Positive emotional arousal increases duration of memory traces: Different role of dopamine D1 receptor and β-adrenoceptor activation D. Conversi a,b, ⁎, F. Cruciani a , A. Accoto a , S. Cabib a,b a Department of Psychology, Center D. Bovet, University “Sapienza”, Rome, Italy b Fondazione Santa Lucia IRCCS, European Centre for Brain Research, Rome, Italy abstract article info Article history: Received 3 December 2013 Received in revised form 19 February 2014 Accepted 2 April 2014 Available online 13 April 2014 Keywords: Long-term memory Propranolol SCH 23390 Emotional arousal Object recognition Beta-adrenoceptors We investigated the effects of post-training administration of dopamine D1 receptor antagonist SCH 23390 and β-adrenergic receptor antagonist Propranolol on memory retention of an object sampled in a state of positive emotional arousal. Saline-treated mice trained and tested under high emotional/motivational arousal (High) showed discrimination of a novel object both 24 and 96 h post-training. Instead, mice trained and tested under low motivational arousal (Low) were unable to discriminate the novel object 96 h post-training. Both a high (2 mg/kg) and a low (1 mg/kg) dose of Propranolol reduced object discrimination in High mice tested 24 h post-training, whereas neither dose was effective in Low mice. A high dose of SCH 23390 (0.025 mg/kg) reduced discrimination of the novel object in High mice tested both 24 and 96 h post-training, whereas a low dose of the D1 antagonist (0.01 mg/kg) reduced discrimination in High mice tested 96 h post-training and abolished discrimination in Low mice tested 24 h after training. © 2014 Elsevier Inc. All rights reserved. 1. Introduction Catecholamines dopamine (DA) and norepinephrine (NE) play a major role in consolidation of lasting memory traces. Blockade or stimulation of the two major subtypes of DA receptors, D1 and D2, reduces and facilitates, respectively, memory consolidation in different tasks (Castellano et al., 1991; LaLumiere and McGaugh, 2005; LaLumiere et al., 2005; Managò et al., 2008; Moncada et al., 2011). The same holds true for manipulations of β-adrenergic receptors (Cahill et al., 1998; McGaugh, 2000; de Quervain et al., 2009; Moncada et al., 2011). Moreover, there is evidence that the two catecholamines could interact or act in concert to modulate memory consolidation under high emotional arousal (LaLumiere and McGaugh, 2005; LaLumiere et al., 2005; Moncada et al., 2011). However, if the role of dopamine receptors in regulating retention in high arousing memory tasks is widely investigated (Castellano et al., 1991; Castellano et al., 1996; Managò et al., 2008; Zarrindast et al., 2012), the modulatory influence of these receptors on consolidation of object recognition memory, a mild-arousing memory task, remains poorly understood. In a study in 2011, de Lima and coworkers show that, under certain experimental conditions, recognition memory is modulated by the dopaminergic system in a way that memory consolidation can be enhanced by D1 re- ceptor activation, but dopamine receptors are not critical for memory formation, thus neither D1 receptor blockade nor D2 receptor activation impairs memory. Furthermore, the enhancement of memory retention of arousing tasks seems to be mediated by release of norepinephrine and activation of β-adrenoceptor in several brain areas, such as basolateral complex of amygdala (McGaugh, 2000;McGaugh, 2004; McGaugh and Roozendaal, 2002). This hypothesis is supported by the evidence that systemic and in loco post-training administration of Propranolol, a β-adrenoceptor antagonist, impairs consolidation of several memory tasks, such as inhibitory avoidance and object recognition memory (Cahill et al., 2000; Dornelles et al., 2007; Roozendaal et al., 2004, 2006, 2008). More- over, several findings demonstrate that the influence of β-adrenergic receptor stimulation on memory retention of sampled object depends on the level of emotional arousal (Okuda et al., 2004; Roozendaal et al., 2006). The present experiments evaluate the effects of post-training administration of the DA D1 receptor antagonist SCH 23390 and of the β-adrenergic antagonist Propanolol in a modified one-trial version of the object recognition test (ORT) that allows to manipulate the level of emotional/motivational arousal during exposure to the sample objects (Cruciani et al., 2011). The procedure involves association of the experimental cage with a palatable food, milk chocolate (high emotional arousing experience, High), or with a piece of plastic of the same size (low emotional arousing experience, Low), in a free-feeding condition. Then, all animals are food-restricted and presented with the sample objects. The rationale for this procedure is based on several lines of evidence supporting the view that animals respond with a Pharmacology, Biochemistry and Behavior 122 (2014) 158–163 ⁎ Corresponding author at: Dipartimento di Psicologia, Università “Sapienza”, via dei Marsi 78, Rome I-00185, Italy. Tel.: +39 06 4991 7612; fax: +39 06 4991 7712. E-mail address: david.conversi@uniroma1.it (D. Conversi). http://dx.doi.org/10.1016/j.pbb.2014.04.001 0091-3057/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Pharmacology, Biochemistry and Behavior journal homepage: www.elsevier.com/locate/pharmbiochembeh