β-Adrenergic receptors in the insular cortex are differentially involved in aversive vs. incidental context memory formation

Abstract

The goal of this research was to determine the effects of b-adrenergic antagonism in the IC before or after inhibitory avoidance (IA) training or context pre-exposure in a latent inhibition protocol. Pretraining intra-IC infusion of the b-adrenergic antagonist propranolol disrupted subsequent IA retention and impaired latent inhibition of IA, but had no effect on formation of memory for an inert context (termed incidental memory). These results indicate that IC b-adrenergic receptors are necessary for memory acquisition of an aversive, but not an inconsequential, context. Nevertheless, subsequent association of a familiar and hitherto inconsequential context with an unconditioned stimulus (US) does require activation of these receptors during its initial acquisition.Substantial evidence indicates that long-term memories related to emotional experiences are particularly robust (Buchanan 2007). However, a substantial component of our memories are related to incidental stimuli, that is, stimuli that have no overt emotional relation. Recent data have implicated the insular cortex (IC) in the formation of such "incidental" memories (BermudezRattoni 2004;Miranda and Bermudez-Rattoni 2007;Miranda et al. 2008). The IC has substantial connections with the limbic system and the "reward circuit," and receives information from all sensory modalities Mufson and Mesulam 1982). Functionally, the IC has been demonstrated to play a critical role in memory performance in a variety of memory tasks that use an aversive unconditioned stimulus (US), including taste recognition memory (Bermudez-Rattoni 2004), Morris spatial water maze Gutierrez et al. 1999), and the inhibitory-avoidance (IA) task , as well as memory performance in a task with no overtly aversive stimuli, namely, object recognition (Bermudez-Rattoni et al. 2005).Though the IC has been shown to be necessary for spatial and avoidance memory formation (Bermudez-Rattoni and McGaugh 1991) and the b-adrenergic system has been shown to play a critical role in IA consolidation (Barros et al. 2001;Lalumiere et al. 2004;McGaugh 2004), the functions of b-adrenergic activity in the IC during IA acquisition, consolidation, and retrieval are unknown. Hence, the present study was designed to examine the involvement of b-adrenergic receptors in the IC during acquisition and memory consolidation of the IA task. We further investigated whether b-adrenergic receptors in the IC might be differentially involved in mediating aversive and incidental contextual memory formation, as well as their role in a latent inhibition variant of the IA task. Specifically, the latent inhibition IA paradigm involves pre-exposing animals to the IA dark compartment in the absence of a footshock and then assessing their latency to enter that same dark compartment the following day, at which time a footshock is then administered. Lubow (1989) showed that this kind of pre-exposure reduces the probability of the apparatus context being associated with a footshock applied when the animal is placed in that context...

Activation of β2-adrenoceptor enhances synaptic potentiation and behavioral memory via cAMP-PKA signaling in the medial prefrontal cortex of rats

“…b-ARs include three subtypes, b1, b2, and b3, which are all present in the nervous system. Extensive behavioral and physiological studies have demonstrated that b-AR activation facilitates long-term potentiation (LTP) (Katsuki et al 1997;Lin et al 2003;Straube et al 2003;Gelinas and Nguyen 2005;O'Dell et al 2010;Connor et al 2011) and enhances memory (Ji et al 2003;Tronel et al 2004;Lemon et al 2009;Miranda et al 2011).…”