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      Controle autonômico da freqüência cardíaca em Spilotes pullatus (Colubridae) como determinante das respostas de medo Translated title: Autonomic control of heart rate in Spilotes pullatus (Colubridae) as determinant of fear responses

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          Abstract

          Neste estudo, investigaram-se as modificações fisiológicas em Spilotes pullatus, como determinantes das respostas ao medo, obtidas pela exposição ao eletrocardiograma. Foram utilizadas quatro serpentes com média de peso de 0,5±0,06kg. Dois minutos após a fixação dos eletrodos, as serpentes apresentavam-se imóveis, com redução significativa na freqüência cardíaca e aumento nos intervalos PQ, QRS, RR e RT (P<0,05). Os resultados sugerem que a presença de sintomas de medo pode gerar riscos à saúde desses animais.

          Translated abstract

          This study investigated electrocardiographic changes in Spilotes pullatus using four snakes weighing 0.5±0.06kg. Two minutes after that electrocardiogram apparatus had been fixed in Spilotes pullatus, snakes were immobile and there was a significant reduction of the heart rate and an increase in PQ, QRS, RR, and RT intervals (P<0.05). Results suggest that the presence of fear symptoms may represent a risk to the health of snakes.

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          Most cited references12

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          Conditioned neuroendocrine and cardiovascular stress responsiveness accompanying behavioral passivity and activity in aged and in young rats.

          Mean arterial pressure (MAP), heart rate (HR), plasma epinephrine (E), plasma norepinephrine (NE), and plasma corticosterone (CORT) were measured in 3-month- and 24-month-old male Wistar rats exposed to a conditioned emotional stress response (CER) paradigm and a conditioned defensive burying (CDB) paradigm. In the CER situation blood samples were taken during reexposure to the training environment one day after a single inescapable footshock (0.6 mA, AC for 3 s) had been administered. In the CER paradigm the young rats displayed passive behavior (immobility) accompanied by an increase in plasma levels of CORT and E, whereas both the control and conditioned animals showed increased NE responses. Previously shocked aged rats exhibited an attenuated plasma NE response, whereas levels of E remained elevated to a greater extent. Aged animals showed elevated basal levels of CORT one day after footshock administration. Stress-induced immobility was preserved in the aged rats. These animals had an increase in basal MAP values and a decrease in basal HR values compared to young ones. In the CDB paradigm, rats were exposed to a nonelectrified probe 1 day after the repeated shock (2 mA/contact) procedure. Young rats displayed defensive burying accompanied by increments in MAP, HR, CORT, and NE. The aged animals showed similar hormonal, autonomic, and behavioral stress responses. Thus, the age-related alterations in neuroendocrine and autonomic response patterns are apparent in stressed animals during behavioral passivity in absence of control (CER) rather than during active control (defensive burying).
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            Conditioned fear-induced tachycardia in the rat: vagal involvement.

            The effects of conditioned fear on gross activity, heart rate, PQ interval, noradrenaline and adrenaline were studied in freely moving rats. Subcutaneous (s.c.) injections of atropine methyl nitrate (0.5 mg/kg) during rest resulted in a significant shortening of the PQ interval, indicating that the PQ interval can be used as a measure of vagal activity. Conditioned fear was induced by 10-min forced exposure to a cage in which the rat had previously experienced footshocks (5 x 0.5 mA x 3 s). In non-shocked controls, an increase in gross activity was found and a pronounced tachycardia, without changes in PQ interval. Conditioned fear rats showed immobility behaviour, associated with a less pronounced tachycardia and an increase in PQ interval. Noradrenaline was similarly increased in both groups, whereas adrenaline was increased in conditioned fear rats only. To further evaluate the role of the vagus, rats were exposed to conditioned fear after pre-treatment with atropine methyl nitrate (0.5 mg/kg, s.c.). Again, immobility was observed with a concomitant tachycardia, but without an increase in PQ interval. These results indicate that the autonomic nervous system is differentially involved in heart rate regulation in conditioned fear rats and in non-shocked controls: in non-shocked controls a predominant sympathetic nervous system activation results in an increase in heart rate, whereas in conditioned fear rats the tachycardiac response is attenuated by a simultaneous activation of sympathetic nervous system and parasympathetic nervous system.
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              Cardiovascular and behavioural components of conditioned fear to context after ganglionic and alpha-adrenergic blockade.

              This study investigates the contribution of the peripheral nervous system to the cardiovascular component of long lasting (40 min) conditioned fear responses to context. The conditioned fear response evoked by reexposure to a footshock chamber was tested 10 min after intravenous injection of either the nicotinic ganglion blocker chlorisondamine (0.6 mg/kg) or the alpha-adrenoceptor antagonist phentolamine (10 mg/kg) in six rats implanted with telemetric probes. Compared to saline controls, chlorisondamine did not change the behavioural component of the response (freezing, ultrasonic vocalizations) but almost completely abolished its cardiovascular component (mean arterial pressure and heart rate). Phentolamine also abolished the pressor response but increased the cardiac response, and ultrasonic vocalizations were reduced by half. The results indicate that the long lasting pressor response of conditioned fear to context is sympathetically mediated like the much shorter pressor response of conditioned fear to a discrete stimulus.
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                Author and article information

                Journal
                abmvz
                Arquivo Brasileiro de Medicina Veterinária e Zootecnia
                Arq. Bras. Med. Vet. Zootec.
                Universidade Federal de Minas Gerais, Escola de Veterinária (Belo Horizonte, MG, Brazil )
                0102-0935
                1678-4162
                December 2008
                : 60
                : 6
                : 1468-1471
                Affiliations
                [01] Blumenau SC orgnameFURB orgdiv1CCEN orgdiv2Departamento de Ciências Naturais
                Article
                S0102-09352008000600024 S0102-0935(08)06000624
                3b853d2f-5ca8-4737-95af-371792a1b791

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 15 October 2007
                : 20 September 2008
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 12, Pages: 4
                Product

                SciELO Brazil

                Self URI: Texto completo somente em PDF (PT)
                Categories
                Medicina Veterinária

                bradycardia,electrocardiogram,snake,serpente,caninana,medo,eletrocardiograma,bradicardia,fear

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