Role of Central Amygdala Neuronal Ensembles in Incubation of Nicotine Craving

Abstract

The craving response to smoking-associated cues in humans or to intravenous nicotine-associated cues in adult rats progressively increases or incubates after withdrawal. Here, we further characterized incubation of nicotine craving in the rat model by determining whether this incubation is observed after adolescent-onset nicotine self-administration. We also used the neuronal activity marker Fos and the Daun02 chemogenetic inactivation procedure to identify cue-activated neuronal ensembles that mediate incubation of nicotine craving. We trained adolescent and adult male rats to self-administer nicotine (2 h/d for 12 d) and assessed cue-induced nicotine seeking in extinction tests (1 h) after 1, 7, 14, or 28 withdrawal days. In both adult and adolescent rats, nicotine seeking in the relapse tests followed an inverted U-shaped curve, with maximal responding on withdrawal day 14. Independent of the withdrawal day, nicotine seeking in the relapse tests was higher in adult than in adolescent rats. Analysis of Fos expression in different brain areas of adolescent and adult rats on withdrawal days 1 and 14 showed time-dependent increases in the number of Fos-positive neurons in central and basolateral amygdala, orbitofrontal cortex, ventral and dorsal medial prefrontal cortex, and nucleus accumbens core and shell. In adult Fos-lacZ transgenic rats, selective inactivation of nicotine-cue-activated Fos neurons in central amygdala, but not orbitofrontal cortex, decreased "incubated" nicotine seeking on withdrawal day 14. Our results demonstrate that incubation of nicotine craving occurs after adolescent-onset nicotine self-administration and that neuronal ensembles in central amygdala play a critical role in this incubation.

The Anterior Insular Cortex→Central Amygdala Glutamatergic Pathway Is Critical to Relapse after Contingency Management

“…This pattern of results is consistent with previous results from incubation of craving studies on the role of CeA but not BLA in ‘incubated’ cocaine, methamphetamine, or nicotine seeking after forced abstinence (Funk et al, 2016; Li et al, 2015b; Lu et al, 2005b; Lu et al, 2007; Xi et al, 2013). The present and previous results indicate that CeA activity plays a critical role in drug seeking after prolonged abstinence, independent of the method used to achieve abstinence (forced or voluntary).…”

“…We focused on the CeA, because we and others previously found that neuronal activity in this brain region is critical for the time-dependent increases in cocaine, methamphetamine, and nicotine seeking after forced abstinence (incubation of drug craving) (Funk et al, 2016; Li et al, 2015b; Lu et al, 2005b; Xi et al, 2013). Additionally, pharmacological inhibition of CeA neuronal activity decreases reinstatement of cocaine seeking after extinction (Alleweireldt et al, 2006; Kruzich and See, 2001).…”

Incubation of Methamphetamine but not Heroin Craving After Voluntary Abstinence in Male and Female Rats

“…Based on their clinical observations, Gawin and Kleber (1986) proposed that cueinduced cocaine craving increases during early abstinence and remains elevated for extended time periods. An analogous phenomenon termed 'incubation of drug craving' has been observed in rats and mice trained to self-administer cocaine (Grimm et al, 2001;Mead et al, 2007;Neisewander et al, 2000) and rats trained to self-administer alcohol (Bienkowski et al, 2004), nicotine (Abdolahi et al, 2010;Funk et al, 2016), heroin (Fanous et al, 2012;Shalev et al, 2001), and methamphetamine (Li et al, 2015;Shepard et al, 2004). In animal models, incubation of drug craving refers to the time-dependent increase in drug seeking during forced abstinence (Pickens et al, 2011;Wolf, 2016).…”

Corticostriatal plasticity, neuronal ensembles, and regulation of drug-seeking behavior

“…Furthermore, ensembles in the ventral medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) were shown to encode the context-induced operant responding for heroin during relapse and after extended abstinence, respectively (Bossert et al, 2011, Fanous et al, 2012). Additionally, ensembles in the dorsal striatum were linked to voluntary abstinence from methamphetamine taking (Caprioli et al, 2017), ensembles in the central amygdala to craving alcohol and nicotine during abstinence (Funk et al, 2016, de Guglielmo et al, 2016), and ventral mPFC ensembles were found to suppress ethanol seeking and drive or inhibit seeking of natural rewards depending on environmental contingencies (Pfarr et al, 2015, Suto et al, 2016, Warren et al, 2016). Importantly, all these studies report a very small number of activated neurons in a given brain region (e.g., <5%), indicating that highly specific addictive behaviors are regulated by small ensembles of neurons throughout the brain.…”