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Os efeitos dos canabinoides em algumas áreas encefálicas que expressam receptores endocanabinoides, como é o caso dos núcleos hipotalâmicos, não são ainda muito bem definidos. Vários estudos têm demonstrado o papel de alguns núcleos hipotalâmicos na organização das reações induzidas pelo medo inato e pelo pânico. As respostas de defesa induzidas pelo medo instintivo caracterizam-se por serem mais elaboradas e dirigidas para algum abrigo ou rota de fuga. O estado de pânico pode ser provocado experimentalmente em animais de laboratório através da diminuição da atividade do sistema GABAérgico. O objetivo deste trabalho foi estudar os padrões comportamentais de fuga elaborada induzidos pelo bloqueio de receptores GABAérgicos do tipo A, com microinjeções intra-hipotalâmicas de bicuculina (BIC), especificamente na divisão dorso-medial do hipotálamo ventro-medial (VMHDM), assim como estabelecer o envolvimento endocanabinoides e o papel do receptor canabinoide do tipo 1 (CB1) na modulação das respostas defensivas organizadas pelo hipotálamo medial. Os resultados mostraram que a administração prévia de doses intermediárias (5pmol) de anandamida (AEA) atenuaram as respostas defensivas induzidas pela microinjeção intra-VMHDM de bicuculina (40ng), efeito este prevenido pelo pré-tratamento intra-hipotalâmica com antagonista de receptores CB1. Os resultados indicam que a AEA pode modular os efeitos pró-aversivos da bicuculina no VMHDM por meio do recrutamento de receptores CB1. / The effects of cannabinoids in some brain areas that express endocannabinoid receptors, such as some hypothalamic nuclei, are not yet well known. Several studies have demonstrated a role of hypothalamic nuclei in the organisation of behavioural responses induced by innate fear and panic attacks. The defensive responses induced by instinctive fear are more elaborated and oriented toward a burrow or alternative route of escape. Panic-prone states are able to be experimentally induced in laboratory animals decreasing the GABAergic system activity. The aim of this work was to study panic-like elaborated defensive behaviour evoked by GABAA receptor blockade with bicuculline (BIC) in the dorsomedial division of the ventromedial hypothalamus (VMHDM), we also aimed to establish the involvement of endocannabinoids and the role of CB1 cannabinoid receptor in the modulation of elaborated defense behavioural responses organised by medial hypothalamus. The results showed that intra-hypothalamic administration of anandamide (AEA) at the intermediate dose (5pmol) attenuated defensive responses induced by intra-VMHDM microinjection of bicuculline (40ng). This effect, however, was prevented by the pre-treatment of VMHDM with the CB1 receptor antagonist AM251. These results indicate that AEA can modulate the pro-aversive effects of bicuculline into the VMHDM, recruiting CB1 receptors.

Os efeitos dos canabinoides em algumas áreas encefálicas que expressam receptores endocanabinoides, como é o caso dos núcleos hipotalâmicos, não são ainda muito bem definidos. Vários estudos têm demonstrado o papel de alguns núcleos hipotalâmicos na organização das reações induzidas pelo medo inato e pelo pânico. As respostas de defesa induzidas pelo medo instintivo caracterizam-se por serem mais elaboradas e dirigidas para algum abrigo ou rota de fuga. O estado de pânico pode ser provocado experimentalmente em animais de laboratório através da diminuição da atividade do sistema GABAérgico. O objetivo deste trabalho foi estudar os padrões comportamentais de fuga elaborada induzidos pelo bloqueio de receptores GABAérgicos do tipo A, com microinjeções intra-hipotalâmicas de bicuculina (BIC), especificamente na divisão dorso-medial do hipotálamo ventro-medial (VMHDM), assim como estabelecer o envolvimento endocanabinoides e o papel do receptor canabinoide do tipo 1 (CB1) na modulação das respostas defensivas organizadas pelo hipotálamo medial. Os resultados mostraram que a administração prévia de doses intermediárias (5pmol) de anandamida (AEA) atenuaram as respostas defensivas induzidas pela microinjeção intra-VMHDM de bicuculina (40ng), efeito este prevenido pelo pré-tratamento intra-hipotalâmica com antagonista de receptores CB1. Os resultados indicam que a AEA pode modular os efeitos pró-aversivos da bicuculina no VMHDM por meio do recrutamento de receptores CB1. / The effects of cannabinoids in some brain areas that express endocannabinoid receptors, such as some hypothalamic nuclei, are not yet well known. Several studies have demonstrated a role of hypothalamic nuclei in the organisation of behavioural responses induced by innate fear and panic attacks. The defensive responses induced by instinctive fear are more elaborated and oriented toward a burrow or alternative route of escape. Panic-prone states are able to be experimentally induced in laboratory animals decreasing the GABAergic system activity. The aim of this work was to study panic-like elaborated defensive behaviour evoked by GABAA receptor blockade with bicuculline (BIC) in the dorsomedial division of the ventromedial hypothalamus (VMHDM), we also aimed to establish the involvement of endocannabinoids and the role of CB1 cannabinoid receptor in the modulation of elaborated defense behavioural responses organised by medial hypothalamus. The results showed that intra-hypothalamic administration of anandamide (AEA) at the intermediate dose (5pmol) attenuated defensive responses induced by intra-VMHDM microinjection of bicuculline (40ng). This effect, however, was prevented by the pre-treatment of VMHDM with the CB1 receptor antagonist AM251. These results indicate that AEA can modulate the pro-aversive effects of bicuculline into the VMHDM, recruiting CB1 receptors.

Prior work has shown important effects of the early life environment on development of adult stress response systems in both rats and humans. The present thesis is based on experiments that attempt to explore: 1) adolescent stress responding at hormonal and behavioural levels, and 2) the effects of repeated adolescent stressor exposure on adult stress responding (hormonal and behavioural) and levels of dopamine receptors expressed in prefrontal cortex, using both male and female rats. Defensive behaviours exhibited during stressor exposure and post-stress levels of circulating corticosterone were quantified as behavioural and hormonal measures of stress responding, respectively. In the first study, responses were compared among groups of adolescent rats exposed repeatedly to one of two different types of cat odour stressor stimuli (J-cloth coated in hair/dander or cat collar previously worn by a cat) or control stimuli, and long-term outcomes were examined in adulthood. Adolescent rats showed behavioural responses to both stressor stimuli, but behavioural inhibition was more consistent using repeated cat collar exposure, and this treatment resulted in long-term increases in anxiety-like behaviour in adulthood, whereas a stress-induced adolescent corticosterone elevation was observed only in the group that received exposure to the J-cloth stimuli. In the second study, adolescent and adult rats were compared directly using repeated exposure to the cat collar stressor or control stimuli. Adolescents were found to be more sensitive to the effects of the stressor stimuli, relative to adults. Finally, in the third study, repeated exposure to the J-cloth stressor or control stimuli was used, and stressor-exposed females showed elevated baseline corticosterone levels prior to the final exposure. Furthermore, stressor-exposed males and females showed lower levels of the D2 dopamine receptor in infralimbic and dorsopeduncular cortices of the prefrontal cortex in adulthood. In addition, these studies together provide evidence that sex differences in corticosterone levels emerge during the adolescent period. It may be concluded that adolescence should be considered a sensitive developmental timeframe for stress response programming.

Over 50% of the world’s human population resides in urban centres, and this is expected to increase as the global human population grows and people migrate from non-urban to urban centres. Concentrated in these urban areas are anthropogenic disturbances that impose additional challenges on wildlife compared to their non-urban counterparts. These challenges can be stress provoking. Through the release of corticosterone (CORT) reptiles can adapt to these stressors, physiologically and behaviourally, both in the short- and long-term. To investigate the relationships between stress activation and defensive tactics in wild urban Northwestern Gartersnakes (Thamnophis ordinoides) I conducted visual encounter surveys, along edge-focused transects, following a semi-constrained random sampling method. I sampled snakes at five sites, each with a different level of anthropogenic disturbance, in the Greater Victoria Area, BC. I sampled blood, observed anti-predator behaviour, and collected data on characteristics of snakes. The most disturbed site (with the most people, pets, and natural predators) also had the most snakes: those snakes also had highest H:L values (a proxy of CORT) in their blood compared to the other populations. Nevertheless, none of the snakes had H:L values that indicated chronic stress. Stress physiology was not correlated with anti-predator behaviour. More important to anti-predator behaviour was the size, sex/reproductive condition, and cloacal temperature of snakes. Although anthropogenic development can reduce habitat quality for some reptiles, Northwestern Gartersnakes coexist with recreationists at many sites in the District of Saanich. A multi-disciplinary approach is of paramount importance to understand the full effect of anthropogenic influences on wildlife. / Graduate / 0433 / 0329

Há evidências de que os endocanabinoides e os receptores CB1 estejam envolvidos em diversos transtornos emocionais, dentre eles a ansiedade e a depressão. A interação deste sistema endocanabinoide com outros neurotransmissores, como a serotonina (5-HT), tem sido alvo de diversos estudos, uma vez que o aumento na atividade deste sistema promove respostas ansiolíticas e antidepressivas. Alguns estudos mostraram que a porção ventromedial do hipotálamo modula algumas respostas defensivas, como fuga e a imobilidade tônica, respostas estas eliciadas pelos animais frente a situações de medo intenso, como ocorre em um confronto com um dado predador. Dentro desta perspectiva, o presente estudo teve por objetivos avaliar o efeito do tratamento crônico durante 21 dias com canabidiol (CBD) sobre as respostas defensivas em cobaias (Cavia porcellus), evocadas diante de um predador natural. Avaliamos, ainda, o efeito da microinjeção intradiencefálica de AM251 (antagonista de receptores CB1; 100pmol/0,2µl), de 6-I-CPS (antagonista de canais iônicos TRPV1; 9nmol/0,2µl), de WAY-100635 (antagonista 5-HT1A; 0,37nmol/0,2µl) e seus respectivos veículos em diferentes grupos de cobaias, após o tratamento crônico com canabidiol sobre as respostas defensivas evocadas diante do predador. Os resultados mostraram que, muito embora o tratamento crônico com CBD não tenha atenuado a resposta de imobilidade tônica (IT), devido ao fenômeno de habituação da resposta, diminuiu a expressão de outras respostas comportamentais, como a atenção defensiva e afuga orientada para a toca, promovendo, pois, um efeito anxiolítico e panicolítico. Ademais, a microinjeção de AM251 tendeu a abolir o efeito ansiolítico causado pelo tratamento crônico com CBD, potencializando as respostas defensivas diante de um predador natural. Tais resultados indicam que o CBD promove seu efeito farmacológico também mediante tratamento crônico, e que os receptores canabinoides do tipo CB1 do hipotálamo ventromedial parecem desmpenhar algum um papel nesse mecanismo de ação. / Evidence has shown that endocannabinoids and CB1 receptors are involved in several emotional disorders, including anxiety and depression. The endocannabinoid system and its interaction with other neurotransmitters such as serotonin (5-HT) has been the subject of several studies, since the increase in the activity of this system promotes anxiolytic and antidepressant responses. Some studies have shown that the ventromedial division of the hypothalamus modulates some defensive responses such as flight and tonic immobility, elicited by preys experiencing intense fear-like reactions when facing dangerous situations, as confrontation with a given predator. From this perspective, this study aimed to evaluate the effect of chronic treatment for 21 days with cannabidiol (CBD) on the defensive responses displayed by guinea pigs (Cavia porcellus), in the presence of a natural predator. We also studied the effect of intradiencephalic microinjection of AM251 (a CB1 receptor antagonist; 100pmol / 0.2?L), 6-PSC-I (TRPV1 ion channel antagonist; 9nmol / 0.2?L), or WAY- 100635 (antagonist 5- HT1A; 0.37nmol / 0.2?L) and their respective controls in different groups of mice after chronic treatment with cannabidiol on the defensive responses evoked in the presence of the predator. The results showed that although the chronic treatment with CBD attenuated tonic immobility response (IT) and other behavioural responses, such as defensive attention and oriented escape behaviour, promoting a significant anxiolytic and panicolytic effect. In addition, intra-hypothalamic microinjection of AM251 exert a potential impairment of the antipanic effect caused by chronic treatment with CBD, increasing the defensive responses displayed in the presence of the predator. These results indicate that the CBD also promotes its pharmacological effect upon chronic treatment, and that medial hypothalamus CB1 receptors seem to play a role in its mechanism of action.

Our senses are constantly bombarded with information. How does the brain integrate such a variety of inputs to generate appropriate behaviours? Innate defensive behaviours are a good model to address this question. They are essential for animal survival and the brain circuits that control them are highly conserved across species. Moreover, the sensory inputs and behavioural outputs can be well defined and reliably reproduced in the lab. This allows us to study function of the individual components of the circuit controlling these behaviours. Ventromedial hypothalamus (VMH) is a key brain region for controlling responses to predators; it has been shown that inactivating the VMH can reduce defensive behaviours. Interestingly, activating the VMH output neurons (SF1+ cells) can produce a variety of different behaviours, from immobility to escape, depending on the intensity of activation. During my PhD I used a variety of approaches to address the question of the function of the VMH in control of defensive behaviours. At first I hypothesised that the VMH might act as a centre responsible for choosing an appropriate behavioural response according to the stimulus. I set to investigate how different activation levels of SF1+ neurons can produce such different behavioural outputs, and how this activity is modulated in vivo in response to predator stimuli. I began the project by quantifying mouse defensive behaviours in response to olfactory and auditory predator cues, as well as to the optogenetic activation of SF1+ neurons. I then questioned whether there was heterogeneity within the population of SF1+ neurons, which could explain their ability to trigger different behaviours. I performed patch clamp recordings from acute brain slices and conducted a study of the electrophysiological properties of SF1+ neurons. I next investigated how SF1+ neurons integrate excitatory inputs from the medial amygdala, a region which receives olfactory inputs from the accessory olfactory bulb. By combining optogenetics with slice electrophysiology and behavioural assessment, I described the physiology and relevance of this connection. Finally, I investigated in vivo activity in the VMH in response to predator cues by performing calcium imaging of the VMH neurons in freely moving mice. By presenting different sensory stimuli, I addressed the question of heterogeneity of the input pattern to the VMH neurons and the relationship between the VMH activity and the behavioural output. Taken all together, the results of this project have led to a hypothesis whereby the function of the VMH is to facilitate rather than directly control the choice of an appropriate behavioural response.

Há evidências de que os endocanabinoides e os receptores CB1 estejam envolvidos em diversos transtornos emocionais, dentre eles a ansiedade e a depressão. A interação deste sistema endocanabinoide com outros neurotransmissores, como a serotonina (5-HT), tem sido alvo de diversos estudos, uma vez que o aumento na atividade deste sistema promove respostas ansiolíticas e antidepressivas. Alguns estudos mostraram que a porção ventromedial do hipotálamo modula algumas respostas defensivas, como fuga e a imobilidade tônica, respostas estas eliciadas pelos animais frente a situações de medo intenso, como ocorre em um confronto com um dado predador. Dentro desta perspectiva, o presente estudo teve por objetivos avaliar o efeito do tratamento crônico durante 21 dias com canabidiol (CBD) sobre as respostas defensivas em cobaias (Cavia porcellus), evocadas diante de um predador natural. Avaliamos, ainda, o efeito da microinjeção intradiencefálica de AM251 (antagonista de receptores CB1; 100pmol/0,2µl), de 6-I-CPS (antagonista de canais iônicos TRPV1; 9nmol/0,2µl), de WAY-100635 (antagonista 5-HT1A; 0,37nmol/0,2µl) e seus respectivos veículos em diferentes grupos de cobaias, após o tratamento crônico com canabidiol sobre as respostas defensivas evocadas diante do predador. Os resultados mostraram que, muito embora o tratamento crônico com CBD não tenha atenuado a resposta de imobilidade tônica (IT), devido ao fenômeno de habituação da resposta, diminuiu a expressão de outras respostas comportamentais, como a atenção defensiva e afuga orientada para a toca, promovendo, pois, um efeito anxiolítico e panicolítico. Ademais, a microinjeção de AM251 tendeu a abolir o efeito ansiolítico causado pelo tratamento crônico com CBD, potencializando as respostas defensivas diante de um predador natural. Tais resultados indicam que o CBD promove seu efeito farmacológico também mediante tratamento crônico, e que os receptores canabinoides do tipo CB1 do hipotálamo ventromedial parecem desmpenhar algum um papel nesse mecanismo de ação. / Evidence has shown that endocannabinoids and CB1 receptors are involved in several emotional disorders, including anxiety and depression. The endocannabinoid system and its interaction with other neurotransmitters such as serotonin (5-HT) has been the subject of several studies, since the increase in the activity of this system promotes anxiolytic and antidepressant responses. Some studies have shown that the ventromedial division of the hypothalamus modulates some defensive responses such as flight and tonic immobility, elicited by preys experiencing intense fear-like reactions when facing dangerous situations, as confrontation with a given predator. From this perspective, this study aimed to evaluate the effect of chronic treatment for 21 days with cannabidiol (CBD) on the defensive responses displayed by guinea pigs (Cavia porcellus), in the presence of a natural predator. We also studied the effect of intradiencephalic microinjection of AM251 (a CB1 receptor antagonist; 100pmol / 0.2?L), 6-PSC-I (TRPV1 ion channel antagonist; 9nmol / 0.2?L), or WAY- 100635 (antagonist 5- HT1A; 0.37nmol / 0.2?L) and their respective controls in different groups of mice after chronic treatment with cannabidiol on the defensive responses evoked in the presence of the predator. The results showed that although the chronic treatment with CBD attenuated tonic immobility response (IT) and other behavioural responses, such as defensive attention and oriented escape behaviour, promoting a significant anxiolytic and panicolytic effect. In addition, intra-hypothalamic microinjection of AM251 exert a potential impairment of the antipanic effect caused by chronic treatment with CBD, increasing the defensive responses displayed in the presence of the predator. These results indicate that the CBD also promotes its pharmacological effect upon chronic treatment, and that medial hypothalamus CB1 receptors seem to play a role in its mechanism of action.

Há estudos que mostraram que o ácido N-metil-D-aspártico (NMDA), microinjetado nas estruturas do teto mesencefálico (corpos quadrigêmeos) de ratos evoca comportamentos defensivos do tipo pânico que podem ser seguidos por uma resposta antinociceptiva. Tem sido sugerido que respostas defensivas relacionadas ao medo organizadas por neurônios do tronco cerebral podem ser moduladas por projeções ascendentes mediadas pelo neurotransmissor 5-hidroxitriptamina (5-HT) do núcleo dorsal da rafe (NDR), e fenômenos antinociceptivos induzidos pelo medo inato podem ser organizados por vias serotoninérgicas descendentes também originadas no NDR. Os neurônios do NDR que originam tais conexões, por sua vez, podem ser moduladas por monoaminas que recrutam receptores 5-HT2A localizados no NDR. Não obstante, háuma escassez de estudos mostrando o papel dos receptores 5-HT2A do NDR na modulação do comportamento do tipo pânico e da antinocicepção induzida pelo medo inato organizados nos colículos superiores e inferiores. O objetivo deste estudo foi investigar a participação dos receptores 5-HT2A do NDR na modulação do comportamento de defesa organizado pelos corpos quadrigêmeos e da antinocicepção induzida pelo medo evocados por microinjeções de NMDA nos corpos quadrigêmeos. No experimento I, os animais receberam microinjeção de veículo (NaCl 0,9% / 0,2?L) ou 6, 9 e 12 nmol NMDA no CI. No experimento II, foi realizado o pré-tratamento do NDR com microinjeções de veículo ou o antagonista seletivo do receptor 5HT2A (R-96544) nas concentrações de 5, 10 e 15 nM. Dez minutos depois, o NMDA na dose mais efetiva (12 nmol) foi injetado no CI. Em ambos os experimentos, as respostas defensivas foram analisadas quantitativamente durante 10 min e, em seguida, as latências de retirada de cauda foram medidas a intervalos de 10 min durante 70 min. No experimento III, os animais receberam microinjeção de salina fisiológica ou NMDA (6, 9 e 12 nmol) nas cpSC. No experimento IV, a dose mais efetiva de NMDA (12 nmol) ou veículo foi precedida por microinjeções de veículo ou antagonista seletivo do receptor 5HT2A (R- 96544) em diferentes concentrações, 0.5, 5 e 10 nM. Ambos os efeitos pró-eversivos e antinociceptivos provocados pelas injecções intra-cpCS de NMDA foram atenuados pelo pré-tratamento do NDR com R-96544. No experimento V, a análise morfológica mostrou que os receptores 5-HT2A estão presentes nos interneurônios GABAérgicos do NDR. Em conjunto, esses achados sugerem que o bloqueio dos receptores 5-HT2A no NDR é capaz de atenuar tanto o comportamento defensivo do tipo pânico quanto a antinocicepção induzida pelo medo organizada pelos corpos quadrigêmeos. / There are studies that suggest that N-methyl-D-aspartic acid (NMDA) microinjected into the midbrain tectum structures, such corpora quadrigemina, of rats evokes panic-like defensive behaviours that can be followed by an antinociceptive response. It has been suggested that fear-related defensive responses organised by brainstem neurons can be modulated by ascending projections mediated by the neurotransmitter 5-hydroxytryptamine (5-HT) of the dorsal raphe nucleus (DRN), and phenomena of innate fear-induced antinociception can be organised by descending serotonergic pathways also originating from the DRN. The DRN neurons that give rise to such connections, in turn, can be moduled by monoamines that recruit 5-HT2A receptors located in the DRN. Nevertheless, there is a shortage of studies showing the role of DRN 5-HT2A receptors in the modulation of panic-like behaviour and innate fearinduced antinociception organised by superior and inferior colliculi. The purpose of this study was to investigate the participation of DRN 5-HT2A receptors in the modulation of panic-like behaviour and antinociception evoked by corpora quadrigemina injections of NMDA. In experiment I, the animals received microinjection of vehicle (0.9%NaCl/0.2?L) or 6, 9 and 12 nmol NMDA into the IC. In experiment II, it was performed the pretreatment of DRN with microinjections of vehicle or the 5HT2A receptor selective antagonist (R-96544) in a concentration of 5, 10 and 15 nM. Ten minutes later, NMDA at the most effective dose (12nmol) was injected in the IC. In both experiments, the defensive responses were quantitatively analysed for 10 min and then the tail-flick withdrawal latencies were measured at 10 min-intervals for 70 min. In experiment III, the animals received microinjection of physiological saline or NMDA (6, 9 and 12 nmol) into the deep layers of SC (dlSC). In experiment IV, the most effective dose of NMDA (12 nmol) or vehicle was preceded by microinjections of vehicle or 5HT2A receptor selective antagonist (R-96544) at different concentrations (0.5, 5, and 10 nM). Both proaversive and antinociceptive effects elicited by intra-dlSC injections of NMDA were attenuated by the pretreatment of the DRN with R-96544. In experiment V, the morphological analysis showed that 5-HT2A receptors are present in GABAergic interneurons in the DRN. Taken together, these findings suggest that the blockade of DRN 5-HT2A receptors decreased both panic attack-like defensive behaviour and fear- induced antinociception organised by the corpora quadrigemina neurons.