Basal Forebrain Cholinergic-induced Activation of Cholecystokinin Inhibitory Neurons in the Basolateral Amygdala

The basolateral amygdala (BLA) receives dense projections from cholinergic neurons of the basal forebrain. Acetylcholine can contributes to amygdala-dependent behaviors: formation and extinction of fear memory and appetitive instrumental learning. However, the cholinergic mechanism at the circuit level has not been defined yet. We demonstrated that cholinergic-induced di-synaptic inhibition of BLA pyramidal neurons exhibits a retrograde form of short-term synaptic inhibition, depolarization-induced suppression of inhibition (DSI). Activation of nicotinic receptors was sufficient to evoke action potentials in cholecystokinin (CCK)-positive inhibitory neurons, which strongly inhibit pyramidal neurons through their perisomatic synapses. Our cell type-specific monosynaptic retrograde tracing also revealed that CCK neurons are innervated by basal forebrain cholinergic neurons. Therefore, our data indicated that CCK inhibitory neurons mediate the cholinergic-induced di-synaptic inhibition of BLA pyramidal neurons.

Involvement of Neuropeptide Orexin B in Basolateral Amygdala Mediated Consummatory Behaviour in Male Wistar Albino Rats.

The basolateral amygdala has been implicated in the regulation of food intake besides the hypothalamic centres. In the present study, we hypothesized that the Orexin B, a polypeptide identified in the lateral hypothalamic region, may be involved in the modification of the functions the of amygdaloid centres. We therefore studied the effect of infusion of Orexin B and its antagonist (TCS-OX2-29) into Basolateral amygdala to study the feeding behaviour. Materials and methods: Adult male Wistar albino rats were selected and grouped into control, sham operated control and experimental groups (n=6 each) Orexin was infused in two doses (3 nmol/μl, 30 nmol/ μl) and TCS-OX2-29(10 μg/μl) was infused in another group. Sequential Food intake and water intake were measured at 1, 2, 4, 6, 12 hours and intake for the day was also recorded in all groups and the results (mean±SEM) were statistically analyzed by Kruskal Wali’s test and p<0.05 was considered significant. Results: The food intake and water intake were significantly increased (p<0.01) in the high dose group though the increase in the low dose treated animals was less. Injection of Orexin B antagonist decreased the food and water intake significantly. Discussion and conclusion: The results suggest that Orexin plays a role in the modulation of feeding behaviour. In the lower doses it did not show significant effect. At higher doses, the effect was marked. The role of orexin in ingestive behaviour is further confirmed by the action of antagonist infusion, which resulted decrease in the feeding activities.

Role of the amygdala in the reinforcement omission effect

The reinforcement omission effect (ROE) has been attributed to both motivational and attentional consequences of surprising reinforcement omission. Recent evidence suggests that the basolateral complex of the amygdala is involved in motivational components related to reinforcement value, whereas the central nucleus of the amygdala is involved in the processing of the attentional consequences of surprise. This study was designed to verify whether the mechanisms involved in the ROE depend on the integrity of either the basolateral amygdala complex or central nucleus of the amygdala. The ROE was evaluated in rats with lesions of either the central nucleus or basolateral complex of the amygdala and trained on a fixed-interval schedule procedure (Experiment 1) and fixed-interval with limited hold signaled schedule procedure (Experiment 2). The results of Experiment 1 showed that sham-operated rats and rats with lesions of either the central nucleus or basolateral area displayed the ROE. In contrast, in Experiment 2, subjects with lesions of the central nucleus or basolateral complex of the amygdala exhibited a smaller ROE compared with sham-operated subjects. Thus, the effects of selective lesions of amygdala subregions on the ROE in rats depended on the training procedure. Furthermore, the absence of differences between the lesioned groups in either experiment did not allow the dissociation of attentional or motivational components of the ROE with functions of specific areas of the amygdala. Thus, results did not show a functional double-dissociation between the central nucleus and basolateral area in the ROE.

Immunohistochemical study of parvalbumin-containing neurons in the mammalian basolateral amygdala / 대한해부학회지

The calcium-binding protein parvalbumin (PV) was localized in the basolateral amygdala of the rat, cat, dog and monkey using immunohistochemical techniques. In all species, neuronal cell bodies and fibers that are immunoreactive to PV were observed in the basolateral amygdala. In most of the amygdala, PV-immunoreactive cells had the appearance of aspiny local circuit neurons. Based primarily on the shape of the soma, PV-immunoreactive aspiny neurons were divided into three main types. Type 1 cells had a spherical soma and more than 3 dendrites, type 2 cells had angular and multipolar somata of variable sizes, and type 3 cells had fusiform somata and dendrites emanated from the opposite poles of somata. PV-immunoreactive varicose fibers formed basket-like plexi around unstained neurons, which suggests that PV is located in GABAergic basket cells, respectively. PV-immunoreactivities in the mammalian basolateral amygdala were morphologically similar, rather than different in all species.