Thesis advisor: Michael A. McDannald / Thesis advisor: John P. Christianson / The ability to accurately evaluate and respond to threats is vital to survival. Disruptions in neural circuits of fear give rise to maladaptive threat responding, and have clinical implications in fear and anxiety disorders. To better inform therapeutic interventions, it is imperative that roles for regions classically associated with fear continue to be refined, and that novel nodes are incorporated into what is most certainly a larger fear circuit. In the canonical view, threat estimates are generated at the level of the amygdala and sent to the ventrolateral periaqueductal gray (vlPAG), which organizes an appropriate behavioral response, most notably freezing. Despite a multitude of studies successfully linking the vlPAG and Pavlovian fear behavior, evidence of a direct neural correlate for fear expression in the vlPAG is lacking. By contrast, a role for the caudal substantia nigra (cSN) in fear, stands apart from its canonical associations with movement and reward processes. Although there is new interest in examining a role for the nigra in fear modulation, this is essentially an uncharted area of discovery. The goals of this dissertation are three-fold. First, to propose a role for vlPAG activity in threat estimation, a function previously restricted to the upstream amygdala. Second, to scrutinize vlPAG neural activity using a novel multi-cue Pavlovian procedure and identify the long-anticipated, direct neural correlate for fear expression. Third, to present causal evidence supporting the cSN as a potential node in a circuit that most certainly extends beyond regions canonically associated with fear. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

Made available in DSpace on 2018-08-01T22:57:56Z (GMT). No. of bitstreams: 1 tese_7274_021 - DISSERTAÇÃO JOHNATHAN JUNIOR VAZ CARVALHO.pdf: 702170 bytes, checksum: d050a58ac0d19c54163d1007bd3edd12 (MD5) Previous issue date: 2016-07-19 / A substância cinzenta periaquedutal dorsal (SCPD) é uma estrutura mesencefálica envolvida na mediação de comportamentos defensivos associados aos transtornos de ansiedade generalizada (TAG) e de pânico (TP). Existem evidências que indicam um envolvimento da neurotransmissão noradrenérgica da SCPD na modulação da ansiedade, no entanto, não existe evidência sobre sua participação nos ataques de pânico. Neste sentido, o objetivo do presente estudo foi investigar a participação da neurotransmissão noradrenérgica da SCPD na mediação de comportamentos defensivos relacionados ao TAG e ao TP em animais testados no labirinto em T elevado (LTE), um modelo animal que associa a resposta de esquiva inibitória ao TAG e a resposta de fuga ao TP. Para tal, ratos Wistar receberam a administração intra-SCPD de noradrenalina (10, 30 ou 60 nmoles/0,1μL) ou salina e foram testados no LTE. Adicionalmente, investigamos o efeito do pré-tratamento intra-SCPD com os antagonistas não seletivos de receptores alfa e beta-adrenérgicos, fentolamina e propranolol, respectivamente, no efeito da injeção de noradrenalina na mesma estrutura. Nossos resultados mostram que a administração intra-SCPD de noradrenalina na maior dose prejudicou a aquisição da esquiva inibitória, sugerindo um efeito do tipo ansiolítico, porém não apresentou efeito sobre a resposta de fuga no LTE. Além disso, a injeção de noradrenalina não alterou a atividade locomotora dos animais no teste do campo aberto, sugerindo que o efeito ansiolítico não foi devido a um aumento na atividade exploratória. Os resultados mostram ainda que o pré-tratamento intra-SCPD de fentolamina ou propranolol atenuou o efeito do tipo ansiolítico da noradrenalina. Assim, o presente estudo sugere um envolvimento da neurotransmissão noradrenérgica na SCPD, via receptores alfa e beta-adrenérgicos, em reações defensivas associadas com o TAG, mas não com o TP em animais submetidos ao LTE.

Damage precipitating cognitive decline in Alzheimer's disease (AD) begins long before behavioural alterations become clinically apparent. At this prodromal stage, communication between networks of neurons connecting different brain regions starts to break down; setting in motion a chain of events leading to clinical AD. A significant challenge facing Alzheimer's researchers today is finding a cheap, easy-to-perform test capable of detecting prodromal AD. Such a test would afford significant benefits to patients, including a chance of early intervention. Perhaps, more importantly, it would also aid development and testing of novel therapies aimed at combating AD before it causes irreversible damage. Since oscillations in electrical field activity are important for facilitating connectivity across the brain and have been seen to alter in AD, this work studied how oscillations and regional connectivity are affected in the AD brain. Specifically, local field oscillations were recorded from the hippocampus and prelimbic cortex (regions implicated in memory formation and maintenance) in a double transgenic AD model - the TASTPM mouse. Here, periods of predominant theta activity were assessed both spontaneously, under urethane anaesthesia and following electrical induction through dorsal periaqueductal gray (dPAG) stimulation. From these recordings, spectral power and connectivity between regions was assessed using both a traditional measure of functional connectivity (inter-region correlation) and through a novel information theoretic approach measuring effective connectivity (transfer entropy).Perhaps the most prominent finding from this study was the observation that young TASTPM mice, at an age prior to overt cognitive decline or plaque deposition, showed significant alterations in measures of both functional and effective connectivity. This suggests that such measures may be used as biomarkers predictive of prodromal AD and, as such, may be used to aid development of drugs targeted towards treatment of prodromal AD.This study also uncovered a number of interesting observations concerning hippocampal/prelimbic connectivity. Firstly, although spectral power and inter-regional correlation peaked at ∼ 3Hz, information flow between these structures was strongest at ∼6Hz. This suggests that low and high-band theta activity may fulfil separate functions. Secondly, at theta frequencies, information flowed predominantly from the prelimbic cortex to the hippocampus. However, during lower frequency activity, information flowed predominantly in the opposite direction. Suggesting that separate frequency bands may be important for routing information flow between these structures. Finally, the strength of information transfer was seen to oscillate at approximately double the frequency of its carrier signal, perhaps suggesting locking of information transfer to certain phases of an underlying oscillation. Therefore, oscillations may structure information transfer by temporal windowing and frequency-locked routing; processes which can be studied using measures of effective connectivity such as transfer entropy.

Each year, over 50 million Americans suffer from persistent pain, including debilitating headaches, joint pain, and severe back pain. Although morphine is amongst the most effective analgesics available for the management of severe pain, prolonged morphine treatment results in decreased analgesic efficacy (i.e., tolerance). Despite significant headway in the field, the mechanisms underlying the development of morphine tolerance are not well understood. The midbrain ventrolateral periaqueductal gray (vlPAG) is a primary neural substrate for the analgesic effects of morphine, as well as for the development of morphine tolerance. A growing body of literature indicates that activated glia (i.e., microglia and astrocytes) facilitate pain transmission and oppose morphine analgesia, making these cells important potential targets in the treatment of chronic pain. Morphine affects glia by binding to the innate immune receptor toll-like receptor 4 (TLR4), leading to the release of proinflammatory cytokines and opposition of morphine analgesia. Despite the established role of the vlPAG as an integral locus for the development of morphine tolerance, to date, no studies have examined the role of glia activation within this region. Additionally, the role of TLR4 in the development of tolerance has not been elucidated. This dissertation seeks to address the lack of knowledge regarding the role of vlPAG glia and TLR4 in the development of morphine tolerance by (1) Characterizing the effects of chronic morphine and peripheral inflammatory pain on vlPAG glial cell activity; (2) Investigating the role of glia activation within the vlPAG in the development of morphine tolerance; (3) Characterizing the role of the glial receptor TLR4 within the vlPAG in the development of morphine tolerance; and (4) Characterizing the glia to neuron signaling mechanisms involved in the development of morphine tolerance. These experiments, together, provide novel information about the mechanism by which central nervous system glia regulate morphine tolerance, and identify a potential therapeutic target for the enhancement of analgesic efficacy in the clinical treatment of chronic pain.

Antibody-coated microprobes were used to determine whether immunoreactive enkephalins were released in response to fatiguing isometric contractions of the hind-limb muscles in cats anesthetized with α-chloralose. Contractions were performed by stimulating the tibial nerve via a microprocessor-controlled stimulator. Microprobes were inserted into the periaqueductal grey (P 0.5-1.0 mm) prior to, during and following fatiguing contractions. During fatiguing contractions, mean arterial blood pressure increased by 76 ± 9 mmHg above resting and recovery levels. Levels of immunoreactive enkephalins were elevated in the dorsolateral periaqueductal grey during the isometric contraction when compared to resting levels. It is possible that isometric muscle contraction causes the release of Met-enkephalin-like substances in the periaqueductal grey.

Plants of the genus Kielmeyera, family Clusiaceae are used by the population of the Northeast of the Brazil in traditional medicine to treat various diseases, such as pain and inflammation diseases. A recent study demonstrated antitumor activity for K. rugosa, however, other pharmacological activities have never been studied, for example antihyperalgesic and anti inflammatory activities. Thus, the aim of this study was to evaluate the antihyperalgesic and anti - inflammatory effects of the methanol extract from the stems of K. rugosa (MEKR) in rodents. Swiss mice (25-35 g ) were divided into groups and subjected to treatment with MEKR (., 100, 200 and 400 mg/kg, oral administration, p.o.) , vehicle (0.9% saline solution + 0.2% Tween 80) or standard drug (i.p.). The hypernociception was evaluated at times 0.5 , 1, 2 , and 3 hours after administration (i.pl.) of carrageenan (CG; 300 mg/paw), tumor necrosis factor-α (TNF-α, 100 pg/paw), Prostaglandin E2 (PGE2; 100ƞg/pata) or dopamine (DA, 30 μg/paw) using the digital analgesymeter (von Frey). In the evaluation of anti-inflammatory activity two protocols were used, the first induced by GC (300 mg/well) at 4 hours after pleurisy which the full and differential counts were made of leukocytes as well as the dosage levels of TNF-α and IL-1β pleural lavage. In another protocol conducted to investigate the anti-inflammatory activity corresponded to paw edema induced by GC (1 %/40μL), the paw volume was measured with the aid of plethysmometer at 0-6h after CG. The cytotoxicity of MEKR was evaluated by the MTT colorimetric method. To determine the possible involvement of areas of the Central Nervous System (CNS), the animals were treated and ninety minutes, were anesthetized, perfused, the brains extracted and cut into the cryostat. The brain sections were subjected to immunofluorescence protocol for Fos protein. The motor coordination of the animal was assessed by the Rota Rod test (7 rpm, 180 s). The experimental protocols were approved by the ethics committee of the UFS (CEPA/UFS: 102/11) The results were expressed as mean ± standard error of the mean. Differences between groups were analyzed using the ANOVA one way followed by Tukey s test. The acute pretreatment with MEKR significantly inhibited hyperalgesia induced by nociceptive agents, CG, TNF-α, PGE2 and DA (p < 0.001). The MEKR inhibited the leukocyte recruitment into the pleural cavity (p < 0.01). This was due to the inhibition of leukocyte migration inhibition of neutrophils. The levels of cytokines, TNF-α (p < 0.01) and IL-1β (p < 0.001) were also reduced when the animals were treated with MEKR. MEKR decreased edema formation induced by CG (p < 0.001). However, MEKR showed no cytotoxic effect or change in motor coordination animals. In the Fos protein immunofluorescence test, MEKR showed that the olfactory bulb (p < 0.01), piriform cortex (p < 0.01) and periaqueductal gray (p < 0.001) for the active significantly of the CNS. Therefore, we conclude that MEKR has antihyperalgesic activity probably by activating the central nervous system areas associated with pain modulation and by reduction the production of proinflammatory cytokines, without traces of cytotoxicity. / Diversas plantas do gênero Kielmeyera, família Clusiaceae são utilizadas pela população do Nordeste brasileiro na medicina tradicional para o tratamento de diversas doenças, incluindo distúrbios dolorosos e inflamatórios. Um estudo recente demonstrou atividade antitumoral para a K. rugosa, no entanto, outras atividades farmacológicas nunca foram estudadas para esta espécie vegetal, por exemplo seu possível perfil analgésico e anti-inflamatório. Dessa forma, o objetivo do trabalho foi avaliar o efeito antihiperalgésico e anti-inflamatório do extrato metanólico obtido do caule de K. rugosa (EMKR) em roedores. Foram utilizados camundongos Swiss machos (25-35 g), divididos em grupos e submetidos ao tratamento agudo com EMKR (100, 200 e 400 mg/kg; por via oral, v.o.), veículo (solução salina 0,9% + tween 80 0,2%; v.o.) ou droga padrão (i.p.). A hipernocicepção foi avaliada nos tempos 0,5, 1, 2 e 3 h após a administração (i.pl.) de carragenina (CG; 300 μg/pata), Fator de necrose tumoral-α (TNF-α; 100 pg/pata), Prostaglandina E2 (PGE2; 100ƞg/pata) ou Dopamina (DA; 30 μg/pata), e foram avaliados utilizando-se o analgesímetro digital (Von Frey). Na avaliação da atividade anti-inflamatória foram utilizados dois protocolos, o primeiro de pleurisia induzida por CG (300 μg/cavidade), no qual após 4 horas foram realizadas as contagens total e diferencial de leucócitos, bem como as dosagens dos níveis de TNF-α e IL-1β do lavado pleural. Em outro protocolo realizado para investigar à atividade anti-inflamatória correspondeu ao edema de pata induzida por CG (1%/40μL); o volume da pata foi medido com auxílio do pletismomêtro nos tempos 0-6h após a CG. A citotoxicidade do MEKR foi avaliada através do método colorimétrico do MTT. Para determinar o possível envolvimento de áreas do Sistema Nervoso Central (SNC), os animais foram tratados e, noventa minutos após, foram anestesiados, perfundidos, os cérebros extraídos e cortados em criostato. As secções cerebrais foram submetidas ao protocolo de imunofluorescência para proteína Fos. A coordenação motora do animal foi avaliada através do teste do Rota Rod (7 rpm, 180 s). Os protocolos experimentais foram aprovados pelo comitê de ética da UFS (CEPA/UFS: 102/11) Os resultados foram expressos como média ± erro padrão da média. As diferenças entre os grupos foram analisadas por meio do teste de variância ANOVA, uma via, seguido pelo teste de Tukey. O pré-tratamento com EMKR inibiu significativamente a hiperalgesia induzida pelos agentes álgicos, CG, TNF-α, PGE2 e DA (p < 0,001). O EMKR também foi capaz de inibir o recrutamento leucocitário para a cavidade pleural (p < 0,01). Esta inibição leucocitária ocorreu devido à inibição na migração dos neutrófilos. Os níveis das citocinas, TNF-α (p < 0,01) e IL-1β (p < 0,001) também foram reduzidos quando os animais foram tratados com EMKR. Quanto ao edema, o EMKR diminuiu a formação induzida pela CG (p < 0,001). No entanto, o MEKR não apresentou efeito citotóxico ou alteração da coordenação motora dos animais. No teste de imunofluorescência para proteína Fos, o tratamento com MEKR ativou significativamente o bulbo olfatório (p < 0,01), córtex piriforme (p < 0,01) e a substância cinzenta periaquedutal (p < 0,001), áreas do SNC. Os resultados sugerem que o MEKR possui atividade antihiperalgésica e anti-inflamatória provavelmente por ativação de áreas do sistema nervoso central relacionadas com a modulação da dor e por reduzir a produção de citocinas pró-inflamatórias, sem traços de citotoxicidade.

A circuitaria neuro-anatômica envolvida com a organização de respostas de medo inclui muitos sítios subcorticais diferentes, dois dos quais são a região dorsal da matéria cinzenta periaquedutal (dPAG) e as camadas intermediárias e profundas do colículo superior (i/dlSC). Este estudo investigou como as células destas duas regiões mudam de atividade em um rato que foi colocado diante de seu predador, o gato, comparado com outras situações onde o risco menor. 11 ratos wistar machos passaram por cirurgia para implantação de um microdriver contendo 8 tetrodos, que detectou 39 células na dPAG de 7 ratos e 44 células nas i/dlSC de 4 ratos. A atividade das células foi registrada em uma condição de base e em quatro condições experimentais distintas: o rato confinado, o rato diante de uma novidade, diante de um predador e diante do contexto predatório. Os dados coletados foram analisados por scripts de MATLAB e cada célula foi classificada para sua responsividade às condições experimentais, à mudança do comportamento do rato, à velocidade e à posição do rato no aparato. Na dPAG as células se mostraram mais responsivas a condição do gato do que as demais condições experimentais, tanto em número de células como em aumento de atividade celular. Uma quantidade menor de células mostrou-se responsiva a mudanças de comportamento, particularmente os comportamentos de defesa. Nas i/dlSC as células também se mostraram mais responsivas para o gato, seguido do contexto, em ambos os casos com diminuição de atividade celular, que foi mais intensa no gato. Uma quantidade menor de células pareceu responder de forma similar para as diferentes mudanças comportamentais. Interpretamos esses dados propondo que a dPAG possui uma função sinalizadora de medo, fortemente ativada durante o gato, e que as i/dlSC são inibidas diante do gato a fim de evitar a captação de estímulos irrelevantes para lidar com a situação de risco. / The neuroanatomical circuitry involved with the organization of fear responses includes a great number of subcortical sites, two of which are the dorsal periaqueductal gray (dPAG) and the intermediate and deep layers of the superior colliculus (i/dlSC). This study investigated how the cellular activity in these regions changed in a rat that was exposed to one of its predators, a cat, when compared with lower risk situations. 11 male wistar rats underwent surgery to implant a microdriver containing 8 tetrodes, which detected 39 cells in the dPAG of 7 rats and 44 cells in the i/dlSC of 4 rats. Cell activity was registered in a basal condition and then again in for experimental conditions: the rat confined in a smaller space, the rat facing a novel stimulus, the rat facing a cat and the rat facing the predatory context. Collected data was analyzed using MATLAB and each cell was classified according to its responsivity to the experimental conditions, to the rats switches in behavior, to the rats speed and position in the experimental apparatus. In the dPAG, cells were shown to be more responsive to the cat condition over the other conditions, both in terms of number of responsive cells and intensity of increase in firing activity. A smaller number of cells were responsive to behavior switching, being especially sensitive to the initiation of defensive behaviors. In the i/dlSC, cells were more responsive to the cat, followed by the predatory context, in both cases with a general reduction of cellular activity that was more intensive for the cat. A smaller number of cells was responsive in similar ways for behavior switching across experimental conditions. We interpret this data by proposing that the dPAG acts signaling a state of fear, particularly during a high risk situation, and the i/dlSC are inhibited during riskier situations so as to block irrelevant environmental stimuli.

O tratamento com morfina ao final da prenhez, faz com que uma única dose dessa droga durante a lactação iniba o comportamento maternal e estimule a caça predatória. A intensidade dessa mudança comportamental depende da dose desafio de morfina utilizada. A exposição a drogas de abuso pode levar a um fenômeno denominado tolerância reversa, que consiste na exacerbação dos efeitos do tratamento agudo com um fármaco observada após a interrupção de um tratamento crônico. O objetivo deste estudo foi avaliar como os efeitos do pré-tratamento com morfina durante a gestação podem influenciar na seleção comportamental após o parto. Ratas foram expostas simultaneamente a filhotes e insetos, sendo observada a expressão dos comportamentos maternal e predatório. As ratas foram tratadas com injeções diárias de morfina (3,5 mg/Kg, s.c.) do 17º ao 21º dia de gestação, e desafiadas agudamente no 5o ou 6o dia de lactação com doses distintas de morfina (0,5, 1,0 e 1,5mg/Kg; grupos MM0,5, MM1,0 e MM1,5) ou salina (grupo MS). Grupos controle foram pré-tratados com salina e desafiados com morfina (0,5, 1,0 e 1,5mg/Kg; grupos SM0,5, SM1,0 e SM1,5) ou salina (grupo SS), respectivamente. Em seguida foram testadas no paradigma de escolha entre cuidar dos filhotes e caçar. Animais pré-tratados com morfina e desafiados com 1,0 mg/Kg tiveram parâmetros de comportamento maternal prejudicados e facilitação ao comportamento de caça de maneira significante, o que não foi observado nos animais desafiados com a dose de 0,5 mg/Kg. Animais desafiados com 1,5 mg/Kg de morfina tiveram prejuízo em relação ao comportamento maternal e facilitação do comportamento predatório tanto no grupo de fêmeas pré-tratadas com morfina, quanto com salina. Em ratas lactantes a exposição simultânea a filhotes e insetos permitiu revelar a existência de tolerância reversa à mudança comportamental induzida por estímulo opioidérgico. / Treatment of postpartum female rats with morphine inhibits maternal behavior. The same treatment also stimulates foraging in adult animals. Exposure to drugs of abuse may result in a progressive and enduring enhancement of their reinforcing effects. Puerperal treatment with morphine leads to reverse tolerance to this drug, ultimately influencing the effects of opiates on maternal behavior. The aim of the present study was to investigate whether abrupt withdrawal from repeated morphine treatment during late pregnancy may influence the effects of morphine on behavioral selection in lactating rats. Animals were exposed simultaneously to pups and insects, and the choice between taking care of the pups and hunting for insects was observed. Female Wistar rats were treated with morphine (3.5 mg/kg/day, subcutaneous [s.c.]) or saline for 5 days beginning on pregnancy day 17. On day 5 of lactation, animals were acutely challenged with morphine (0.5, 1.0, or 1.5 mg/kg, s.c.; MM0.5, MM1.0, and MM1.5 groups, respectively) or saline (MS group) and simultaneously tested for predatory hunting and maternal behavior. Control groups were pretreated with saline and challenged with morphine (SM0.5, SM1.0, and SM1.5 groups) or saline (SS group). Animals treated with morphine during late pregnancy and acutely challenged with 1.0 mg/kg morphine (MM1.0 group) exhibited significantly decreased maternal behavior and enhanced hunting. This effect was not evident for the 0.5 mg/kg dose. The 1.5 mg/kg morphine dose decreased maternal behavior and increased hunting in both the MM1.5 group and in animals acutely challenged with morphine after previous saline treatment (SM1.5 group). These results provide evidence of plasticity of the opioidergic role in behavioral selection during lactation.

As reações incondicionadas de defesa observadas em mamíferos são organizadas pelo Sistema Encefálico de Aversão (SEA), composto, entre outras estruturas, pela substância cinzenta periaquedutal dorsal (SCPd) e o colículo inferior (CI). Tem sido proposto que o CI seja parte do circuito sensoriomotor para os estímulos auditivos de natureza aversiva e a SCPd como a principal via de saída (output) do SEA para a elaboração de comportamentos defensivos. Ambas as estruturas são reguladas tonicamente pelo neurotransmissor inibitório ácido gama-aminobutírico (GABA). Este trabalho aborda a mediação química GABA/Benzodiazepínica (BZD) do processamento da informação aversiva no CI e das respostas de medo elaboradas pela SCPd. Grupos independentes de animais submetidos ao implante de quimitrodos (eletrodos acoplados a cânulas-guia para injeção de drogas) foram usados para avaliar no CI e SCPd os efeitos de injeções locais de muscimol (agonista de receptores GABA-A), semicarbazida (inibidor da síntese da enzima precursora do GABA descarboxilase do ácido glutâmico) ou midazolam (agonista BZD). Foram registrados potenciais evocados auditivos (PEA) no CI como medida eletrofisiológica da ativação neuronial, além da determinação dos limiares de congelamento e fuga, com o procedimento de estimulação elétrica (EE), tanto do CI quanto da SCPd. A mesma abordagem farmacológica com injeções de drogas intra-CI foi empregada em animais submetidos ao teste do Labirinto em Cruz Elevado (LCE), um modelo animal tradicional de ansiedade. Adicionalmente, investigou-se a participação de ambas as estruturas na expressão do comportamento de desligar uma luz de intensidade aversiva em um novo teste de medo incondicionado (Light Switch Off Test; LSOT) recentemente proposto pelo nosso grupo. Encontramos uma clara segregação funcional entre a porção dorsal e ventral do CI, sendo a última envolvida nos comportamentos defensivos. Mecanismos GABAérgicos em ambas as estruturas influenciam a amplitude do PEA e o congelamento pós-fuga da EE, sugerindo uma relação funcional entre as duas estruturas. Já no LSOT, os resultados indicam o envolvimento de mecanismos GABAérgicos do vCI, mas não da SCPd, na modulação da resposta incondicionada à luz em ratos. Os resultados obtidos permitem ampliar o conhecimento atual sobre a neurobiologia dos estados de medo e ansiedade, em uma abordagem integrada dos mecanismos de processamento das informações sensoriais e da expressão de reações de defesa. / Unconditioned defense reactions observed in mammals are organized by the Brain Aversive System, comprising, among other structures, the dorsal periaqueductal gray matter (dPAG) and the inferior colliculus (IC). It has been proposed that the IC is part of the sensorimotor circuitry that processes aversive auditory information and the dPAG is considered the main neural substrate for the expression of defensive behaviors. Both structures are tonically regulated by the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). This work addresses the chemical mediation of GABA/Benzodiazepine (BZD) on aversive information processing in the IC and the elaboration of fear responses by dPAG. Independent groups of animals implanted with chemitrodes (electrodes attached to a guide cannula for drug injection) have been used to evaluate the IC and dPAG regarding the effects of local injections of GABAergic agents (muscimol, semicarbazide, and midazolam). Auditory evoked potentials (AEP) have been recorded in the IC as a measure of electrophysiological neuronal activation, in addition to determining the thresholds of defensive freezing and flight behaviors, using the electrical stimulation (EE) procedure in both IC and dPAG. The same pharmacological regimen of drug injections intra-dPAG and intra-CI have been applied to animals subjected to the elevated plus maze (EPM), a well-known animal model of anxiety, and also to a novel animal test for innate fear (Light Switch Off Test, LSOT) that has been developed and proposed by our group. We found a clear functional segregation between the dorsal and ventral portions of the IC, the latter being the specific collicular substrate of defensive behaviors. GABAergic mechanisms in both structures influence the amplitude of the AEP and post-stimulation freezing of EE, suggesting a functional link between the two structures. In the LSOT, our data indicate the involvement of GABAergic mechanisms of the ICv, but not the dPAG, in the modulation of the unconditioned response to light in rats. These original findings presented here contribute to broaden the current knowledge on the neurobiology of fear and anxiety, in an integrative approach of the mechanisms underlying sensory processing and the expression of defensive behaviors.

O tratamento com morfina ao final da prenhez, faz com que uma única dose dessa droga durante a lactação iniba o comportamento maternal e estimule a caça predatória. A intensidade dessa mudança comportamental depende da dose desafio de morfina utilizada. A exposição a drogas de abuso pode levar a um fenômeno denominado tolerância reversa, que consiste na exacerbação dos efeitos do tratamento agudo com um fármaco observada após a interrupção de um tratamento crônico. O objetivo deste estudo foi avaliar como os efeitos do pré-tratamento com morfina durante a gestação podem influenciar na seleção comportamental após o parto. Ratas foram expostas simultaneamente a filhotes e insetos, sendo observada a expressão dos comportamentos maternal e predatório. As ratas foram tratadas com injeções diárias de morfina (3,5 mg/Kg, s.c.) do 17º ao 21º dia de gestação, e desafiadas agudamente no 5o ou 6o dia de lactação com doses distintas de morfina (0,5, 1,0 e 1,5mg/Kg; grupos MM0,5, MM1,0 e MM1,5) ou salina (grupo MS). Grupos controle foram pré-tratados com salina e desafiados com morfina (0,5, 1,0 e 1,5mg/Kg; grupos SM0,5, SM1,0 e SM1,5) ou salina (grupo SS), respectivamente. Em seguida foram testadas no paradigma de escolha entre cuidar dos filhotes e caçar. Animais pré-tratados com morfina e desafiados com 1,0 mg/Kg tiveram parâmetros de comportamento maternal prejudicados e facilitação ao comportamento de caça de maneira significante, o que não foi observado nos animais desafiados com a dose de 0,5 mg/Kg. Animais desafiados com 1,5 mg/Kg de morfina tiveram prejuízo em relação ao comportamento maternal e facilitação do comportamento predatório tanto no grupo de fêmeas pré-tratadas com morfina, quanto com salina. Em ratas lactantes a exposição simultânea a filhotes e insetos permitiu revelar a existência de tolerância reversa à mudança comportamental induzida por estímulo opioidérgico. / Treatment of postpartum female rats with morphine inhibits maternal behavior. The same treatment also stimulates foraging in adult animals. Exposure to drugs of abuse may result in a progressive and enduring enhancement of their reinforcing effects. Puerperal treatment with morphine leads to reverse tolerance to this drug, ultimately influencing the effects of opiates on maternal behavior. The aim of the present study was to investigate whether abrupt withdrawal from repeated morphine treatment during late pregnancy may influence the effects of morphine on behavioral selection in lactating rats. Animals were exposed simultaneously to pups and insects, and the choice between taking care of the pups and hunting for insects was observed. Female Wistar rats were treated with morphine (3.5 mg/kg/day, subcutaneous [s.c.]) or saline for 5 days beginning on pregnancy day 17. On day 5 of lactation, animals were acutely challenged with morphine (0.5, 1.0, or 1.5 mg/kg, s.c.; MM0.5, MM1.0, and MM1.5 groups, respectively) or saline (MS group) and simultaneously tested for predatory hunting and maternal behavior. Control groups were pretreated with saline and challenged with morphine (SM0.5, SM1.0, and SM1.5 groups) or saline (SS group). Animals treated with morphine during late pregnancy and acutely challenged with 1.0 mg/kg morphine (MM1.0 group) exhibited significantly decreased maternal behavior and enhanced hunting. This effect was not evident for the 0.5 mg/kg dose. The 1.5 mg/kg morphine dose decreased maternal behavior and increased hunting in both the MM1.5 group and in animals acutely challenged with morphine after previous saline treatment (SM1.5 group). These results provide evidence of plasticity of the opioidergic role in behavioral selection during lactation.