Intraseptal muscarinic ligands and galanin: influence on hippocampal acetylcholine and cognition
Section snippets
Animals
Male Sprague–Dawley rats (ALAB or B&K, Sollentuna, Sweden), weighing 240–350 g or 340–410 g at the time of the experiment were used for all of the following experiments. The rats were housed in groups of three or four in Type IV Makrolon cages in a colony room under standardized conditions; 12-h light/dark cycle (lights on at 06:00 a.m.), temperature 19±0.5 °C (40–50% relative humidity) with food pellets (Lactamin AB, Kimstad, Sweden) and water available ad libitum. The cages and bedding
Histology
The location of each cannula tip was determined in all animals based on light microscopic examination of Thionin-stained coronal brain sections. Animals which had their infusion sites outside the boundary of the medial septal area (AP-coordinates AP +1.00 mm to +0.20 mm; see Paxinos and Watson, 1986) were excluded from the statistical analysis. Similarly, animals with their infusion site in the diagonal band of Broca, either the vertical or horizontal limb, were also excluded. The animals
Discussion
The main findings of the present studies are 1) blockade of septal muscarinic transmission by scopolamine increases hippocampal ACh release suggesting that muscarinic (cholinergic) transmission within MS/dBB exerts an inhibitory tone on SH cholinergic neurons. 2) Stimulation of septal muscarinic receptors by carbachol activates the SH cholinergic projection evidenced by increased hippocampal ACh release. 3) Although both scopolamine and carbachol produce an increase in hippocampal ACh release,
Acknowledgements
This study was supported by the Swedish Society for Medical Research, the Swedish MRC (K99-14X-11588), Alzheimerfonden, Stiftelsen Gamla Tjänarinnor and Funds of the Karolinska Institutet. The authors acknowledge the skilful technical assistance of Ms Paula Mannström and Mrs. Marjan Pontén and we thank Dr. Oliver Stiedl for helpful comments on the manuscript.
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