| Part I Involvement of (β-adrenoceptors in hippocampal CA1 region in in vivo long-term potentiation and spatial learning in rats Activation of (β-adrenoceptors in area CA1 of the hippocampus facilitates in vitro long-term potentiation (LTP) in this region. However, it is unclear if in vivo LTP in area CA1 and hippocampus-dependent learning are subjected to (-adrenergic regulation. To address this question, we investigated the effects of the (-adrenergic agonist L-isoproterenol or antagonist DL-propranolol on in vivo LTP of area CA1 and spatial learning in Morris water maze. In the presence of L-isoproterenol (through local infusion into area CA1), the theta-pulse stimulation with the parameter of 10 Hz, 150 pulses/train, 1 train, a frequency weakly modifying synaptic strength, induced a robust LTP, and this effect was blocked when DL-propranolol was co-administered. By contrast, the theta-pulse stimulation with the parameter of 5 Hz, 150 pulses/train, 3 train, a frequency strongly modifying synaptic strength, induced a significantly smaller LTP when DL-propranolol was administered into area CA1. Accordingly, DL-propranolol impaired rat's spatial learning in the water maze when infused into area CA1 20min pretraining. Compared with control rats, the DL-propranolol-treated rats showed significantly slower learning in the water maze and subsequently exhibited poor memory retention at 24-hrtest. These results suggest that β-adrenoceptors in area CA1 are involved in regulating in vivo synaptic plasticity of this area and are important for spatial learning. The present study was the first work where theta-pulse-stimulation-induced LTP was recorded in area CA1 in vivo and its (-adrenergic regulation was examined, and provided the first behavioral evidence that (-adreneoceptors in area CA1 plays an important role in spatial learning.Key words:β-adrenoceptors, long-term potentiation, CA1, hippocampus, spatial learning, rat...
|
PDF Full Text Request