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Facilitatory effect of estrogen on axodendritic spine formation in the hypothalamic arcuate nucleus of adult female rats
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Hypothahmes
FACILrIATORY E F F E C T OF ESTROGEN ON AXODENDRITIC SPINE FORMATION IN THE HYIt3OTHALAMIC ARCUATI~ NUCLEUS OF ADULT FEMALE RATS. A I ~ MATSUMOTO* and YASUMASA ARAI. Dept. A n a t . , Jmltendo Univ. Sch. Meal., Hongo, Tokyo 113. The h y p o t h a L ~ c a r c u a t e nucleus (ARCN) was examined u l t r a s t r u c t u r a l l y ? weeks af t er the complete deafferentation of the m e d i a l b a s a l hypothalamus (MBH) in o v a r i ectom.zed adult female r a t s . Axodendritic shaft (SHS) and spine ~synapses (SPS) w e r e counted ~n a field of 1 8 , 0 0 0 :Jm 2 in the middle p a r t of the ARC~ ~ each brain. In the o v a r i e c t c m i z e d MBH-island r a t s , the mean n u m b e r s of SHS (714 + o~) and SPS (138 ~ 9) w e r e significantly s m a l l e r than those of the intact controls (SHS: 1580 + 85, SPS: 178 + 20). When the o v a r i e c t o m i z e d MBH-island r a t s w e r e t r e a t e d with e s t r a d i o l benzoate {~,~, 2:4g/day) for 3 weeks a f t e r the brain s u r g e r y , the m e a n n u m b e r s of SHS (1214 + 66) ~nd SPS (315 +_29) w e r e significantly l a r g e r than those of the ovariecSomized MBHislan~ r a t s . The SHS value was ~.lmost c o m p a r a b l e to that of the intact c o n t r o l s . As for SPS~ the mean n u m b e r was apprc d m a t e l y twice that of the intact controls. In t h e s e EB-trea,*,ed, ovariectom).zed MBH-island r a t s , multiple s y n a p s e s (spine-shaft and s p i n e spine syn~pses) w e r e frequent!y observed. In the o v a r i e c t o m i z e d ~emales without brain s u r g e r y , h,~wever, e s t r o g e n failed to i n c r e ~ s e the n u m b e r s of SHS, SPS, a~d multiple synapses~ ~hich w e r e a l m o s t c o m p a r a b l e to tho~e of the intact, ovariectomized, or E B t r e a t e d ovarie,~,tomized c o n t r o l s . T h e s e resuL%s suggest that e s t r o g e n has a facilitatory effect on ~uxodendritic synapse formation in the deafferented ARCN, p r e s u m a b l y to stimulate not only the axonal s p r o u t ing but a l s e the ~.~odendritic spine formation of the intact ARC n e u r o n s .
Xl@
Hypothahmes
FACILrIATORY E F F E C T OF ESTROGEN ON AXODENDRITIC SPINE FORMATION IN THE HYIt3OTHALAMIC ARCUATI~ NUCLEUS OF ADULT FEMALE RATS. A I ~ MATSUMOTO* and YASUMASA ARAI. Dept. A n a t . , Jmltendo Univ. Sch. Meal., Hongo, Tokyo 113. The h y p o t h a L ~ c a r c u a t e nucleus (ARCN) was examined u l t r a s t r u c t u r a l l y ? weeks af t er the complete deafferentation of the m e d i a l b a s a l hypothalamus (MBH) in o v a r i ectom.zed adult female r a t s . Axodendritic shaft (SHS) and spine ~synapses (SPS) w e r e counted ~n a field of 1 8 , 0 0 0 :Jm 2 in the middle p a r t of the ARC~ ~ each brain. In the o v a r i e c t c m i z e d MBH-island r a t s , the mean n u m b e r s of SHS (714 + o~) and SPS (138 ~ 9) w e r e significantly s m a l l e r than those of the intact controls (SHS: 1580 + 85, SPS: 178 + 20). When the o v a r i e c t o m i z e d MBH-island r a t s w e r e t r e a t e d with e s t r a d i o l benzoate {~,~, 2:4g/day) for 3 weeks a f t e r the brain s u r g e r y , the m e a n n u m b e r s of SHS (1214 + 66) ~nd SPS (315 +_29) w e r e significantly l a r g e r than those of the ovariecSomized MBHislan~ r a t s . The SHS value was ~.lmost c o m p a r a b l e to that of the intact c o n t r o l s . As for SPS~ the mean n u m b e r was apprc d m a t e l y twice that of the intact controls. In t h e s e EB-trea,*,ed, ovariectom).zed MBH-island r a t s , multiple s y n a p s e s (spine-shaft and s p i n e spine syn~pses) w e r e frequent!y observed. In the o v a r i e c t o m i z e d ~emales without brain s u r g e r y , h,~wever, e s t r o g e n failed to i n c r e ~ s e the n u m b e r s of SHS, SPS, a~d multiple synapses~ ~hich w e r e a l m o s t c o m p a r a b l e to tho~e of the intact, ovariectomized, or E B t r e a t e d ovarie,~,tomized c o n t r o l s . T h e s e resuL%s suggest that e s t r o g e n has a facilitatory effect on ~uxodendritic synapse formation in the deafferented ARCN, p r e s u m a b l y to stimulate not only the axonal s p r o u t ing but a l s e the ~.~odendritic spine formation of the intact ARC n e u r o n s .