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Impact of 192 IgG-saporin medial septum lesions on working memory

Pizzo DP, Samadzadeh L, Thal LJ, Frielingsdorf H (2004) Impact of 192 IgG-saporin medial septum lesions on working memory. Neuroscience 2004 Abstracts 436.1. Society for Neuroscience, San Diego, CA.

Summary: It is generally believed that cholinergic input to the hippocampus (hpc) is involved in learning and memory. The objective of the present study was to clarify whether working memory as assessed by the Morris water maze (mwm) is impaired by selective lesions of the cholinergic cells in the medial septum in adult male rats using 75 ng192IgG-saporin per side. Two weeks post-lesion, naive and lesioned rats were trained in the mwm task focusing on working memory, which was tested using a new platform location every day. The difference (improvement) in latency between trial 1 and 2 was used as an index of working memory function. Nine different platform locations were tested. The locations yielding the highest group difference were retested, with increasing intertrial intervals (ITI) from 30 min to 24 h between the 1st and 2nd trial. In a majority of the trial blocks there was a trend suggesting that lesioned rats had impaired working memory, however there was no consistent significant difference between groups in any of the tasks. To potentially further separate the groups rats were then infused with nerve growth factor (NGF; 5 µg/day), or vehicle into the ventricular system. After 17 days of infusion working memory was retested, however NGF treatment did not affect performance. The lesions were complete as measured by loss of choline acetyltransferase activity (ChAT) to less than 10% of levels of the naive, vehicle treated rats. NGF infusion increased hpc ChAT activity in naive but not in lesioned rats. In conclusion, selectively reducing ChAT activity by more than 90% in the hpc is not sufficient to significantly impair working memory as assessed by the mwm. We cannot exclude that a more sensitive working memory task would reveal a deficit in the lesioned animals, however it is also possible that intact septohippocampal cholinergic projections are not crucial for working memory function.

Related Products: 192-IgG-SAP (Cat. #IT-01)

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