Post-retrieval disruption of a cocaine conditioned place preference by systemic and intrabasolateral amygdala β2- and α1-adrenergic antagonists

Previous work has demonstrated post-retrieval impairment in associative learning paradigms, including those mediated by drugs of abuse, using nonspecific beta-adrenergic receptor (beta-AR) antagonists. Remarkably little is known about the role of the specific beta-AR subtypes, or other adrenergic receptors, in these effects. The current study examined the effects of beta(1) and beta(2), as well as alpha(1)-adrenergic receptor antagonism following retrieval of a cocaine conditioned place preference (CPP). We found that rats administered the beta(2) antagonist ICI 118,551 (8 mg/kg intraperitoneal [IP]) or the alpha(1) antagonist prazosin (1 mg/kg IP) following a drug-free test for CPP showed attenuated preference during a subsequent test, while the beta(1) antagonist betaxolol (5 or 10 mg/kg IP) and a lower dose of prazosin (0.3 mg/kg IP) had no effect. Furthermore, post-test microinfusion of ICI 118,551 (6 nmol/side) or prazosin (0.5 nmol/side) into the basolateral amygdala (BLA) also impaired a subsequent preference. Systemic or intra-BLA ICI 118,551 or prazosin administered to rats in their home cages, in the absence of a preference test, had no effect on CPP 24 h later. ICI 118,551 also attenuated the FOS response in the BLA induced by the CPP test. These results are the first to demonstrate a role for alpha(1)- and beta(2)-specific adrenergic mechanisms in post-retrieval memory processes. These systemic and site-specific injections, as well as the FOS immunohistochemical analyses, implicate the importance of specific noradrenergic signaling mechanisms within the BLA in post-retrieval plasticity.