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“School of Cognitive Sciences”

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Paper   IPM / Cognitive Sciences / 11300
School of Cognitive Sciences
  Title:   Involvement of dorsal hippocampal a-adrenergic receptors in the effect of scopolamine on memory retrieval in inhibitory avoidance task
1.  Nasrin Azami
2.  Morteza Piri
3.  Shahrbano Oryan
4.  Mehrdad Jahanshahi
5.  Vahab Babapour
6.  Mohammad Reza Zarrindast
  Status:   Published
  Journal: Neurobiology of Learning and Memory
  Vol.:  93
  Year:  2010
  Pages:   455-462
  Supported by:  IPM
The present study evaluated the possible role of a-adrenergic receptors of the dorsal hippocampus on scopolamine-induced amnesia and scopolamine state-dependent memory in adult male Wistar rats. The animals were bilaterally implanted with chronic cannulae in the CA1 regions of the dorsal hippocampus, trained in a step-through type inhibitory avoidance task, and tested 24 h after training to measure step-through latency. Results indicate that post-training or pre-test intra-CA1 administration of scopolamine (1 and 2 lg/rat) dose-dependently reduced the step-through latency, showing an amnestic response. Amnesia produced by post-training scopolamine (2 lg/rat) was reversed by pre-test administration of the scopolamine that is due to a state-dependent effect. Interestingly, pre-test intra-CA1 microinjection of a1-adrenergic agonist, phenylephrine (1 and 2 lg/rat) or a2-adrenergic agonist, clonidine improved post-training scopolamine (2 lg/rat)-induced retrieval impairment. Furthermore, pre-test intra-CA1 microinjection of phenylephrine (0.25, 0.5 and 1 lg/rat) or clonidine (0.25, 0.5 and 1 lg/rat) with an ineffective dose of scopolamine (0.25 lg/rat), synergistically improved memory performance impaired by post-training scopolamine. On the other hand, pre-test injection of a1-receptors antagonist prazosin (1 and 2 lg/rat) or a2-receptors antagonist yohimbine (1 and 2 lg/rat) prevented the restoration of memory by pre-test scopolamine. It is important to note that pre-test intra-CA1 administration of the same doses of prazosin or yohimbine, alone did not affect memory retrieval. These results suggest that a1- and a2-adrenergic receptors of the dorsal hippocampal CA1 regions may play an important role in scopolamine-induced amnesia and scopolamine state-dependent memory.

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