Effects of ageing and long-term operant conditioning on behavior and presynaptic cholinergic and dopaminergic neuronal mechanisms in rats.
Presynaptic events in the brain, such as neurotransmitter synthesis and release, may change during ageing or by performance of an operant behavior. Therefore, we measured the acetylcholine synthesis and release, and the dopamine release in brain tissue from different groups of rats. Male Sprague-Dawley rats, 4-5 or 16-17 months old, were housed individually under identical conditions; one group of the older rats was maintained under an operant conflict procedure for 8 months. Striatal and cerebral cortex slices were preincubated with [3H]dopamine and [3H]choline, respectively, superfused and stimulated electrically. Different Ca++ concentrations were used and, in [3H]dopamine experiments, 0.1 mumol/l of apomorphine was added. Hippocampal slices were incubated with [3H]choline, and 3H-uptake and [3H]acetylcholine synthesis were measured. Gross behavior was not different between the groups as regards duration of exploration, defecation rate or spontaneous motility. Uptake of [3H]choline and synthesis of [3H]acetylcholine tended to be lower in the aged rats but did not differ significantly in the groups. The [3H]dopamine release was significantly reduced by 20% in aged rats as compared to young or aged, trained rats. The effect of changes in Ca++ concentrations and the response to apomorphine on the release of [3H]dopamine were similar in all groups, indicating a lack of age-related changes of the N-type Ca++ channels and presynaptic D-2 receptors. Thus, ageing coincided with an impaired striatal dopamine release which was prevented by the operant conditioning.
Reimann
W
W
Gödecke Research Institute, Freiburg, Germany.
Bartoszyk
G D
GD
Köllhofer
U
U
Schneider
F
F
Schoenherr
U
U
D000109:Acetylcholine / Q000096:biosynthesis / Q000378:metabolism*; D000375:Aging / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002794:Choline / Q000378:metabolism; D003216:Conditioning, Operant / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D002794:Choline; D000109:Acetylcholine; D002118:Calcium; D004298:Dopamine