Serotonin pharmacodynamics in hypothalamic tissues from young and old female rats.
The purpose of this study was to determine the effects of aging on serotonin (5-HT) pharmacodynamics in rostral hypothalamic tissue of female rats. Monoamine oxidase (MAO) activity was greater in old (19 months old) than in young (3 months old) animals. This difference resulted from a higher Vmax for hypothalamic MAO from old rats, whereas Km's were comparable in both age groups. These enzymatic changes were accompanied by altered uptake and release of [3H]5-HT. Although [3H]5-HT uptake was not different at equilibrium between groups, the equilibrium state was achieved more slowly by hypothalamic tissue from old rats. Basal and potassium-stimulated efflux of [3H]5-HT was significantly greater in old rats compared with young ones and these differences remained during multiple depolarizations. The findings of this study suggest that synaptic levels of hypothalamic 5-HT increase with age. Since pharmacological simulation of this condition in young rats produces physiologic dysfunction, the spontaneous changes that occur in hypothalamic 5-HT pharmacodynamics during aging have the potential to promote senescence.
Navarro
H A
HA
Department of Anatomy, University of Kentucky, Lexington 40536.
Aloyo
V J
VJ
Rush
M E
ME
Walker
R F
RF
D000375:Aging / Q000378:metabolism*; D000818:Animals; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007034:Hypothalamus, Posterior / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008995:Monoamine Oxidase / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012701:Serotonin / Q000378:metabolism / Q000493:pharmacokinetics*
D012701:Serotonin; D008995:Monoamine Oxidase; D011188:Potassium