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We present a flora and fauna dataset for the Mira-Mataje binational basins. This is an area shared between southwestern Colombia and northwestern Ecuador, where both the Chocó and Tropical Andes biodiversity hotspots converge. We systematized data from 120 sources in the Darwin Core Archive (DwC-A) standard and geospatial vector data format for geographic information systems (GIS) (shapefiles). Sources included natural history museums, published literature, and citizen science repositories across 13 countries. The resulting database has 33,460 records from 6,821 species, of which 540 have been recorded as endemic, and 612 as threatened. The diversity represented in the dataset is equivalent to 10% of the total plant species and 26% of the total terrestrial vertebrate species in both hotspots. The dataset can be used to estimate and compare biodiversity patterns with environmental parameters and provide value to ecosystems, ecoregions, and protected areas. The dataset is a baseline for future assessments of biodiversity in the face of environmental degradation, climate change, and accelerated extinction processes.
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Biodiversidad , Plantas , Ecuador , Animales , Colombia , Vertebrados , Sistemas de Información Geográfica , Ecosistema , Cambio Climático , Conservación de los Recursos Naturales , Clima TropicalRESUMEN
The analysis of the topography of brain neuromodulation following transcranial alternating current (AC) stimulation is relevant for defining strategies directed to specific nuclei stimulation in patients. Among the different procedures of AC stimulation, temporal interference (tTIS) is a novel method for non-invasive neuromodulation of specific deep brain targets. However, little information is currently available about its tissue effects and its activation topography in in vivo animal models. After a single session (30 min, 0.12 mA) of transcranial alternate current (2,000 Hz; ES/AC group) or tTIS (2,000/2,010 Hz; Es/tTIS group) stimulation, rat brains were explored by whole-brain mapping analysis of c-Fos immunostained serial sections. For this analysis, we used two mapping methods, namely density-to-color processed channels (independent component analysis (ICA) and graphical representation (MATLAB) of morphometrical and densitometrical values obtained by density threshold segmentation. In addition, to assess tissue effects, alternate serial sections were stained for glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba1), and Nissl. AC stimulation induced a mild superficial increase in c-Fos immunoreactivity. However, tTIS stimulation globally decreased the number of c-Fos-positive neurons and increased blood brain barrier cell immunoreactivity. tTIS also had a stronger effect around the electrode placement area and preserved neuronal activation better in restricted areas of the deep brain (directional stimulation). The enhanced activation of intramural blood vessels' cells and perivascular astrocytes suggests that low-frequency interference (10 Hz) may also have a trophic effect.
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In this study, we describe in detail the anatomy of nuclei involved in seasonal fertility regulation (SFR) in ewes. For this purpose, the intergeniculate leaflet of the visual thalamus, the caudal hypothalamic arcuate nucleus, and suprachiasmatic, paraventricular and supraoptic nuclei of the rostral hypothalamus were morphometrically and qualitatively analyzed in Nissl-stained serial sections, in the three anatomical planes. In addition, data were collected on calcium-binding proteins and cell phenotypes after immunostaining alternate serial sections for calretinin, parvalbumin and calbindin. For a complete neuroanatomical study, glial architecture was assessed by immunostaining and analyzing alternate sections for glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA1). The results showed a strong microglial and astroglia reaction around the hypothalamic nuclei of interest and around the whole 3rd ventricle of the ewe brain. Moreover, we correlated cytoarchitectonic coordinates of panoramic serial sections with their macroscopic localization and extension in midline sagittal-sectioned whole brain to provide guidelines for microdissecting nuclei involved in SFR.
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The explosive diversity of rainfrogs (Pristimantis spp) reaches its highest levels in the mountains of the Tropical Andes, with remarkable cryptic species mainly in unexplored areas of Ecuador. Based on phylogenetics, morphometric traits, skull osteology and bioacoustics, we describe two new species of Pristimantis, previously confused with Pristimantisgladiator, that belong to the subgenus Trachyphrynus traditionally known as the Pristimantismyersi species group. The two new taxa are closely related, but have allopatric distributions. We discuss the importance of the Quijos and Pastaza River valleys in the diversification along Amazonian slopes of the Ecuadorian Andes.
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BACKGROUND: The effect of disease-modifying therapies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine response is unclear. OBJECTIVES: We aim to determine the immunological responses to SARS-CoV-2 in multiple sclerosis (MS) and anti-CD20-treated patients with other autoimmune diseases (AID). METHODS: Humoral and cellular responses we determined before and 30-90 days after vaccination in patients with MS and anti-CD20-treated patients with other AID in two Catalan centers. RESULTS: 457 patients were enrolled. Findings showed that humoral response decreased under anti-CD20s or sphingosine 1-phosphate receptor modulators (S1PRM) and with longer treatment duration and increased after 4.5 months from the last anti-CD20 infusion. Cellular response decreased in S1PRM-treated. Patients on anti-CD20 can present cellular responses even in the absence of antibodies. CONCLUSION: Anti-CD20s and S1PRM modify the immunological responses to SARS-CoV-2 vaccines.
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COVID-19 , Esclerosis Múltiple , Anticuerpos Antivirales , COVID-19/prevención & control , Vacunas contra la COVID-19 , Humanos , Esclerosis Múltiple/tratamiento farmacológico , SARS-CoV-2 , VacunaciónRESUMEN
We describe a new species of Neotropical spiny-lizard of the genus Echinosaura from the Imbabura and Carchi Provinces on the western slopes of the Andes in northwestern Ecuador. The new species mostly resembles E. horrida. However, it can be distinguished from all congeners by having keeled enlarged dorsal scales forming a paired vertebral row, two paravertebral series of short oblique rows of projecting scales, and a pair of spine-like scales on temporal and nuchal regions. We also provide a detailed description of the osteology of the skull and pectoral girdle of the new species and present a phylogenetic hypothesis for Echinosaura based on three mitochondrial genes (12S, 16S, ND4) and one nuclear gene (c-mos).
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The protective effect of the efferent system against acoustic trauma (AT) has been shown by several experimental approaches, including damage to one ear, sectioning of the olivocochlear bundle (OCB) in the floor of the IV ventricle, and knock-in mice overexpressing outer hair cell (OHC) cholinergic receptors, among others. Such effects have been related to changes in the regulation of the cholinergic efferent system and in cochlear amplification, which ultimately reverse upon protective hearing suppression. In addition to well-known circuits of the brainstem, the descending corticofugal pathway also regulates efferent neurons of the olivary complex. In this study, we applied our recently developed experimental paradigm of multiple sessions of electrical stimulation (ES) to activate the efferent system in combination with noise overstimulation. ABR thresholds increased 1 and 2 days after AT (8-16 kHz bandpass noise at 107 dB for 90 min) recovering at AT + 14 days. However, after multiple sessions of epidural anodal stimulation, no changes in thresholds were observed following AT. Although an inflammatory response was also observed 1 day after AT in both groups, the counts of reactive macrophages in both experimental conditions suggest decreased inflammation in the epidural stimulation group. Quantitative immunocytochemistry for choline acetyltransferase (ChAT) showed a significant decrease in the size and optical density of the efferent terminals 1 day after AT and a rebound at 14 days, suggesting depletion of the terminals followed by a long-term compensatory response. Such a synthesis recovery was significantly higher upon cortical stimulation. No significant correlation was found between ChAT optical density and size of the buttons in sham controls (SC) and ES/AT + 1day animals; however, significant negative correlations were shown in all other experimental conditions. Therefore, our comparative analysis suggests that cochleotopic cholinergic neurotransmission is also better preserved after multisession epidural stimulation.
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We provide several lines of evidence to delimit a new species of Hyloscirtus and define its phylogenetic position inside the Hyloscirtus bogotensis group. The new species is the sister taxon to Hyloscirtus mashpi and is related to a clade formed by H. alytolylax and a putative new species from the province of El Oro in, southwestern Ecuador. Hyloscirtus conscientia sp. nov. is described from the montane forests of the Mira River basin in the extreme northwestern Ecuador. The new species is characterized as follows: tympanic annulus conspicuous, tip of snout in dorsal view subacuminate, middorsal stripe formed by melanophores larger and less dense, dorsal skin with individual iridophores forming dots, scarcely distributed across dorsum. Our study also highlights the importance of the Mira River Valley as a biogeographic barrier; suggesting research efforts north and south of the valley are likely to reveal additional endemic cryptic diversity. Finally, our partnership with Reserva: The Youth Land Trust, Rainforest Trust and EcoMinga Foundation has produced a novel and meaningful way to connect young people with biodiversity discovery and habitat conservation.
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Deafness affects the expression and distribution of voltage-dependent potassium channels (Kvs) of central auditory neurons in the short-term, i.e., hours to days, but the consequences in the expression of Kvs after long-term deafness remain unknown. We tested expression and distribution of Kv1.1 and Kv3.1b, key for auditory processing, in the rat cochlear nucleus (CN), and in the inferior colliculus (IC), at 1, 15 and 90 days after mechanical lesion of the cochlea, using a combination of qRT-PCR and Western blot in the whole CN, along with semi-quantitative immunocytochemistry in the AVCN, where the role of both Kvs in excitability control for accurate auditory timing signal processing is well established. Neither Kv1.1/Kv3.1b mRNA or protein expression changed significantly in the CN between 1 and 15 days after deafness. At 90 days post-lesion, however, mRNA and protein expression for both Kvs increased, suggesting that expression regulation of Kv1.1 and Kv3.1b is part of cellular mechanisms for long-term adaptation to auditory input deprivation in the CN. Consistent with these findings, immunocytochemical localization showed increased labeling intensity for both Kvs in the AVCN at day 90 after cochlear lesion, further supporting that up-regulation of Kv1.1 and Kv3.1b in neurons of this CN division, over a long term after auditory deprivation, may be required to adapt intrinsic excitability to altered input. Contrary to findings in the CN, in the IC, expression levels of Kv1.1 and Kv3.1b did not undergo major changes after cochlear lesion. In particular, there was no evidence of long-term up-regulation of neither Kv1.1 or Kv3.1b, supporting that such post-lesion adaptive mechanism may not be needed in the IC. This suggests that post-lesion plastic adaptations to auditory input deprivation are not stereotypical along the auditory pathway.
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Rat auditory cortex was subjected to 0.1 mA anodal direct current in seven 10-min sessions on alternate days. Based on the well-known auditory cortex control of olivocochlear regulation through corticofugal projections, auditory brainstem responses (ABRs) were recorded as an indirect test of the effectiveness and reversibility of the multisession protocol of epidural stimulation. Increases of 20-30 dB ABR auditory thresholds shown after epidural stimulation reverted back to control levels 10 min after a single session. However, increases in thresholds revert 4 days after multisession stimulation. Less changes in wave amplitudes and threshold shifts were shown in ABR recorded contralaterally to the electrically stimulated side of the brain. To assess tissue effects of epidural electric stimulation on the brain cortex, well characterized functional anatomical markers of glial cells (GFAP/astrocytes and Iba1/microglial cells) and neurons (c-Fos) were analyzed in alternate serial sections by quantitative immunocytochemistry. Restricted astroglial and microglial reactivity was observed within the cytoarchitectural limits of the auditory cortex. However, interstitial GFAP overstaining was also observed in the ventricular surface and around blood vessels, thus supporting a potential global electrolytic stimulation of the brain. These results correlate with extensive changes in the distribution of c-Fos immunoreactive neurons among layers along sensory cortices after multisession stimulation. Quantitative immunocytochemical analysis supported this idea by showing a significant increase in the number of positive neurons in supragranular layers and a decrease in layer 6 with no quantitative changes detected in layer 5. Our data indicate that epidural stimulation of the auditory cortex induces a reversible decrease in hearing sensitivity due to local, restricted epidural stimulation. A global plastic response of the sensory cortices, also reported here, may be related to electrolytic effects of electric currents.
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The rat auditory cortex (AC) is becoming popular among auditory neuroscience investigators who are interested in experience-dependence plasticity, auditory perceptual processes, and cortical control of sound processing in the subcortical auditory nuclei. To address new challenges, a procedure to accurately locate and surgically expose the auditory cortex would expedite this research effort. Stereotactic neurosurgery is routinely used in pre-clinical research in animal models to engraft a needle or electrode at a pre-defined location within the auditory cortex. In the following protocol, we use stereotactic methods in a novel way. We identify four coordinate points over the surface of the temporal bone of the rat to define a window that, once opened, accurately exposes both the primary (A1) and secondary (Dorsal and Ventral) cortices of the AC. Using this method, we then perform a surgical ablation of the AC. After such a manipulation is performed, it is necessary to assess the localization, size, and extension of the lesions made in the cortex. Thus, we also describe a method to easily locate the AC ablation postmortem using a coordinate map constructed by transferring the cytoarchitectural limits of the AC to the surface of the brain.The combination of the stereotactically-guided location and ablation of the AC with the localization of the injured area in a coordinate map postmortem facilitates the validation of information obtained from the animal, and leads to a better analysis and comprehension of the data.
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Corteza Auditiva/diagnóstico por imagen , Encéfalo/patología , Técnicas Estereotáxicas/estadística & datos numéricos , Estimulación Acústica , Animales , Modelos Animales de Enfermedad , RatasRESUMEN
The auditory cortex (AC) dynamically regulates responses of the Organ of Corti to sound through descending connections to both the medial (MOC) and lateral (LOC) olivocochlear efferent systems. We have recently provided evidence that AC has a reinforcement role in the responses to sound of the auditory brainstem nuclei. In a molecular level, we have shown that descending inputs from AC are needed to regulate the expression of molecules involved in outer hair cell (OHC) electromotility control, such as prestin and the α10 nicotinic acetylcholine receptor (nAchR). In this report, we show that descending connections from AC to olivocochlear neurons are necessary to regulate the expression of molecules involved in cochlear afferent signaling. RT-qPCR was performed in rats at 1, 7 and 15 days after unilateral ablation of the AC, and analyzed the time course changes in gene transcripts involved in neurotransmission at the first auditory synapse. This included the glutamate metabolism enzyme glutamate decarboxylase 1 (glud1) and AMPA glutamate receptor subunits GluA2-4. In addition, gene transcripts involved in efferent regulation of type I spiral ganglion neuron (SGN) excitability mediated by LOC, such as the α7 nAchR, the D2 dopamine receptor, and the α1, and γ2 GABAA receptor subunits, were also investigated. Unilateral AC ablation induced up-regulation of GluA3 receptor subunit transcripts, whereas both GluA2 and GluA4 mRNA receptors were down-regulated already at 1 day after the ablation. Unilateral removal of the AC also resulted in up-regulation of the transcripts for α7 nAchR subunit, D2 dopamine receptor, and α1 GABAA receptor subunit at 1 day after the ablation. Fifteen days after the injury, AC ablations induced an up-regulation of glud1 transcripts.
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Corteza Auditiva/fisiología , Cóclea/fisiología , Animales , Corteza Auditiva/anatomía & histología , Corteza Auditiva/lesiones , Vías Auditivas/fisiología , Glutamato Descarboxilasa/genética , Masculino , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Receptores AMPA/genética , Receptores de Dopamina D2/genética , Receptores de GABA-A/genética , Transmisión Sináptica/genética , Transmisión Sináptica/fisiología , Regulación hacia Arriba , Receptor Nicotínico de Acetilcolina alfa 7/genéticaRESUMEN
STUDY OBJECTIVES: Low flow supplemental oxygen is commonly prescribed to patients with obesity hypoventilation syndrome (OHS). However, there is a paucity of data regarding its efficacy and safety. The objective of this study was to assess the medium-term treatment efficacy of adding supplemental oxygen therapy to commonly prescribed treatment modalities in OHS. METHODS: In this post hoc analysis of a previous randomized controlled trial, we studied 302 sequentially screened OHS patients who were randomly assigned to noninvasive ventilation, continuous positive airway pressure, or lifestyle modification. Outcomes at 2 mo included arterial blood gases, symptoms, quality of life, blood pressure, polysomnography, spirometry, 6-min walk distance, and hospital resource utilization. Statistical analysis comparing patients with and without oxygen therapy in the three treatment groups was performed using an intention-to-treat analysis. RESULTS: In the noninvasive ventilation group, supplemental oxygen reduced systolic blood pressure although this could be also explained by a reduction in body weight experienced in this group. In the continuous positive airway pressure group, supplemental oxygen increased the frequency of morning confusion. In the lifestyle modification group, supplemental oxygen increased compensatory metabolic alkalosis and decreased the apnea-hypopnea index during sleep. Oxygen therapy was not associated with an increase in hospital resource utilization in any of the groups. CONCLUSIONS: After 2 mo of follow-up, chronic oxygen therapy produced marginal changes that were insufficient to consider it, globally, as beneficial or deleterious. Because supplemental oxygen therapy did not increase hospital resource utilization, we recommend prescribing oxygen therapy to patients with OHS who meet criteria with close monitoring. Long-term studies examining outcomes such as incident cardiovascular morbidity and mortality are necessary. CLINICAL TRIALS REGISTRATION: Clinicaltrial.gov, ID: NCT01405976.
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Síndrome de Hipoventilación por Obesidad/terapia , Terapia por Inhalación de Oxígeno/métodos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Análisis de los Gases de la Sangre/estadística & datos numéricos , Presión Sanguínea , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Polisomnografía/estadística & datos numéricos , Calidad de Vida , España , Espirometría/estadística & datos numéricos , Resultado del Tratamiento , Caminata/estadística & datos numéricos , Adulto JovenRESUMEN
BACKGROUND: Obesity hypoventilation syndrome (OHS) is associated with a high burden of cardiovascular morbidity (CVM) and mortality. The majority of patients with OHS have concomitant OSA, but there is a paucity of data on the association between CVM and OSA severity in patients with OHS. The objective of our study was to assess the association between CVM and OSA severity in a large cohort of patients with OHS. METHODS: In a cross-sectional analysis, we examined the association between OSA severity based on tertiles of oxygen desaturation index (ODI) and CVM in 302 patients with OHS. Logistic regression models were constructed to quantify the independent association between OSA severity and prevalent CVM after adjusting for various important confounders. RESULTS: The prevalence of CVM decreased significantly with increasing severity of OSA based on ODI as a continuous variable or ODI tertiles. This inverse relationship between OSA severity and prevalence of CVM was seen in the highest ODI tertile and it persisted despite adjustment for multiple confounders. Chronic heart failure had the strongest negative association with the highest ODI tertile. No significant CVM risk change was observed between the first and second ODI tertiles. Patients in the highest ODI tertile were younger, predominantly male, more obese, more hypersomnolent, had worse nocturnal and daytime gas exchange, lower prevalence of hypertension, better exercise tolerance, and fewer days hospitalized than patients in the lowest ODI tertile. CONCLUSIONS: In patients with OHS, the highest OSA severity phenotype was associated with reduced risk of CVM. This finding should guide the design of future clinical trials assessing the impact of interventions aimed at decreasing cardiovascular morbidity and mortality in patients with OHS. TRIAL REGISTRY: Clinicaltrial.gov; No.: NCT01405976; URL: www.clinicaltrials.gov.
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Enfermedades Cardiovasculares , Síndrome de Hipoventilación por Obesidad , Anciano , Análisis de los Gases de la Sangre/métodos , Enfermedades Cardiovasculares/etiología , Enfermedades Cardiovasculares/mortalidad , Estudios Transversales , Femenino , Humanos , Hipoxia/diagnóstico , Hipoxia/etiología , Masculino , Persona de Mediana Edad , Síndrome de Hipoventilación por Obesidad/sangre , Síndrome de Hipoventilación por Obesidad/complicaciones , Síndrome de Hipoventilación por Obesidad/diagnóstico , Síndrome de Hipoventilación por Obesidad/epidemiología , Polisomnografía/métodos , Prevalencia , Factores Protectores , Índice de Severidad de la Enfermedad , EspañaRESUMEN
In this review we analyse cochlear implantation in terms of the fundamental aspects of the functioning of the auditory system. Concepts concerning neuronal plasticity applied to electrical stimulation in perinatal and adult deep hypoacusis are reviewed, and the latest scientific bases that justify early implantation following screening for congenital deafness are discussed. Finally, this review aims to serve as an example of the importance of fostering the sub-specialty of neurotology in our milieu, with the aim of bridging some of the gaps between specialties and thus improving both the knowledge in the field of research on auditory pathologies and in the screening of patients. The objectives of this review, targeted above all towards specialists in the field of otorhinolaryngology, are to analyse some significant neurological foundations in order to reach a better understanding of the clinical events that condition the indications and the rehabilitation of patients with cochlear implants, as well as to use this means to foster the growth of the sub-specialty of neurotology.
TITLE: Neurotologia e implantacion coclear.En esta revision se analiza la implantacion coclear en relacion con los fundamentos del funcionamiento del sistema auditivo. Se revisan los conceptos sobre plasticidad neuronal aplicados a la estimulacion electrica en la hipoacusia profunda perinatal y del adulto, y se comentan las bases cientificas actuales que justifican la implantacion precoz tras el cribado de la sordera congenita. Finalmente, se propone esta revision como un ejemplo de la importancia de fomentar la subespecialidad de neurotologia en nuestro medio, a fin de tender puentes entre especialidades que mejoren tanto el conocimiento en el campo de la investigacion de la patologia auditiva como en el cuidado de los pacientes. Los objetivos de esta revision, dirigida sobre todo a especialistas del campo de la otorrinolaringologia, son los de analizar algunos fundamentos neurologicos de relevancia para comprender mejor los eventos clinicos que condicionan las indicaciones y la rehabilitacion de los pacientes con implantes cocleares, asi como estimular por este medio la potenciacion de la subespecialidad en neurotologia.
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Implantación Coclear , Pérdida Auditiva/cirugía , Otoneurología , Estimulación Acústica , Adaptación Fisiológica , Factores de Edad , Corteza Auditiva/fisiopatología , Vías Auditivas/fisiopatología , Implantación Coclear/métodos , Implantes Cocleares , Diagnóstico Precoz , Intervención Médica Temprana , Potenciales Evocados Auditivos , Neuronas GABAérgicas/fisiología , Pérdida Auditiva/epidemiología , Pérdida Auditiva/fisiopatología , Humanos , Lenguaje , Música , Red Nerviosa/fisiopatología , Plasticidad Neuronal , Neuronas/clasificación , Neuronas/fisiología , Otoneurología/organización & administración , Otoneurología/tendencias , Discriminación de la Altura Tonal/fisiología , Sociedades MédicasRESUMEN
Electromotile activity in auditory outer hair cells (OHCs) is essential for sound amplification. It relies on the highly specialized membrane motor protein prestin, and its interactions with the cytoskeleton. It is believed that the expression of prestin and related molecules involved in OHC electromotility may be dynamically regulated by signals from the acoustic environment. However little is known about the nature of such signals and how they affect the expression of molecules involved in electromotility in OHCs. We show evidence that prestin oligomerization is regulated, both at short and relatively long term, by acoustic input and descending efferent activity originating in the cortex, likely acting in concert. Unilateral removal of the middle ear ossicular chain reduces levels of trimeric prestin, particularly in the cochlea from the side of the lesion, whereas monomeric and dimeric forms are maintained or even increased in particular in the contralateral side, as shown in Western blots. Unilateral removal of the auditory cortex (AC), which likely causes an imbalance in descending efferent activity on the cochlea, also reduces levels of trimeric and tetrameric forms of prestin in the side ipsilateral to the lesion, whereas in the contralateral side prestin remains unaffected, or even increased in the case of trimeric and tetrameric forms. As far as efferent inputs are concerned, unilateral ablation of the AC up-regulates the expression of α10 nicotinic Ach receptor (nAChR) transcripts in the cochlea, as shown by RT-Quantitative real-time PCR (qPCR). This suggests that homeostatic synaptic scaling mechanisms may be involved in dynamically regulating OHC electromotility by medial olivocochlear efferents. Limited, unbalanced efferent activity after unilateral AC removal, also affects prestin and ß-actin mRNA levels. These findings support that the concerted action of acoustic and efferent inputs to the cochlea is needed to regulate the expression of major molecules involved in OHC electromotility, both at the transcriptional and posttranscriptional levels.
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INTRODUCTION: This study aimed to assess the top-down control of sound processing in the auditory brainstem of rats. Short latency evoked responses were analyzed after unilateral or bilateral ablation of auditory cortex. This experimental paradigm was also used towards analyzing the long-term evolution of post-lesion plasticity in the auditory system and its ability to self-repair. METHOD: Auditory cortex lesions were performed in rats by stereotactically guided fine-needle aspiration of the cerebrocortical surface. Auditory Brainstem Responses (ABR) were recorded at post-surgery day (PSD) 1, 7, 15 and 30. Recordings were performed under closed-field conditions, using click trains at different sound intensity levels, followed by statistical analysis of threshold values and ABR amplitude and latency variables. Subsequently, brains were sectioned and immunostained for GAD and parvalbumin to assess the location and extent of lesions accurately. RESULTS: Alterations in ABR variables depended on the type of lesion and post-surgery time of ABR recordings. Accordingly, bilateral ablations caused a statistically significant increase in thresholds at PSD1 and 7 and a decrease in waves amplitudes at PSD1 that recover at PSD7. No effects on latency were noted at PSD1 and 7, whilst recordings at PSD15 and 30 showed statistically significant decreases in latency. Conversely, unilateral ablations had no effect on auditory thresholds or latencies, while wave amplitudes only decreased at PSD1 strictly in the ipsilateral ear. CONCLUSION: Post-lesion plasticity in the auditory system acts in two time periods: short-term period of decreased sound sensitivity (until PSD7), most likely resulting from axonal degeneration; and a long-term period (up to PSD7), with changes in latency responses and recovery of thresholds and amplitudes values. The cerebral cortex may have a net positive gain on the auditory pathway response to sound.
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Corteza Auditiva/fisiología , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Animales , Corteza Auditiva/fisiopatología , Masculino , Ratas , Ratas WistarRESUMEN
The cortico-collicular pathway is a bilateral excitatory projection from the cortex to the inferior colliculus (IC). It is asymmetric and predominantly ipsilateral. Using microarrays and RT-qPCR we analyzed changes in gene expression in the IC after unilateral lesions of the auditory cortex, comparing the ICs ipsi- and contralateral to the lesioned side. At 15 days after surgery there were mainly changes in gene expression in the IC ipsilateral to the lesion. Regulation primarily involved inflammatory cascade genes, suggesting a direct effect of degeneration rather than a neuronal plastic reorganization. Ninety days after the cortical lesion the ipsilateral IC showed a significant up-regulation of genes involved in apoptosis and axonal regeneration combined with a down-regulation of genes involved in neurotransmission, synaptic growth, and gap junction assembly. In contrast, the contralateral IC at 90 days post-lesion showed an up-regulation in genes primarily related to neurotransmission, cell proliferation, and synaptic growth. There was also a down-regulation in autophagy and neuroprotection genes. These findings suggest that the reorganization in the IC after descending pathway deafferentation is a long-term process involving extensive changes in gene expression regulation. Regulated genes are involved in many different neuronal functions, and the number and gene rearrangement profile seems to depend on the density of loss of the auditory cortical inputs.