Basolateral amygdala glutamatergic activation enhances taste aversion through NMDA receptor activation in the insular cortex

Abstract

In conditioned taste aversion (CTA), a subject learns to associate a novel taste with visceral malaise. Brainstem, limbic and neocortical structures have been implicated in CTA memory formation. Nevertheless, the role of interactions between forebrain structures during these processes is still unknown. The present experiment was aimed at investigating the possible interaction between the basolateral nucleus of the amygdala (BLA) and the insular cortex (IC) during CTA memory formation. Injection of a low dose of lithium chloride (30 mg/kg, i.p.) 30 min after novel taste consumption (saccharin 0.1%) induces a weak CTA. Unilateral BLA injection of glutamate (2 microg in 0.5 microL) just before low lithium induces a stronger CTA. Unilateral injection of an N-methyl-d-aspartate (NMDA) receptor antagonist (AP5, 5 microg in 0.5 microL) in IC has no effect. However, AP5 treatment in IC at the same time or 1 h after the ipsilateral BLA injection reverses the glutamate-induced CTA enhancement. Injection of AP5 in IC 3 h after BLA injection does not interfere with the glutamate effect. Moreover, the CTA-enhancing effect of glutamate was also blocked by contralateral IC injection of AP5 at the same time. These results provide strong evidence that NMDA receptor activation in the IC is essential to enable CTA enhancement induced by glutamate infusion in the BLA during a limited time period that extends to 1 but not to 3 hours. These findings indicate that BLA-IC interactions regulate the strength of CTA. The bilateral nature of these amygdalo-cortical interactions is discussed.

Acute suppression, but not chronic genetic deficiency, of c- fos gene expression impairs long-term memory in aversive taste learning

“…Lamprecht et al (35) also showed that inhibition of cAMP response element-binding protein (CREB), one of the regulatory transcriptional factors for c-fos gene expression, in the AMY with in vivo AS-ODN technology disrupted the retention, but not the acquisition, of CTA. In line with these results, Bermudez-Rattoni and colleagues (36,37) have suggested that positive interaction between the basolateral AMY-IC enhances the strength of long-term CTA memory.…”

Glutamate Microinjected in the Posterodorsal Medial Amygdala Induces Subtle Increase in the Consumption of a Three‐Choice Macronutrient Self‐Selection Diet in Male Rats

“…The ''hit rate'' for MePD microinjections reflects the rigorous including criteria and the small size of this brain subnucleus (see also King et al, 1999;Grundmann et al, 2005). The doses of glutamate were adapted from previous reports, that is, the lowest dose of glutamate is close to the physiological values obtained by brain microdialysis in various amygdaloid nuclei and the highest dose is a pharmacological one (Fillenz, 1995;Kaura et al, 1995;Ferreira et al, 2005). Microinjections in the MePD were done while gently restraining the rat, lasted for 1 min and the needle remained inside the cannula for an additional minute to avoid reflux (de Castilhos et al, 2006).…”

The Way an Odor Is Experienced during Aversive Conditioning Determines the Extent of the Network Recruited during Retrieval: A Multisite Electrophysiological Study in Rats

“…An animal is classically judged as aversive on the basis of its decrease of consumption measured during the entire session (Ferreira et al, 2005;Chapuis et al, 2007); however, our experimental design allowed us to distinguish, within aversive groups, two behavioral responses across the different trials of the same test session. As illustrated by the examples of licking pattern (Fig.…”