Abstract
Recent evidence has indicated that, when an animal is exposed to harmful stimuli, hypothalamic orexinergic neurons are activated via the amygdala and in turn tune the neuronal circuits in the spinal cord, brainstem, and an area of the cerebellum (folium-p of the flocculus) by neuromodulation. The animal would then initiate “defense reactions” composed of complex movements and associated cardiovascular responses. To investigate neuronal mechanisms of the defense reactions, Nisimaru et al. (2013) analyzed cardiovascular responses induced by an electric foot shock stimulus to a rabbit and found two major effects. One is redistribution of arterial blood flow from visceral organs to active muscles, and the other is a modest increase in blood pressure. Kainate-induced lesions of folium-p impaired these two effects. Moreover, folium-p Purkinje cells were shown to project to the parabrachial nucleus, one of the major cardiovascular centers in the brainstem. These data indicate that folium-p Purkinje cells regulate cardiovascular defense reactions via parabrachial nucleus under orexin-mediated neuromodulation. In this article, we review these data from the viewpoint that the defense reactions are expressions of “anger and anxiety”, which respectively lead to “fight and flight” behaviors. The present orexin case may provide a model of cerebellohypothalamic interactions via neuropeptides or amines of hypothalamic origin, which may underlie various types of emotion and behavior.
Highlights
The basis for assuming roles of the cerebellum in emotion is threefold: A) the presence of anatomical connections between the cerebellum and the hypothalamus [1,2,3]; B) disturbances of emotion regulation in cerebellar patients, such as “cerebellar cognitive-affective syndrome” [4,5]; and C) decreased activities in the cerebellum as revealed by brain imaging of schizophrenic patients [6,7,8]
Nisimaru et al [10] showed in rabbits that orexinergic fibers mediate the cardiovascular component of defense reactions to harmful stimuli
The cardiovascular defense reactions evoked by applying electric foot shock stimuli to a rabbit were twofold
Summary
The basis for assuming roles of the cerebellum in emotion is threefold: A) the presence of anatomical connections between the cerebellum and the hypothalamus [1,2,3]; B) disturbances of emotion regulation in cerebellar patients, such as “cerebellar cognitive-affective syndrome” [4,5]; and C) decreased activities in the cerebellum as revealed by brain imaging of schizophrenic patients [6,7,8]. Little has been known about the mechanisms by which cerebellar dysfunctions lead to impaired regulation of emotion and behavior. Orexin-containing (assumed to be orexinergic) fibers originate solely from the hypothalamus and distribute broadly in the spinal cord, brainstem, and the flocculus region of the cerebellum [9]. Nisimaru et al [10] showed in rabbits that orexinergic fibers mediate the cardiovascular component of defense reactions to harmful stimuli. Folium-p Purkinje cells may regulate cardiovascular defense reactions via parabrachial nucleus under orexin-mediated neuromodulation. We review and interpret Nisimaru et al.’s [10] observations from the viewpoint that the cardiovascular defense reactions are part of the expressions of anger and anxiety against harmful stimuli, which would respectively lead to fight and flight behaviors. Extending the present case of cerebellohypothalamic interactions via orexins, we may hypothesize that there are a number of neuropeptides or amines of hypothalamic origin, which form a selection mechanism for different types of emotion and behavior
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