title: Effects of ovariectomy and calcium deficiency on learning and memory of eight-arm radial maze in middle-aged female rats.
abstract: There is increasing evidence that estrogen and calcium ion are involved in learning and memory. In the present study, to examine the effect of estrogen deficiency and low-calcium diet on learning and memory, middle-aged female Wistar rats (50 weeks old) were fed either a low-calcium (0.02% Ca) or a normal-calcium (1.25% Ca) diet throughout the experiment. Rats were ovariectomized (OVX) or sham-operated (Sham). These animals were divided into four groups: 1) Sham group with normal-calcium diet [Sham-normal Ca group], 2) OVX group with normal-calcium diet [OVX-low Ca group], 3) Sham group with low-calcium diet [Sham-low Ca group], 4) OVX group with low-calcium diet [OVX-low Ca group]. Seventy-seven days after the OVX or Sham operation, the learning and memory abilities in the female rats were examined by using a radial maze task according to the method of Olton and Samuelson (regular trials) and using a delay-interposed task following regular trials. During regular trials and delay-interposed tasks, the OVX-low Ca group was inferior to all the other groups in accuracy of choice behavior. Both Sham-normal Ca and Sham-low Ca groups showed more accurate choices than the OVX-low Ca group, but were less accurate than the Sham-normal Ca group. In addition, there was no significant difference in locomotor activity between any of the groups. These results suggest that OVX or low-calcium diet may impair learning and memory, and that the combination of these factors impaired more markedly when the rats were tested in the eight-arm radial maze. These results may also imply the possibility that a woman in menopause or post-menopause suffers impairment of learning and/or memory when intakes low-calcium diet.
authors.affiliation: Department of Pharmacology, Kagoshima University Dental School, Sakuragaoka, Kagoshima 890-854, Japan. tomsato@dentb.hal.kagoshima-u.ac.jp
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Sato
authors.forename: Toyonori
authors.initials: T
authors.lastname: Teramoto
authors.forename: Koh-ichi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Ohnishi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Irifune
authors.forename: Takashige
authors.initials: T
authors.lastname: Nishikawa
mesh_terms: D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000172:deficiency / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology; D004967:Estrogens / Q000172:deficiency / Q000502:physiology*; D005260:Female; D018782:Maze Learning / Q000502:physiology*; D008568:Memory / Q000502:physiology; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004967:Estrogens; D002118:Calcium