Positive emotional arousal increases duration of memory traces: Different role of dopamine D1 receptor and β-adrenoceptor activation

• Positive emotional arousal was induced in mice during object recognition training.
• Propranolol or SCH 23390 was injected i.p. at 0 or 120 min post-training.
• Propranolol impairs 24 h retention in high but not low arousing condition.
• SCH 23390 impairs 24 and 96 h retention both in low and high arousing conditions.
• Both Propranolol and SCH 23390 were ineffective if injected 120 min post-training.

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.