β-Adrenoceptors in the dorsal hippocampus are involved in ethanol-induced state-dependent retrieval in mice

This study was designed to investigate the involvement of β-adrenoceptors of the dorsal hippocampus (DH) in ethanol-induced state-dependent retrieval. We used a step-down type of inhibitory avoidance (IA) task to assess retrieval in male NMRI mice. Bilateral guide cannulae were implanted in the DH. The results showed that in the animals with pre-training injections of ethanol (1g/kg, i.p.) and pre-test saline treatment memory retrieval was impaired. Pre-test injections of ethanol (0.5 and 1g/kg, i.p.) also impaired memory retrieval in the animals that received saline before training. Ethanol (1g/kg, i.p.), when injected in both time points of pre-training and pre-test, induced state-dependent retrieval. The results also revealed that intra-DH infusions of a β-adrenoceptor agonist salbutamol (0, 0.0025, 0.005, 0.01 and 0.02 μg/mouse) by itself had no significant effect, however, along with an ineffective dose of ethanol (0.25 g/kg) significantly improved memory retrieval. On the other hand, pre-test intra-DH infusions of different doses of a non-selective β-adrenoceptor antagonist propranolol (0, 0.1, 0.3 and 0.5 μg/mouse) by itself had no effect on memory retrieval. But, pre-test intra-DH infusions of the same doses of propranolol (0, 0.1, 0.3 and 0.5 μg/mouse) disrupted ethanol-induced state-dependent retrieval. Interestingly, intra-DH infusions of propranolol (0.05, 0.75 and 0.1 μg/mouse) inhibited the improving effect of salbutamol on state-dependent retrieval. In conclusion, the results support the existence of a functional involvement of β-adrenoceptors in the DH in ethanol-induced state-dependent retrieval.