimol caused retrograde amnesia when given O min after training into both hippocampus and amygdala, when given or 180 min after training into the entorhinal cortex, or when given 180 min after training into the parietal cortex. Therefore, memory formation requires the sequential and integrated activity of all these areas mediated by glutamate NMDA receptors in each case. Pre-test administration of CNQX 1 day after training into hippocampus and amygdala, 1 or 31 days after training in entorhinal cortex, or 1, 31 or 60 days after training in the parietal cortex temporarily blocked retention test performance. Therefore, 1 day after training, all these brain structures are necessary for retrieval; 1 month later, the hippocampus and amygdala are no longer necessary for retrieval but the entorhinal and parietal cortex still are; and 60 days after training only the parietal cortex is needed. In all cases the mechanisms of retrieval require intact glutamate AMPA receptors.
Behavioural Pharmacology, 1996
Rats bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus and/or in th... more Rats bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus and/or in the amygdaloid nucleus, in the entorhinal cortex, and in the posterior parietal cortex, were trained in a step-down inhibitory avoidance task. At various times after training (immediately, 30, 60 or 90min) they received, through the cannulae, 0.5µl microinfusions of saline or of 5.0µg of AP5 dissolved in saline. A retention test was carried out 24h after training. Retention test performance was hindered by AP5 given into hippocampus, amygdala, or both hippocampus and amygdala immediately but not 30min post-training. The drug was amnestic when given into the entorhinal cortex 30, 60 or 90min after training, or into the parietal cortex 60 or 90min after training, but not at earlier times. The findings suggest a sequential entry in operation, in the post-training period, of NMDA-receptor mediated mechanisms involved in memory processing; first in hippocampus and amygdala, 30min later in entorhinal cortex, and 30min later in posterior parietal cortex.
Annals of The New York Academy of Sciences, 1998
T he phasic modulation of the H-reflex during human locomotion 1 and the rhythmic fluctuations of... more T he phasic modulation of the H-reflex during human locomotion 1 and the rhythmic fluctuations of intraaxonally recorded primary afferent depolarizations 2 during fictive locomotion in cats suggest a cyclic presynaptic inhibition of group Ia afferents and hence a modulation of synaptic efficacy during locomotion. In the present study, the amplitudes of Ia monosynaptic EPSPs were measured in lumbar motoneurons to directly determine whether locomotion is associated with a reduction in neurotransmitter release from group I afferent terminals during fictive locomotion. Fictive locomotion was evoked by mesencephalic locomotor region (MLR) stimulation in decerebrate cats paralyzed with a neuromuscular blocker (see ref.
Annals of The New York Academy of Sciences, 1998
I n the absence of locomotion, activation of extensor muscle spindle (Ia) and tendon organ (Ib) a... more I n the absence of locomotion, activation of extensor muscle spindle (Ia) and tendon organ (Ib) afferents evokes a widespread pattern of interneuronally mediated inhibition and excitation through the nonreciprocal reflex systems. 1 During the extension phase of fictive locomotion, however, the same afferents evoke a disynaptic excitation of extensor motoneurons. Recently it has been reported that stimulation of flexor group I afferents also evokes a locomotor-dependent excitation of ankle flexor motoneurons. The present study further examined the distribution of locomotor-dependent group I excitation of flexor motoneurons and extended the analysis to motoneurons showing complex patterns of depolarization during locomotion, that is, motoneurons innervating bifunctional muscles. Intracellular recordings of antidromically identified motoneurons were made (using glass microelectrodes filled with QX-314 to block action potentials) in decerebrate cats in which fictive locomotion was elicited by brainstem stimulation following neuromuscular blockade (see reference 2).
Annals of The New York Academy of Sciences, 1998
C ontact between the dorsum of a hindlimb paw and an obstacle during the swing phase of locomotio... more C ontact between the dorsum of a hindlimb paw and an obstacle during the swing phase of locomotion evokes a specific pattern of muscle activation in an attempt to avoid tripping. This pattern has been termed the stumbling corrective reaction 1 and consists of a cessation of activity in ankle flexor muscles and an onset of activity in knee flexors and the ankle extensor, lateral gastrocnemius. As a result of the ankle extension, the forward motion of the foot can continue and as a result of the knee flexion, the foot is raised to clear the obstacle. 1-4 Stumbling correction has been described during treadmill walking in intact, for example, and chronic spinal 2 cats and in man. 5,6 Its presence in spinal animals indicates that the response can be organized at the level of the lumbar spinal cord. Because the stumbling corrective reaction is abolished by anesthesia of the skin, 2,3 cutaneous receptors appear essential. On the other hand, because electrical stimulation of the skin does not evoke stumbling correction, 3,4 it has been suggested that participation of proprioceptors is also required for the response. The present experiments were designed to address two questions: Can the stumbling corrective reaction be evoked during fictive locomotion, and can it be evoked by cutaneous stimulation alone? Observations were obtained during fictive locomotion produced by stimulation of the midbrain in decerebrate cats following neuromuscular blockade (see reference 7 for details).The superficial peroneal (SP) nerve containing the cutaneous innervation of the dorsum of the foot was stimulated using a train of 20-40 shocks (200 Hz) at twice threshold. Rectified, integrated, electroneurogram (ENG) activity was used as a monitor of fictive locomotion and using a window discriminator, to trigger the delivery of the stimulus train during a particular part of the fictive locomotor step cycle. FIGURE 1 shows an average of 14 trials in which the SP nerve was stimulated about 200 ms after the onset of activity in the tibialis anterior (ankle flexor) nerve. The traces are aligned at the onset of stimulus delivery (vertical dashed line). Shortly after the beginning of the stimulus train there is upward deflection of the TA ENG indicating an excitation of TA, motoneurons, which is quickly followed by a reduction in TA activity to below prestimulus levels. Posterior biceps (PB) and semitendinosus (St) are activated soon after stimulus onset and a few milliseconds later, activity in lateral gastrocnemius and soleus (LGS) appears. The sequence of a sustained excitation of knee (PB and St) but not ankle (TA) flexors and the delayed excitation of ankle extensors (LGS), and the latencies of these responses are remarkably similar to those reported during treadmill locomotion in intact cats (e.g., reference 3, figure 3). Although intracellular records and accurate determination of the arrival of the volley at the spinal cord are needed to determine the minimum intraspinal latency of TA, PB, and St excitation, the 7.3-ms latency from the onset of stimulation illustrated in FIGURE 1 includes 502 a This work was supported by the Canadian MRC and the Rick Hansen Legacy Fund.
Water distribution systems generally consist of a number of sources of supply from which water is... more Water distribution systems generally consist of a number of sources of supply from which water is pumped to storage reservoirs to meet demands at consumer nodes through interconnected pipeline networks. Pressure levels and water transfers between different zones of a network are governed by control elements such as pumps, valves or turbines, which may be operated from a central dispatch. Operation costs are primarily related to the supply and treatment costs from the different sources and to the pumping energy expenses which depend on variable electricity tariffs. The optimization of the operation of such systems seeks to derive, ahead in time, the best strategies for the control elements, in order to minimize the overall costs for an operation period, while keeping a satisfactory service to consumers. The optimization methods applicable to this kind of problem must cater for high dimensionality as well as constraints on both states and controls. This work deals with the development of a programme for optimization of the operation in the network of Barcelona, through the use of a projected conjugate gradient method. Firstly, the characteristics of the real system are described and the modelling assumptions are summarized. Then, the optimization method is reported and the results of its application to the real system are presented.
Behavioural Pharmacology, 1998
Rats received, through bilaterally implanted indwelling cannulae, 0.5 microliter infusions of 6-c... more Rats received, through bilaterally implanted indwelling cannulae, 0.5 microliter infusions of 6-cyano-7-nitroquinoxaline2,3-dione (CNQX) (0.5 microgram), D-2-amino-5-phophono pentanoic acid (AP5) (5.0 micrograms), muscimol (0.5 microgram), scopolamine (2.0 micrograms), SCH23390 (2.5 micrograms), saline or a vehicle into the CA1 region of the hippocampus, or into the antero-lateral prefrontal (PRE), posterior parietal (PP) and entorhinal cortex (EC). The infusions were given 6 min prior to one-trial step-down inhibitory avoidance training in order to measure their effect on working memory (WM), or immediately post-training in order to measure their effect on short-term (STM) and long-term memory (LTM), 1.5 and 24 h later, respectively. WM was inhibited by CNQX or muscimol given into any of the cortical areas, by SCH23390 given into CA1, PRE or PP, and by scopolamine given into PRE or EC. STM was unaffected by any of the treatments given into PRE, and was inhibited by CNQX or muscimol given into CA1, PP and EC and by scopolamine given into PP, and enhanced by SCH given into CA1. LTM was inhibited by CNQX, muscimol, scopolamine or SCH23390 given into PRE, by scopolamine given into PP, by SCH23390 given into the entorhinal cortex, and by AP5, CNQX, muscimol or scopolamine given into CA1. The results indicate a differential involvement of the various neurotransmitter systems in the three types of memory in the various brain areas, and a separation of the mechanisms and of the regions involved in each. In addition, some of the findings suggested links between WM and LTM processing in PRE, between WM and STM processing in EC and PP, and between all three types of memory in CA1.
European Journal of Neuroscience, 1997
The hippocampus and amygdala, the entorhinal cortex and the parietal cortex participate, in that ... more The hippocampus and amygdala, the entorhinal cortex and the parietal cortex participate, in that sequence, both in the formation and in the expression of memory for a step-down inhibitory avoidance task in rats. Bilateral infusion of AP5 or muscimol caused retrograde amnesia when given O min after training into both hippocampus and amygdala, when given or 180 min after training into the entorhinal cortex, or when given 180 min after training into the parietal cortex. Therefore, memory formation requires the sequential and integrated activity of all these areas mediated by glutamate NMDA receptors in each case. Pre-test administration of CNQX 1 day after training into hippocampus and amygdala, 1 or 31 days after training in entorhinal cortex, or 1, 31 or 60 days after training in the parietal cortex temporarily blocked retention test performance. Therefore, 1 day after training, all these brain structures are necessary for retrieval; 1 month later, the hippocampus and amygdala are no longer necessary for retrieval but the entorhinal and parietal cortex still are; and 60 days after training only the parietal cortex is needed. In all cases the mechanisms of retrieval require intact glutamate AMPA receptors.
Behavioural Pharmacology, 1996
Rats bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus and/or in th... more Rats bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus and/or in the amygdaloid nucleus, in the entorhinal cortex, and in the posterior parietal cortex, were trained in a step-down inhibitory avoidance task. At various times after training (immediately, 30, 60 or 90min) they received, through the cannulae, 0.5µl microinfusions of saline or of 5.0µg of AP5 dissolved in saline. A retention test was carried out 24h after training. Retention test performance was hindered by AP5 given into hippocampus, amygdala, or both hippocampus and amygdala immediately but not 30min post-training. The drug was amnestic when given into the entorhinal cortex 30, 60 or 90min after training, or into the parietal cortex 60 or 90min after training, but not at earlier times. The findings suggest a sequential entry in operation, in the post-training period, of NMDA-receptor mediated mechanisms involved in memory processing; first in hippocampus and amygdala, 30min later in entorhinal cortex, and 30min later in posterior parietal cortex.
Annals of The New York Academy of Sciences, 1998
T he phasic modulation of the H-reflex during human locomotion 1 and the rhythmic fluctuations of... more T he phasic modulation of the H-reflex during human locomotion 1 and the rhythmic fluctuations of intraaxonally recorded primary afferent depolarizations 2 during fictive locomotion in cats suggest a cyclic presynaptic inhibition of group Ia afferents and hence a modulation of synaptic efficacy during locomotion. In the present study, the amplitudes of Ia monosynaptic EPSPs were measured in lumbar motoneurons to directly determine whether locomotion is associated with a reduction in neurotransmitter release from group I afferent terminals during fictive locomotion. Fictive locomotion was evoked by mesencephalic locomotor region (MLR) stimulation in decerebrate cats paralyzed with a neuromuscular blocker (see ref.
Annals of The New York Academy of Sciences, 1998
I n the absence of locomotion, activation of extensor muscle spindle (Ia) and tendon organ (Ib) a... more I n the absence of locomotion, activation of extensor muscle spindle (Ia) and tendon organ (Ib) afferents evokes a widespread pattern of interneuronally mediated inhibition and excitation through the nonreciprocal reflex systems. 1 During the extension phase of fictive locomotion, however, the same afferents evoke a disynaptic excitation of extensor motoneurons. Recently it has been reported that stimulation of flexor group I afferents also evokes a locomotor-dependent excitation of ankle flexor motoneurons. The present study further examined the distribution of locomotor-dependent group I excitation of flexor motoneurons and extended the analysis to motoneurons showing complex patterns of depolarization during locomotion, that is, motoneurons innervating bifunctional muscles. Intracellular recordings of antidromically identified motoneurons were made (using glass microelectrodes filled with QX-314 to block action potentials) in decerebrate cats in which fictive locomotion was elicited by brainstem stimulation following neuromuscular blockade (see reference 2).
Annals of The New York Academy of Sciences, 1998
C ontact between the dorsum of a hindlimb paw and an obstacle during the swing phase of locomotio... more C ontact between the dorsum of a hindlimb paw and an obstacle during the swing phase of locomotion evokes a specific pattern of muscle activation in an attempt to avoid tripping. This pattern has been termed the stumbling corrective reaction 1 and consists of a cessation of activity in ankle flexor muscles and an onset of activity in knee flexors and the ankle extensor, lateral gastrocnemius. As a result of the ankle extension, the forward motion of the foot can continue and as a result of the knee flexion, the foot is raised to clear the obstacle. 1-4 Stumbling correction has been described during treadmill walking in intact, for example, and chronic spinal 2 cats and in man. 5,6 Its presence in spinal animals indicates that the response can be organized at the level of the lumbar spinal cord. Because the stumbling corrective reaction is abolished by anesthesia of the skin, 2,3 cutaneous receptors appear essential. On the other hand, because electrical stimulation of the skin does not evoke stumbling correction, 3,4 it has been suggested that participation of proprioceptors is also required for the response. The present experiments were designed to address two questions: Can the stumbling corrective reaction be evoked during fictive locomotion, and can it be evoked by cutaneous stimulation alone? Observations were obtained during fictive locomotion produced by stimulation of the midbrain in decerebrate cats following neuromuscular blockade (see reference 7 for details).The superficial peroneal (SP) nerve containing the cutaneous innervation of the dorsum of the foot was stimulated using a train of 20-40 shocks (200 Hz) at twice threshold. Rectified, integrated, electroneurogram (ENG) activity was used as a monitor of fictive locomotion and using a window discriminator, to trigger the delivery of the stimulus train during a particular part of the fictive locomotor step cycle. FIGURE 1 shows an average of 14 trials in which the SP nerve was stimulated about 200 ms after the onset of activity in the tibialis anterior (ankle flexor) nerve. The traces are aligned at the onset of stimulus delivery (vertical dashed line). Shortly after the beginning of the stimulus train there is upward deflection of the TA ENG indicating an excitation of TA, motoneurons, which is quickly followed by a reduction in TA activity to below prestimulus levels. Posterior biceps (PB) and semitendinosus (St) are activated soon after stimulus onset and a few milliseconds later, activity in lateral gastrocnemius and soleus (LGS) appears. The sequence of a sustained excitation of knee (PB and St) but not ankle (TA) flexors and the delayed excitation of ankle extensors (LGS), and the latencies of these responses are remarkably similar to those reported during treadmill locomotion in intact cats (e.g., reference 3, figure 3). Although intracellular records and accurate determination of the arrival of the volley at the spinal cord are needed to determine the minimum intraspinal latency of TA, PB, and St excitation, the 7.3-ms latency from the onset of stimulation illustrated in FIGURE 1 includes 502 a This work was supported by the Canadian MRC and the Rick Hansen Legacy Fund.
Water distribution systems generally consist of a number of sources of supply from which water is... more Water distribution systems generally consist of a number of sources of supply from which water is pumped to storage reservoirs to meet demands at consumer nodes through interconnected pipeline networks. Pressure levels and water transfers between different zones of a network are governed by control elements such as pumps, valves or turbines, which may be operated from a central dispatch. Operation costs are primarily related to the supply and treatment costs from the different sources and to the pumping energy expenses which depend on variable electricity tariffs. The optimization of the operation of such systems seeks to derive, ahead in time, the best strategies for the control elements, in order to minimize the overall costs for an operation period, while keeping a satisfactory service to consumers. The optimization methods applicable to this kind of problem must cater for high dimensionality as well as constraints on both states and controls. This work deals with the development of a programme for optimization of the operation in the network of Barcelona, through the use of a projected conjugate gradient method. Firstly, the characteristics of the real system are described and the modelling assumptions are summarized. Then, the optimization method is reported and the results of its application to the real system are presented.