Galanin and learning.
A number of studies indicate that galanin (GAL) is a potent modulator of basal acetylcholine release in the rat forebrain e.g. in the cholinergic neurons of the septo-hippocampal projections. Thus, GAL perfused through the microdialysis probe decreased basal acetylcholine release in the ventral hippocampus, while it enhanced acetylcholine release in the dorsal hippocampus. This finding indicates that GAL may act via different mechanisms within the subsystems of the hippocampus. This hypothesis has received support from studies using the Morris swim maze, a learning task dependent on hippocampal mechanisms. GAL (3 nmol/rat) infused into the ventral hippocampus impaired spatial learning acquisition, while it tended to facilitate when injected into the dorsal hippocampus. However, the effects of GAL on acetylcholine release and on spatial learning, which are due to activation of GAL-receptors, appear to be indirectly mediated possibly via noradrenaline transmission. GAL is also a potent inhibitor of mesencephalic 5-HT neurotransmission in vivo. These findings are discussed in relation to the role of acetylcholine and serotonin in cognition.
Ogren
S O
SO
Division of Cellular and Molecular Neurochemistry, Department of Neuroscience, Karolinska Institute, SE-171 77, Stockholm, Sweden. sven.ove.ogren@neuro.ki.se
Schött
P A
PA
Kehr
J
J
Misane
I
I
Razani
H
H
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D019004:Galanin / Q000494:pharmacology* / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D044263:Receptors, Serotonin, 5-HT1; D012686:Septal Nuclei / Q000187:drug effects / Q000502:physiology
D011976:Receptors, Muscarinic; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D019004:Galanin; D000109:Acetylcholine