Animal models of anxiety: an ethological perspective

In the field of anxiety research, animal models are used as screening tools in the search for compounds with therapeutic potential and as simulations for research on mechanisms underlying emotional behaviour. However, a solely pharmacological approach to the validation of such tests has resulted in distinct problems with their applicability to systems other than those involving the benzodiazepine/GABAA receptor complex. In this context, recent developments in our understanding of mammalian defensive behaviour have not only prompted the development of new models but also attempts to refine existing ones. The present review focuses on the application of ethological techniques to one of the most widely used animal models of anxiety, the elevated plus-maze paradigm. This fresh approach to an established test has revealed a hitherto unrecognized multidimensionality to plus-maze behaviour and, as it yields comprehensive behavioural profiles, has many advantages over conventional methodology. This assertion is supported by reference to recent work on the effects of diverse manipulations including psychosocial stress, benzodiazepines, GABA receptor ligands, neurosteroids, 5-HT1A receptor ligands, and panicolytic/panicogenic agents. On the basis of this review, it is suggested that other models of anxiety may well benefit from greater attention to behavioural detail

The use of non-human primates as animal models for the study of hepatitis viruses

Hepatitis viruses belong to different families and have in common a striking hepatotropism and restrictions for propagation in cell culture. The transmissibility of hepatitis is in great part limited to non-human primates. Enterically transmitted hepatitis viruses (hepatitis A virus and hepatitis E virus) can induce hepatitis in a number of Old World and New World monkey species, while the host range of non-human primates susceptible to hepatitis viruses transmitted by the parenteral route (hepatitis B virus, hepatitis C virus and hepatitis delta virus) is restricted to few species of Old World monkeys, especially the chimpanzee. Experimental studies on non-human primates have provided an invaluable source of information regarding the biology and pathogenesis of these viruses, and represent a still indispensable tool for vaccine and drug testing.

Transgenic animal models for the functional analysis of vasoactive peptides

The interplay of vasoactive peptide systems is an essential determinant of blood pressure regulation in mammals. While the endothelin and the renin-angiotensin systems raise blood pressure by inducing vasoconstriction and sodium retention, the kallikrein-kinin and the natriuretic-peptide systems reduce arterial pressure by eliciting vasodilatation and natriuresis. Transgenic technology has proven to be very useful for the functional analysis of vasoactive peptide systems. As an outstanding example, transgenic rats overexpressing the mouse Ren-2 renin gene in several tissues become extremely hypertensive. Several other transgenic rat and mouse strains with genetic modifications of components of the renin-angiotensin system have been developed in the past decade. Moreover, in recent years gene-targeting technology was employed to produce mouse strains lacking these proteins. The established animal models as well as the main insights gained by their analysis are summarized in this review.

The relationship between anxiety and depression in animal models: a study using the forced swimming test and elevated plus-maze

The present study evaluated the correlation between the behavior of mice in the forced swimming test (FST) and in the elevated plus-maze (PM). The effect of the order of the experiments, i.e., the influence of the first test (FST or PM) on mouse behavior in the second test (PM or FST, respectively) was compared to handled animals (HAND). The execution of FST one week before the plus-maze (FST-PM, N = 10), in comparison to mice that were only handled (HAND-PM, N = 10) in week 1, decreased % open entries (HAND-PM: 33.6 ± 2.9; FST-PM: 20.0 ± 3.9; mean ± SEM; P<0.02) and % open time (HAND-PM: 18.9 ± 3.3; FST-PM: 9.0 ± 1.9; P<0.03), suggesting an anxiogenic effect. No significant effect was seen in the number of closed arm entries (FST-PM: 9.5 (7.0-11.0); HAND-PM: 10.0 (4.0-14.5), median (interquartile range); U = 46.5; P>0.10). A prior test in the plus-maze (PM-FST) did not change % immobility time in the FST when compared to the HAND-FST group (HAND-FST: 57.7 ± 3.9; PM-FST: 65.7 ± 3.2; mean ± SEM; P>0.10). Since these data suggest that there is an order effect, the correlation was evaluated separately with each test sequence: FST-PM (N = 20) and PM-FST (N = 18). There was no significant correlation between % immobility time in the FST and plus-maze indexes (% time and entries in open arms) in any test sequence (r: -0.07 to 0.18). These data suggest that mouse behavior in the elevated plus-maze is not related to behavior in the forced swimming test and that a forced swimming test before the plus-maze has an anxiogenic effect even after a one-week interval.

The brain decade in debate: II. Panic or anxiety? From animal models to a neurobiological basis

This article is a transcription of an electronic symposium sponsored by the Brazilian Society of Neuroscience and Behavior (SBNeC). Invited researchers from the European Union, North America and Brazil discussed two issues on anxiety, namely whether panic is a very intense anxiety or something else, and what aspects of clinical anxiety are reproduced by animal models. Concerning the first issue, most participants agreed that generalized anxiety and panic disorder are different on the basis of clinical manifestations, drug response and animal models. Also, underlying brain structures, neurotransmitter modulation and hormonal changes seem to involve important differences. It is also common knowledge that existing animal models generate different types of fear/anxiety. A challenge for future research is to establish a good correlation between animal models and nosological classification.

Head-to-head comparison of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia in an animal model of coronary artery stenosis

To compare the sensitivity of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia we produced a physiologically significant stenosis in the left circumflex artery of 14 open-chest dogs (range: 50 to 89% reduction in luminal diameter). In each study, dobutamine (5 to 40 µg kg-1 min-1 in 3-min stages) and pacing (20 bpm increments, each 2 min, up to 260 bpm) were performed randomly, and then followed by dipyridamole (up to 0.84 mg/kg over 10 min). The positivity of stress echocardiography tests was quantitatively determined by a significant (P<0.05) reduction of or failure to increase absolute and percent systolic wall thickening in the stenotic artery supplied wall, as compared to the opposite wall (areas related to the left anterior descending artery). Systolic and diastolic frozen images were analyzed off-line by two blinded observers in the control and stress conditions. The results showed that 1) the sensitivity of dobutamine, dipyridamole and pacing stress tests was 57, 57 and 36%, respectively; 2) in animals with positive tests, the mean percent change of wall thickening in left ventricular ischemic segments was larger in the pacing (-19 ± 11%) and dipyridamole (-18 ± 16%) tests as compared to dobutamine (-9 ± 6%) (P = 0.05), but a similar mean reduction of wall thickening was observed when this variable was normalized to a control left ventricular segment (area related to the left anterior descending artery) (pacing: -16 ± 7%; dipyridamole: -25 ± 16%; dobutamine: -26 ± 10%; not significant), and 3) a significant correlation was observed between magnitude of coronary stenosis and left ventricular segmental dysfunction induced by ischemia in dogs submitted to positive stress tests. We conclude that the dobutamine and dipyridamole stress tests showed identical sensitivities for the detection of myocardial ischemia in this one-vessel disease animal model with a wide range of left circumflex artery stenosis. The pacing stress test was less sensitive, but the difference was not statistically significant. The magnitude of segmental left ventricular dysfunction induced by ischemia was similar in all stress tests evaluated.

The brain decade in debate: VI. Sensory and motor maps: dynamics and plasticity

This article is an edited transcription of a virtual symposium promoted by the Brazilian Society of Neuroscience and Behavior (SBNeC). Although the dynamics of sensory and motor representations have been one of the most studied features of the central nervous system, the actual mechanisms of brain plasticity that underlie the dynamic nature of sensory and motor maps are not entirely unraveled. Our discussion began with the notion that the processing of sensory information depends on many different cortical areas. Some of them are arranged topographically and others have non-topographic (analytical) properties. Besides a sensory component, every cortical area has an efferent output that can be mapped and can influence motor behavior. Although new behaviors might be related to modifications of the sensory or motor representations in a given cortical area, they can also be the result of the acquired ability to make new associations between specific sensory cues and certain movements, a type of learning known as conditioning motor learning. Many types of learning are directly related to the emotional or cognitive context in which a new behavior is acquired. This has been demonstrated by paradigms in which the receptive field properties of cortical neurons are modified when an animal is engaged in a given discrimination task or when a triggering feature is paired with an aversive stimulus. The role of the cholinergic input from the nucleus basalis to the neocortex was also highlighted as one important component of the circuits responsible for the context-dependent changes that can be induced in cortical maps.

A new model for the immobilization of the rat hind limb

An alternative device for the immobilization of the hind limb of the rat was developed to study the effects of chronic disuse on the soleus and tibialis anterior muscles, maintained for 3 weeks in the shortening and the stretching positions, respectively. The proposed device is made of steel mesh and cotton materials, and has some advantages when compared to cast or plaster cast: it is cheaper, lighter (12 g or 4% of the body weight of the rat) and the same unit can be easily adjusted and used several times in the same animal or in animals of similar size. Immobilization is also useful to restrain the movements of the hip, knee, and ankle joints. Male rats (291 ± 35 g and aged 14 ± 2 weeks) were used to develop and test the model. The soleus muscle of 18 rats was maintained in a shortened position for 21 consecutive days and lost 19 ± 7% of its length (P = 0.008) and 44 ± 6% of its weight (P = 0.002) compared to the contralateral intact muscle. No difference (P = 0.67) was found in the stretched tibialis anterior of the same hind limb when compared to the contralateral muscle. No ulcer, sore or foot swelling was observed in the animals. Immobilization was effective in producing chronic muscle disuse in the hind limbs of rats and is an acceptable alternative to the traditional methods of immobilization such as cast or plaster cast.

Reliability and clinical utility of a Portuguese version of the Abnormal Involuntary Movements Scale (AIMS) for tardive dyskinesia in Brazilian patients

The objective of the present study was to evaluate the reliability and clinical utility of a Portuguese version of the Abnormal Involuntary Movements Scale (AIMS). Videotaped interviews with 16 psychiatric inpatients treated with antipsychotic drugs for at least 5 years were evaluated. Reliability was assessed by the intraclass correlation coefficient (ICC) between three raters, two with and one without clinical training in psychopathology. Clinical utility was assessed by the difference between the scores of patients with (N = 11) and without (N = 5) tardive dyskinesia (TD). Patients with TD exhibited a higher severity of global evaluation by the AIMS (sum of scores: 4.2 ± 0.9 vs 0.4 ± 0.2; score on item 8: 2.3 ± 0.3 vs 0.4 ± 0.2, TD vs controls). The ICC for the global evaluation was fair between the two skilled raters (0.58-0.62) and poor between these raters and the rater without clinical experience (0.05-0.29). Thus, we concluded that the Portuguese version of the AIMS shows an acceptable inter-rater reliability, but only between clinically skilled raters, and that it is clinically useful.

Phenomena and mechanisms in purification of animal fat

Työn tarkoitus oli tutkia eläinrasvan puhdistusta biodieselin valmistusta varten. Eläinrasvaa syntyy elintarviketeollisuuden sivutuotteena ja sitä saadaan myös myymättä jääneistä elintarvikkeista. Rasva sisältää epäpuhtauksia, jotka on poistettava ennen biodieselprosessia. Tässä työssä tutkittavat epäpuhtaudet ovat typpi, fosfori, rauta, natrium, kalsium ja magnesium. Puhdistusmenetelminä käytettiin saostamista sitruunahapolla sekä adsorbointia kahdella eri adsorbentilla. Tavoitteena oli selvittää riittävä määrä happoa ja adsorbenttia sekä tutkia puhdistuksen mekanismia. Lisäksi tarkasteltiin lämpötilan vaikutusta adsorption aikana.

Can organic and transgenic soy be used as a substitute for animal protein by rats?

We evaluated the protein quality of organic and transgenic soy fed to rats throughout life. Thirty female Wistar rats were divided into three groups (N = 10): organic soy group (OSG) receiving organic soy-based diet, genetically modified soy group (GMSG) receiving transgenic soy-based diet, and a control group (CG) receiving casein-based diet. All animals received water and isocaloric diet (10% protein), ad libitum for 291 days. After this, the weight of GMSG animals (290.9 ± 9.1 g) was significantly lower (P <= 0.04) than CG (323.2 ± 7.9 g). The weight of OSG (302.2 ± 8.7 g) was between that of the GMSG and the CG. Protein intake was similar for OSG (308.4 ± 6.8 g) and GMSG (301.5 ± 2.5 g), and significantly lower (P <= 0.0005) than the CG (358.4 ± 8.1 g). Growth rate was similar for all groups: OSG (0.80 ± 0.02 g), GMSG (0.81 ± 0.03 g) and CG (0.75 ± 0.02 g). In addition to providing a good protein intake and inducing less weight gain, both types of soy were utilized in a manner similar to that of casein, suggesting that the protein quality of soy is similar to that of the standard protein casein. The groups fed soy-based diet gained less weight, which may be considered to be beneficial for health. We conclude that organic and transgenic soy can be fed throughout life to rats in place of animal protein, because contain high quality protein and do not cause a marked increase in body weight.

Effect of Erythrina velutina and Erythrina mulungu in rats submitted to animal models of anxiety and depression

Erythrina velutina (EV) and Erythrina mulungu (EM), popularly used in Brazil as tranquilizing agents, were studied. The effects of acute and chronic oral treatment with a water:alcohol extract of EV (7:3, plant grounded stem bark; acute = 100, 200, 400 mg/kg; chronic = 50, 100, 200 mg/kg) were evaluated in rats (N = 11-12) submitted to the elevated T-maze (for avoidance and escape measurements) model of anxiety. This model was selected for its presumed capacity to elicit specific subtypes of anxiety disorders recognized in clinical practice: avoidance has been related to generalized anxiety and escape to panic. Additionally, animals were treated with the same doses of EV and EM (water:alcohol 7:3, inflorescence extract) and submitted to the forced swim test for the evaluation of antidepressant activity (N = 7-10). Both treatment regimens with EV impaired elevated T-maze avoidance latencies, without altering escape, in a way similar to the reference drug diazepam (avoidance 1, mean ± SEM, acute study: 131.1 ± 45.5 (control), 9.0 ± 3.3 (diazepam), 12.7 ± 2.9 (200 mg/kg), 28.8 ± 15.3 (400 mg/kg); chronic study: 131.7 ± 46.9 (control), 35.8 ± 29.7 (diazepam), 24.4 ± 10.4 (50 mg/kg), 29.7 ± 11.5 (200 mg/kg)). Neither EV nor EM altered measurements performed in the forced swim test, in contrast to the reference drug imipramine that significantly decreased immobility time after chronic treatment. These results were not due to motor alterations since no significant effects were detected in an open field. These observations suggest that EV exerts anxiolytic-like effects on a specific subset of defensive behaviors which have been associated with generalized anxiety disorder.

Training-related changes in the R-R interval at the onset of passive movements in humans

The aim of the present study was to determine whether training-related alterations in muscle mechanoreflex activation affect cardiac vagal withdrawal at the onset of exercise. Eighteen male volunteers divided into 9 controls (26 ± 1.9 years) and 9 racket players (25 ± 1.9 years) performed 10 s of voluntary and passive movement characterized by the wrist flexion of their dominant and non-dominant limbs. The respiratory cycle was divided into four phases and the phase 4 R-R interval was measured before and immediately following the initiation of either voluntary or passive movement. At the onset of voluntary exercise, the decrease in R-R interval was similar between dominant and non-dominant forearms in both controls (166 ± 20 vs 180 ± 34 ms, respectively; P > 0.05) and racket players (202 ± 29 vs 201 ± 31 ms, respectively; P > 0.05). Following passive movement, the non-dominant forearm of racket players elicited greater changes than the dominant forearm (129 ± 30 vs 77 ± 17 ms; P < 0.05), as well as both the dominant (54 ± 20 ms; P < 0.05) and non-dominant (59 ± 14 ms; P < 0.05) forearms of control subjects. In contrast, changes in R-R interval elicited by the racket players' dominant forearm were similar to that observed in the control group, indicating that changes in R-R interval at the onset of passive exercise were not attenuated in the dominant forearm of racket players. In summary, cardiac vagal withdrawal induced by muscle mechanoreflex stimulation is well-maintained, despite long-term exposure to training.

The immunomodulator glatiramer acetate influences spinal motoneuron plasticity during the course of multiple sclerosis in an animal model

The immunomodulador glatiramer acetate (GA) has been shown to significantly reduce the severity of symptoms during the course of multiple sclerosis and in its animal model - experimental autoimmune encephalomyelitis (EAE). Since GA may influence the response of non-neuronal cells in the spinal cord, it is possible that, to some extent, this drug affects the synaptic changes induced during the exacerbation of EAE. In the present study, we investigated whether GA has a positive influence on the loss of inputs to the motoneurons during the course of EAE in rats. Lewis rats were subjected to EAE associated with GA or placebo treatment. The animals were sacrificed after 15 days of treatment and the spinal cords processed for immunohistochemical analysis and transmission electron microscopy. A correlation between the synaptic changes and glial activation was obtained by performing labeling of synaptophysin and glial fibrillary acidic protein using immunohistochemical analysis. Ultrastructural analysis of the terminals apposed to alpha motoneurons was also performed by electron transmission microscopy. Interestingly, although the GA treatment preserved synaptophysin labeling, it did not significantly reduce the glial reaction, indicating that inflammatory activity was still present. Also, ultrastructural analysis showed that GA treatment significantly prevented retraction of both F and S type terminals compared to placebo. The present results indicate that the immunomodulator GA has an influence on the stability of nerve terminals in the spinal cord, which in turn may contribute to its neuroprotective effects during the course of multiple sclerosis.

Animal model for age- and sex-related genotoxicity of diethylstilbestrol

Environmental xenoestrogens pose a significant health risk for all living organisms. There is growing evidence concerning the different susceptibility to xenoestrogens of developing and adult organisms, but little is known about their genotoxicity in pre-pubertal mammals. In the present study, we developed an animal model to test the sex- and age-specific genotoxicity of the synthetic estrogen diethylstilbestrol (DES) on the reticulocytes of 3-week-old pre-pubertal and 12-week-old adult BALB/CJ mice using the in vivo micronucleus (MN) assay. DES was administered intraperitoneally at doses of 0.05, 0.5, and 5 µg/kg for 3 days and animals were sampled 48, 72 and 96 h, and 2 weeks after exposure. Five animals were analyzed for each dose, sex, and age group. After the DES dose of 0.05 µg/kg, pre-pubertal mice showed a significant increase in MN frequency (P < 0.001), while adults continued to show reference values (5.3 vs 1.0 MN/1000 reticulocytes). At doses of 0.5 and 5 µg/kg, MN frequency significantly increased in both age groups. In pre-pubertal male animals, MN frequency remained above reference values for 2 weeks after exposure. Our animal model for pre-pubertal genotoxicity assessment using the in vivo MN assay proved to be sensitive enough to distinguish age and sex differences in genome damage caused by DES. This synthetic estrogen was found to be more genotoxic in pre-pubertal mice, males in particular. Our results are relevant for future investigations and the preparation of legislation for drugs and environmentally emitted agents, which should incorporate specific age and gender susceptibility.