Salvador Almazan-Alvarado - Academia.edu (original) (raw)

Papers by Salvador Almazan-Alvarado

Brain Stimulation, 2019

Background: Variation in the temporal patterns of electrical pulses in stimulation trains has ope... more Background: Variation in the temporal patterns of electrical pulses in stimulation trains has opened a new field of opportunity for the treatment of neurological disorders, such as pharmacoresistant temporal lobe epilepsy. Whether this novel type of stimulation affects epileptogenesis remains to be investigated. Objective: The purpose of this study was to analyze the effects of temporally irregular deep brain stimulation on kindling-induced epileptogenesis in rats. Methods: Temporally irregular deep brain stimulation was delivered at different times with respect to the kindling stimulation. Behavioral and electrographic changes on kindling acquisition were compared with a control group and a temporally regular deep brain stimulation-treated group. The propagation of epileptiform activity was analyzed with wavelet cross-correlation analysis, and interictal epileptiform discharge ratios were obtained. Results: Temporally irregular deep brain stimulation delivered in the epileptogenic focus during the interictal period shortened the daily afterdischarge duration, slowed the progression of seizure stages, diminished the generalized seizure duration and interfered with the propagation of epileptiform activity from the seizure onset zone to the ipsi-and contralateral motor cortex. We also found a negative correlation between seizure severity and interictal epileptiform discharges in rats stimulated with temporally irregular deep brain stimulation. Conclusion: These results provide evidence that temporally irregular deep brain stimulation interferes with the establishment of epilepsy by delaying epileptogenesis by almost twice as long in kindling animals. Thus, temporally irregular deep brain stimulation could be a preventive approach against epilepsy.

Neuroscience, 2017

Dysfunction of thalamo-cortical networks involving particularly the thalamic reticular nucleus (T... more Dysfunction of thalamo-cortical networks involving particularly the thalamic reticular nucleus (TRN) is implicated in schizophrenia. In the neonatal ventral hippocampal lesion (NVHL), a heuristic animal model of schizophrenia, brain oscillation changes similar to those of schizophrenic patients have been reported. The aim of this study was to analyze the effects of short-term deep brain stimulation (DBS) in the thalamic reticular nucleus on electroencephalographic (EEG) activity in the NVHL. Male and female Sprague-Dawley rats were used and the model was prepared by excitotoxicity damage of the ventral hippocampus on postnatal day 7 (PD-7). Chronic bilateral stainless steel electrodes were implanted in the TRN, thalamic dorsomedial nucleus and prelimbic area at PD-90. Rats were classified as follows: sham and NVHL groups, both groups received bilateral DBS in the TRN for one hour (100Hz, 100µs pulses, 200µA). All animals showed a sudden behavioral arrest accompanied by widespread symmetric bilateral spike-wave discharges, this activity was affected by DBS-TRN. Additionally, the power spectra of 0.5-100Hz and the coherence of 0.5-4.5 and 35-55Hz frequencies were modified by DBS-TRN. Our results suggest that DBS in the TRN may modify functional connectivity between different parts of the thalamo-cortical network. Additionally, our findings may suggest a beneficial effect of DBS-TRN on some preclinical aberrant oscillatory activities in a neurodevelopmental model of schizophrenia.

Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, Jan 24, 2017

Justicia spicigera Schltdl. is a vegetal species traditionally used to control epilepsy, but scie... more Justicia spicigera Schltdl. is a vegetal species traditionally used to control epilepsy, but scientific evidence is required to reinforce this activity. The aim of the study was to evaluate the anticonvulsant-like activity of J. spicigera aqueous extract (JsAE) and a bioactive compound. JsAE was assessed in a dose-response manner (30, 100 and 1000mg/kg, i.p.) using the pentylenetetrazol (PTZ)-induced seizures and maximal electroshock seizure (MES) test in mice in comparison to ethosuximide (ETX, reference drug 100mg/kg, i.p.) or phenytoin (25mg/kg, i.p.), respectively. Then a significant dosage (1000mg/kg, i.p.) was chosen to examine electrographic activity (EEG) in rats. Treatment groups were compared to the vehicle and ETX in the convulsive behavior alone or simultaneous to EEG after PTZ-induced seizures (80 or 35mg/kg, i.p., mice or rats). Kaempferitrin (a flavonoid of JsAE) and ETX were administered via intracerebroventricular (i.c.v, 4th ventricle, 1μg/μL) and tested in the pre...

Epilepsy & Behavior, 2013

Noninvasive transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrod... more Noninvasive transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrodes (TCREs) has been under development as an alternative/complementary therapy for seizure control. Transcranial focal electrical stimulation has shown efficacy in attenuating penicillin-, pilocarpine-, and pentylenetetrazole-induced acute seizures in rat models. This study evaluated the effects of TFS via TCREs on the memory formation of healthy rats as a safety test of TFS. Short-and long-term memory formation was tested after the application of TFS using the novel object recognition (NOR) test. The following independent groups were used: naïve, control (without TFS), and TFS (treated). The naïve, control, and stimulated groups spent more time investigating the new object than the familiar one during the test phase. Transcranial focal electrical stimulation via TCREs given once does not modify the short-and long-term memory formation in rats in the NOR test. Results provide an important step towards a better understanding for the safe usage of TFS via TCREs.

Brain Stimulation, 2014

Background: Deep brain stimulation, specifically high-frequency stimulation (HFS), is an alternat... more Background: Deep brain stimulation, specifically high-frequency stimulation (HFS), is an alternative and promising treatment for intractable epilepsies; however, the optimal targets are still unknown. The thalamic reticular nucleus (TRN) occupies a key position in the modulation of the cortico-thalamic and thalamo-cortical pathways. Objective: We determined the efficacy of HFS in the TRN against tonic-clonic generalized seizures (TCGS) and status epilepticus (SE), which were induced by scheduled pentylenetetrazole (PTZ) injections. Methods: Male Wistar rats were stereotactically implanted and assigned to three experimental groups: Control group, which received only PTZ injections; HFS-TRN group, which received HFS in the left TRN prior to PTZ injections; and HFS-Adj group, which received HFS in the left adjacent nuclei prior to PTZ injections. Results: The HFS-TRN group reported a significant increase in the latency for development of TCGS and SE compared with the HFS-Adj and Control groups (P < 0.009). The number of PTZ-doses required for SE was also significantly increased (P < 0.001). Spectral analysis revealed a significant decrease in the frequency band from 0.5 Hz to 4.5 Hz of the left motor cortex in the HFS-TRN and HFS-Adj groups, compared to the Control group. Conversely, HFS-TRN provoked a significant increase in all frequency bands in the TRN. EEG asynchrony was observed during spike-wave discharges by HFS-TRN. Conclusion: These data indicate that HFS-TRN has an anti-epileptogenic effect and is able to modify seizure synchrony and interrupt abnormal EEG recruitment of thalamo-cortical and, indirectly, corticothalamic pathways.

Epilepsia, 2002

This work analyzed the effect of electrical stimulation of the nucleus of the solitary tract (NTS... more This work analyzed the effect of electrical stimulation of the nucleus of the solitary tract (NTS) on the development of electrical amygdaloid kindling (AK) in freely moving cats. Methods: Nine male adult cats with implanted electrodes in both amygdalae (basolateral nucleus), both lateral geniculate bodies, left NTS, and both prefrontal cortices were used. Electromyogram and electrooculogram also were recorded. The AK was performed every 24 h (1-s train, 1-ms pulses, 60 Hz, 300-600 A). The NTS was stimulated previously for 1 min (0.5ms pulses, 30 Hz, 150-300 A), just before the AK at 10:00 a.m., and then every 60 min, 4 times, from 11:00 a.m. to 2:00 p.m. On different days, all NTS stimulation was suspended, and AK was continued until stage VI kindling was reached. Results: Behavioral changes produced by the stimulation of the NTS were blinking, immobility periods with upward sight, licking, and swallowing. Animals with simultaneous stimula

Behavioural Brain Research, 2016

Deep brain stimulation (DBS) is used as an alternative therapeutic procedure for pharmacoresistan... more Deep brain stimulation (DBS) is used as an alternative therapeutic procedure for pharmacoresistant psychiatric disorders. Recently the thalamic reticular nucleus (TRN) gained attention due to the description of a novel pathway from the amygdala to this nucleus suggesting that may be differentially disrupted in mood disorders. The limbic system is implicated in the regulation of these disorders that are accompanied by neuroplastic changes. The hippocampus is highly plastic and shows the generation of new neurons, process affected by stress but positively regulated by antidepressant drugs. We explored the impact of applying acute DBS to the TRN (DBS-TRN) in male Wistar rats exposed to acute stress caused by the forced-swim Porsolt&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s test (FST) and on initial events of hippocampal neurogenesis. After the first session of forced-swim, rats were randomly subdivided in a DBS-TRN and a Sham group. Stimulated rats received 10min of DBS, thus the depressant-like behavior reflected as immobility was evaluated in the second session of forced-swim. Locomotricity was evaluated in the open field test. Cell proliferation and doublecortin-associated cells were quantified in the hippocampus of other cohorts of rats. No effects of electrode implantation were found in locomotricity. Acute DBS-TRN reduced immobility in comparison to the Sham group (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). DBS-TRN increased cell proliferation (Ki67 or BrdU-positive cells; p=0.02, p=0.02) and the number of doublecortin-cells compared to the Sham group (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.02). Similar effects were found in rats previously exposed to the first session of forced-swim. Our data could suggest that TRN brain region may be a promising target for DBS to treat intractable depression.

Synapse, 2012

A neonatal ventral hippocampal lesion (NVHL) in rats has been commonly used as a neurodevelopment... more A neonatal ventral hippocampal lesion (NVHL) in rats has been commonly used as a neurodevelopmental model to mimic schizophrenia-like behaviors. Recently, we reported that NVHL resulted in dendritic retraction and spine loss in pyramidal neurons of the prefrontal cortex (PFC). In addition, the hippocampus and PFC are important structures in the regulation of the electroencephalographic (EEG) activity. Patients with PFC lesions show deficits in the EEG activity. This study aimed to determine whether the EEG activity was altered in NVHL rats. In addition, we also analyzed the locomotor activity induced by a novel environment and exploratory behavior using the hole-board test. Consistent with the behavioral findings, the EEG analysis of the cortical regions showed that the NVHL rats displayed a lower power in cortical bands. At 1-8 Hz, 9-14 Hz, and 15-30 Hz bands, our findings showed a decrease in the absolute power of the parietal and occipital cortices recordings. In addition, the NVHL rats also showed a reduction in the exploratory behavior tested using the hole-board test. In conclusion, this study demonstrated that the EEG activity was reduced in adult NVHL rats and suggests that this may play a role in the behavioral changes observed in this neurodevelopmental model of schizophrenia. Synapse 66:738-746, 2012. V V C 2012 Wiley Periodicals, Inc.

Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2002

The effect of electrical vagus nerve stimulation (VNS) on sleep and behavior was analyzed in free... more The effect of electrical vagus nerve stimulation (VNS) on sleep and behavior was analyzed in freely moving cats. Eight cats were prepared for 23-h sleep recordings. The left vagus nerve of four of them was stimulated during 1 min, five times at 1-h intervals, for 5 days. The VNS induces: ipsilateral myosis, blinking, licking, abdominal contractions, upward gaze, swallowing, and eventually yawning and compulsive eating, as well as an increase of ponto-geniculate -occipital (PGO) wave density and of the number of stages and total amount of rapid eye movement (REM) sleep. Besides, there was a sudden transition from waking stage to REM sleep. The present results suggest that VNS modifies sleep in the cat. This effect could be explained by an activation of the areas involved in the physiological mechanisms of sleep. D

Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2008

We previously reported the effect of vagus nerve electrical stimulation (VNS) on sleep and behavi... more We previously reported the effect of vagus nerve electrical stimulation (VNS) on sleep and behavior in cats. The aim of the present study is to analyze the long-term effects of VNS on the electroencephalographic (EEG) power spectrum and on the different stages of the sleep-wakefulness cycle in the freely moving cat. To achieve this, six male cats were implanted with electrodes on the left vagal nerve and submitted to 15 rounds of 23 h continuous sleep recordings in three categories: baseline (BL), VNS and post-stimulus recording (PSR). The following parameters were analyzed: EEG power spectrum, total time and number of sleep phases, ponto-geniculo-occipital (PGO) wave density of the rapid eye movement (REM) sleep, and the number of times the narcoleptic reflex was present (sudden transition from wakefulness to REM sleep). Significant changes were detected, such as an enhancement of slow-wave sleep (SWS) stage II; a power increase in the bands corresponding to sleep spindles (8-14 Hz) and delta waves (1-4 Hz) with VNS and PSR; an increase in the total time, number of stages, and density of PGO wave in REM sleep with VNS; a decrease of wakefulness in PSR, and the eventual appearance of the narcoleptic reflex with VNS. The results show that the effect of the VNS changes during different stages of the sleep-wakefulness cycle. In REM sleep, the effect was present only during VNS, while the SWS II was affected beyond VNS periods. This suggests that ponto-medullar and thalamic mechanisms of slow EEG activity may be due to plastic changes elicited by vagal stimulation.

Epilepsy Research, 2014

Vagus nerve stimulation (VNS) is an adjunctive therapy for treating pharmacoresistant epilepsy. T... more Vagus nerve stimulation (VNS) is an adjunctive therapy for treating pharmacoresistant epilepsy. The present study analyze the effect of VNS on the epileptic activity of amygdala kindling (AK) in different seizure severity stages in freely moving cats. Fourteen adult male cats were used and were stereotaxically implanted in both amygdalae, in thalamic reticular nuclei and in prefrontal cortices. AK was developed by the application of 60 Hz pulse trains that were one second in duration. VNS was applied the following day after the first stages were reached. This stimulation consisted of 10 pulse trains in the one-hour period (1 min on/5 min off) prior to AK. AK stimulation continued until all animals reached stage VI. The behavioral changes induced by VNS were transient and bearable. The animals showed relaxation of the nictitating membrane, ipsilateral anisocoria, swallowing and licking. Intermittent VNS application in stage I induced a delay in AK progression. The effect of VNS on the amygdala afterdischarge duration (AD) did not change progressively. VNS in stages II, III, and IV does not have an inhibitory effect on AK, and the AD further exhibited a progressive development. At the end of the generalized seizures, the animals presented with synchronized bilateral discharges of the spike-wave type (3 Hz) and a behavioral ''staring spell''. Our results show that VNS applied during the different stages of seizure severity exerts an anti-epileptogenic effect in stage I but no anti-epileptogenic effect in stages II, III, and IV. These results suggest that VNS applied at stage I of kindling induces a delay of generalized convulsive activity.

Epilepsia, 2010

The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The ai... more The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The aim of this study was to analyze the preemptive effect of NTS electrical stimulation on daily amygdaloid kindling (AK) in freely moving cats. Seven adult male cats were used. Bipolar electrodes were stereotaxically implanted into both amygdalae, lateral geniculate bodies, hippocampi, and prefrontal cortices. In addition, a bipolar stainless steel electrode was implanted in the left NTS. Cats were recorded under the following experimental conditions: The NTS was stimulated for 6 days before the initiation of AK (1 min on/5 min off, 1 h total). AK was performed by stimulating the amygdala every 24 h (1 s, 60 Hz, 1 ms) until behavioral stage VI was reached. The number of stimulations to reach stage VI in control animals was 23.4 +/- 3.7, in lateral tegmental field (LTF) animals was 17.0 +/- 2.1 days. Animals subjected to preemptive NTS stimulation showed a significant increase (53.8 +/- 5.9). In addition, behavioral development was retarded, with an increase in the number of stimulations required to reach stage III. In this group, overall kindling development was delayed, and amygdaloid afterdischarge duration did not show a progressive increase as was observed in the control group. Our results indicate that preemptive NTS electrical stimulation interferes with epileptogenesis. This anticonvulsive effect could be related to the activation of certain structures that inhibit seizure development. Therefore, results suggest that NTS mediates the anticonvulsive effect of vagus nerve stimulation.

Behavioural Brain Research, 2009

The vagus nerve participates in the control and regulation of important autonomous functions, emo... more The vagus nerve participates in the control and regulation of important autonomous functions, emotional tasks, and neural activity. Electrical vagus nerve stimulation (VNS) is an approved procedure for the treatment of refractory epilepsy in humans. VNS has also been shown to improve mood complaints and cognitive function in both human patients and animals. Thus, the purpose of this study was to analyse and describe the effects of VNS on the development and establishment of sensory habituation and electrographic activity of the visual pathway in freely moving cats. Six cats had implants placed in the optic chiasm (OC), lateral geniculate body (LGB), mesencephalic reticular formation (MRF), primary visual cortex (VC) of the left hemisphere, and left vagus nerve. Immediately after surgery, all cats presented anisocoria and relaxation of the left nictitant membrane. Also showed vegetative-type responses such as myosis, licking, and swallowing during VNS. Animals were then subjected to repeated luminous stimuli at intervals of 1 and 3 s to cause habituation. The effect of VNS on the frequency and latency of the habituation episodes and the electrographic changes in the registered brain structures were analysed. Latency analysis showed that VNS delayed the first habituation episode. VNS had transitory effects on the neural activity of the primary visual pathway structures, which caused a small but measurable delay in the establishment of habituation. In conclusion, VNS interferes with the development and establishment of visual habituation, an elementary form of non-associative learning, in freely moving cats.

Salud mental, 2009

Han pasado ya cinco años desde el fallecimiento de Augusto. Su paso por la vida dejó una gran can... more Han pasado ya cinco años desde el fallecimiento de Augusto. Su paso por la vida dejó una gran cantidad de recuerdos, enseñanzas, memorias y tertulias que reflejaban su experiencia y cultura en diversos temas. Era uno de esos raros científicos que no se dedicaban a un tema en específico, sino que creía que la ciencia impone una obligación inherente de tener una idea de amplio espectro de los temas circundantes al de su especialidad. Hacer una biografía completa o un homenaje a nuestro querido Augusto sale de nuestro alcance. Los que coincidieron con él en gran parte de su trayectoria tienen herramientas para hacer una aproximación biográfica completa, muchos de nosotros hemos compartido un breve trecho de tiempo, espacio y trabajo, lo que resulta nimio en una vida larga, no sólo cronológicamente, sino sobre todo por su prolífica y brillante carrera. Respecto a un homenaje, él nunca fue entusiasta partidario de éstos cuando eran para sí.