The brain decade in debate: III. Neurobiology of emotion

This article is a transcription of an electronic symposium in which active researchers were invited by the Brazilian Society of Neuroscience and Behavior (SBNeC) to discuss the advances of the last decade in the neurobiology of emotion. Four basic questions were debated: 1) What are the most critical issues/questions in the neurobiology of emotion? 2) What do we know for certain about brain processes involved in emotion and what is controversial? 3) What kinds of research are needed to resolve these controversial issues? 4) What is the relationship between learning, memory and emotion? The focus was on the existence of different neural systems for different emotions and the nature of the neural coding for the emotional states. Is emotion the result of the interaction of different brain regions such as the amygdala, the nucleus accumbens, or the periaqueductal gray matter or is it an emergent property of the whole brain neural network? The relationship between unlearned and learned emotions was also discussed. Are the circuits of the former the underpinnings of the latter? It was pointed out that much of what we know about emotions refers to aversively motivated behaviors, like fear and anxiety. Appetitive emotions should attract much interest in the future. The learning and memory relationship with emotions was also discussed in terms of conditioned and unconditioned stimuli, innate and learned fear, contextual cues inducing emotional states, implicit memory and the property of using this term for animal memories. In a general way it could be said that learning modifies the neural circuits through which emotional responses are expressed

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

Alcohol dependence induced in rats by semivoluntary intermittent intake

The objetive of the present experiment was to assess ethyl alcohol (ETOH) dependence brought about by a semivoluntary intermittent intake regimen in rats. Male Wistar rats weighing 150-250 g at the onset of the experiment were assigned to the following groups: 0 percent ETOH (N = 11), 5 percent ETOH (N = 20), 20 percent ETOH (N = 20) and 40 percent ETOH (N = 18). ETOH solutions were offered at the end of the day and overnight from Monday to Friday, and throughout weekends, for 90 days. The concentration of the ETOH solutions was increased in a stepwise fashion allowing the rats to get used to the taste of alcohol. Reposition of pure water was permitted during 1-h water drinking periods in the morning. Daily volume intake (+ SEM) averaged 25.4 + 0.4 ml (0 percent ETOH), 23.8 + 0.6 ml (5 percent ETOH), 17.6 + 0.7 ml (20 percent ETOH) and 17.5 + 0.6 ml (40 percent ETOH). ETOH consumption differed significantly (P<0.05) among groups, averaging 4.4 + 0.2 g Kg(-1) day(-1) (5 percent ETOH), 10.3 + 0.3 g Kg(-1) day(-1) (20 percent ETOH) and 26 + 1.2 g kg(-1) day(-1) (40 percent ETOH). Furthermore, ETOH detection in plasma 10-12h after offering the solution indicated that its consumption in the 40 percent ETOH group was sufficient to override its metabolism. Overt signs of ETOH dependence, such as increased thirst, hyperactivity, puffing, hair ruffling and startle responsiveness as well as reduced drowsiness, were significantly increased in the 20 percent and 40 percent ETOH groups compared to the 0 percent and 5 percent groups. Accordingly, the model described here proved to be a useful tool for the evaluation of subtle or moderate behavioral and physical consequences of long-term ETOH intake.

Cardiovascular change in response to prolonged defense area stimulation in freely moving rats

The mean blood pressure and heart rate of freely moving rats were directly recorded over a 1-min period of electrical stimulation of the periaqueductal gray with intensities that induced freezing behavior, intense flight or no behavioral changes. Blood pressure and heart rate increased only when flight was induced and only during the first 15 s of stimulation. These cardiovascular changes suggest that homeostatic mechanisms act during the defense reaction and are markedly inhibited only at the beginning of the stimuli that induce the flight response, this inhibition quickly undergoing attenuation. Thes data do not suggest that activation of defense area, per se, contributes to the development of primary hypertension