Regulation of conditioned responses of basolateral amygdala neurons
Section snippets
Afferent regulation of the amygdala
The amygdala is divided into a number of subregions. Two of these subregions are of particular interest to our laboratory: (1) the basolateral amygdala (BLA)—this region is comprised of principal output neurons that are glutamatergic, pyramidal-shaped neurons, and provide excitatory output to a number of rostral brain regions, including the accumbens and the prefrontal cortex (PFC); (2) the central nucleus (CeA)—this region contains primarily GABAergic neurons that project to brainstem
Prefrontal regulation of BLA responses: a functional consideration
Conceptually, we propose that the interaction of PFC afferents in the BLA may provide insight regarding how information is processed within the BLA. Thus, the presentation of a complex sensory stimulus (such as the sound of a dog barking) would be expected to evoke an emotional response by activation of the excitatory association cortical afferents to the BLA that, in turn, would suppress activity within the CeA and thereby disinhibit subcortical areas. This would include CeA projection sites
Dopamine (DA) modulation of BLA responses
The response of BLA neurons to sensory cortical stimulation was also found to be potently affected by alterations of the mesolimbic DA system. Thus, our studies show that pharmacological manipulation of DA receptors exerts multiple actions within the BLA of anesthetized rats. DA acting via D2 receptors was found to cause a potentiation of sensory cortical afferents, apparently mediated via an increase in the input resistance of the membrane (Fig. 1). As a consequence, D2 stimulation would be
Modulation of conditioned responses within the BLA
In addition to short-term modulation, the amygdala also exhibits conditioning [27], [28]. Our studies have shown that such conditioned responses can be evaluated using intracellular recording in vivo from the anesthetized rat. As reviewed above, the BLA shows activation by various stimuli. Thus, presentation of an odor to the rat's nose will evoke EPSPs in the membrane of BLA neurons. If this odor is presented repeatedly, the amplitude of the EPSPs will decrease to the point where the odor
Regulation of BLA plasticity and its relationship to schizophrenia pathophysiology
These results show that the BLA is capable of exhibiting conditioned responses on a single-neuron level, even when the animal is anesthetized. This conditioning will alter the manner in which the BLA neuron responds to normally benign stimuli, if the stimulus is paired with a potent stressor under the appropriate conditions. These conditions include stimulation by DA, as well as a lack of suppressive influence by the PFC (Fig. 3). Thus, the PFC is capable of preventing such conditioning, most
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