Brain acetylcholinesterase activity in relation to induced reproductive activity in Mozambique tilapia (Oreochromis mossambicus Peters)

Teleosts inhabiting fresh water (FW) depend upon ion-absorptive ionocytes to counteract diffusive ion losses to the external environment. A Clc Cl−channel family member, Clc-2c, was identified as a conduit for basolateral Cl−transport by Na+/Cl−cotransporter 2 (Ncc2)-expressing ionocytes in stenohaline zebrafish (Danio rerio). It is unresolved whether Clc-2c/clc-2cis expressed in euryhaline species and how extrinsic and/or intrinsic factors modulate branchialclc-2cmRNA. Here, we investigated whether environmental salinity, prolactin (Prl) and osmotic conditions modulateclc-2cexpression in euryhaline Mozambique tilapia (Oreochromis mossambicus). Branchialclc-2candncc2mRNAs were enhanced in tilapia transferred from seawater (SW) to FW, whereas both mRNAs were attenuated upon transfer from FW to SW. Next, we injected hypophysectomized tilapia with ovine prolactin (oPrl) and observed a marked increase inclc-2cfrom saline-injected controls. To determine whether Prl regulatesclc-2cin a gill-autonomous fashion, we incubated gill filaments in the presence of homologous tilapia Prls (tPrl177and tPrl188). By 24 h, tPrl188stimulatedclc-2cexpression ~5-fold from controls. Finally, filaments incubated in media ranging from 280 to 450 mosmol/kg for 3 and 6 h revealed that extracellular osmolality exerts a local effect onclc-2cexpression;clc-2cwas diminished by hyperosmotic conditions (450 mosmol/kg) compared with isosmotic controls (330 mosmol/kg). Our collective results suggest that hormonal and osmotic control of branchialclc-2ccontributes to the FW adaptability of Mozambique tilapia. Moreover, we identify for the first time a regulatory link between Prl and a Clc Cl−channel in a vertebrate.

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Transitional Versus Surgical Menopause in a Rodent Model: Etiology of Ovarian Hormone Loss Impacts Memory and the Acetylcholine System

Endocrinology ◽

10.1210/en.2008-1802 ◽

2009 ◽

Vol 150 (9) ◽

pp. 4248-4259 ◽

Cited By ~ 57

Author(s):

Jazmin I. Acosta ◽

Loretta Mayer ◽

Joshua S. Talboom ◽

Candy Wing S. Tsang ◽

Constance J. Smith ◽

...

Keyword(s):

Memory Task ◽

Acetylcholinesterase Activity ◽

Rodent Model ◽

Surgical Removal ◽

Ovarian Hormone ◽

Vinylcyclohexene Diepoxide ◽

Menopausal Women ◽

Surgical Menopause ◽

Negative Effect ◽

Brain Acetylcholinesterase

Abstract Clinical research suggests that type of ovarian hormone loss at menopause influences cognition. Until recently ovariectomy (OVX) has been the primary rodent model to examine effects of ovarian hormone loss on cognition. This model limits evaluations to abrupt and complete ovarian hormone loss, modeling less than 13% of women who receive surgical menopause. The majority of women do not have their ovaries surgically removed and undergo transitional hormone loss via ovarian follicular depletion. 4-Vinylcyclohexene-diepoxide (VCD) produces gradual ovarian follicular depletion in the rodent, with hormone profiles more similar to naturally menopausal women vs. OVX. We directly compared VCD and OVX models to examine whether type of hormone loss (transitional vs. surgical) impacted cognition as assessed on a maze battery as well as the cholinergic system tested via scopolamine mnemonic challenge and brain acetylcholinesterase activity. Middle-aged rats received either sham surgery, OVX surgery, VCD, or VCD then OVX to assess effects of removal of residual ovarian output after transitional menopause and follicular depletion. VCD-induced transitional menopause impaired learning of a spatial recent memory task; surgical removal of residual ovarian hormones by OVX abolished this negative effect of transitional menopause. Furthermore, transitional menopause before OVX was better for memory than an abrupt loss of hormones via OVX only. Surgical ovarian hormone loss, regardless of menopause history, increased hippocampal acetylcholinesterase activity. Circulating gonadotropin and androstenedione levels were related to cognitive competence. Collectively, findings suggest that in the rat, initiation of transitional menopause before surgical ovary removal can benefit mnemonic function and could obviate some negative cognitive consequences of surgical menopause alone.

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