Effect of administration of an analog of LHRH on appetitive learning in young and middle-aged female rats.
Hypothalamic luteinizing hormone-releasing hormone (LH-RH) had been reported to induce changes in defensive learning. In middle age, females exhibit a decline in their reproductive axis. Several studies in rodents suggested that hypothalamic LHRH function deteriorated in middle-aged females. Our experiments compare T-maze learning in young and middle-aged female rats and study the effect of administration of an analog of LHRH, D-Trp6-LHRH. The ovarian action of the analog was studied and a gonadectomized control group was added. No differences were observed between young and middle-aged females in acquisition, retention, and reversal of a simple discrimination in the T-maze. However, after removal of motor and spatial cues acquisition of the discrimination on visual cues was impaired in middle-aged females compared to young mature ones. Administration of D-Trp6-LHRH enhanced performance during the visual discrimination in younger females and had no action in middle-aged ones, whereas it inhibited ovary function in both groups. Ovariectomy had no effect. These results suggest a direct effect of the analog of LHRH on the CNS and show that this peptide fails to counteract the deleterious effect of age on performance.
Nauton
P
P
Laboratoire de Psychophysiologie et Neuroendocrinologie, Université Blaise Pascal, Aubière, France.
Giry
N
N
Bruhat
M A
MA
Alliot
J
J
D000375:Aging / Q000523:psychology*; D000818:Animals; D001070:Appetitive Behavior / Q000187:drug effects*; D003463:Cues; D004193:Discrimination Learning / Q000187:drug effects*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008568:Memory / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010053:Ovary / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012193:Reversal Learning / Q000187:drug effects; D017329:Triptorelin Pamoate / Q000494:pharmacology*
D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone