Sub-chronic cold stress reduces 5-HT1A receptor responsiveness in the old but not in the young rat.
The inhibitory effect of the prototypical 5-hydroxytryptamine (5-HT)1A receptor agonist 8-hydroxy-2-(di-n-propyl amino)tetraline (8-OH-DPAT) on forskolin-stimulated adenylyl cyclase activity, has been examined as an index of the functional activity of 5-HT1A receptors in the hippocampus of young (3 months) and old (18 months) rats exposed during 24 h or 5 days to cold. In both young and old rats exposed to cold stress during 24 h, there was a reduction in the potency (EC50) and/or the maximal inhibitory effect (Emax) of 8-OH-DPAT in reducing forskolin-induced cAMP accumulation. The properties of the hippocampal 5-HT1A sites labelled by [3H]8-OH-DPAT were not affected by these stressful conditions. Moreover, while the sensitivity of 5-HT1A receptors to 8-OH-DPAT in young rats returned to control values after 5 days of cold exposure, old rats still exhibited a significant desensitization of 5-HT1A receptors as compared to naive animals. These results point out the capacity of young but not of old rats to adapt to the aversive effects of a subchronic stressor.
Manhães de Castro
R
R
Unité de Pharmacologie Neuro-Immuno-Endocrinienne de l'Institut Pasteur, Paris, France.
Bolaños-Jiménez
F
F
Seguin
L
L
Sarhan
H
H
Drieu
K
K
Fillion
G
G
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D003080:Cold Temperature; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D013312:Stress, Physiological / Q000503:physiopathology*
D011985:Receptors, Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000242:Cyclic AMP