Aging alters norepinephrine release in the medial preoptic area in response to steroid priming in ovariectomized rats

MohanKumar, Sheba M.J.; MohanKumar, P.S.

doi:10.1016/j.brainres.2004.06.040

Cited by 22 publications

(11 citation statements)

References 25 publications

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“…This increase occurred before the increase in LH levels in these animals corroborating well with earlier studies [24, 29]. We have also reported that treatment with IL-1β suppresses NE release specifically in the MPA and this is accompanied by a blockade of the LH surge [30, 31]. In the present study, we have performed a more comprehensive analysis of GnRH-rich brain areas such as the DBB, Arc, SCN and the OVLT that have been implicated in LH regulation [7–9].…”

Section: Discussionsupporting

confidence: 91%

Interleukin-1 beta simultaneously affects the stress and reproductive axes by modulating norepinephrine levels in different brain areas

Sirivelu

MohanKumar

2012

Life Sciences

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AIMS Interleukin-1β (IL-1β) is a cytokine that is known to activate the stress axis and suppress the reproductive axis. Different brain areas are involved in the regulation of these two axes. However, they are both under the stimulatory control of the catecholamine, norepinephrine (NE). Here, we hypothesized that IL-1β differentially affects these two axes by modulating NE levels in specific brain regions. METHODS Female Sprague-Dawley rats in proestrus were injected intraperitoneally with either PBS-1.0% BSA (control) or 5 µg of IL-1β at 1 pm. Groups of rats were sacrificed at 1, 3, and 5 pm and their brains were collected. Brain areas associated with reproduction as well as areas associated with stress axis activity were isolated and analyzed for NE concentrations using HPLC-EC. Trunk blood was analyzed for IL-1β, corticosterone and luteinizing hormone levels. KEY FINDINGS As a general trend, treatment with IL-1β significantly decreased NE levels (p<0.05) in the areas controlling reproductive functions when compared to the control group. In contrast, NE levels increased significantly (p<0.05) in the stress associated areas. LH levels were markedly decreased with IL-1β treatment while corticosterone levels increased dramatically. SIGNIFICANCE The ability of IL-1β to produce differential effects on the stress and reproductive axis could be explained by modulation of NE levels in specific brain areas that are associated with these functions. This differential regulation of NE may be an adaptive phenomenon in response to a systemic immune challenge.

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Section: Discussionsupporting

confidence: 91%

Interleukin-1 beta simultaneously affects the stress and reproductive axes by modulating norepinephrine levels in different brain areas

Sirivelu

MohanKumar

2012

Life Sciences

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“…Therefore, our findings do not imply that Glu and GABA are the only possible neurotransmitter systems involved in LH surge failure. Of note, age-related decreases in hypothalamic norepinephrine are associated with LH surge abnormalities in middle-aged rats [8, 68, 75, 76]. Because GABA A agonists can attenuate norepinenphrine-induced LH release [37, 42] and bicuculline treatment can increase the sensitivity to norepinenphrine [77], it is quite possible that bicuculline treatment also modulates the noradrenergic system.…”

Section: Discussionmentioning

confidence: 99%

Restoration of the Luteinizing Hormone Surge in Middle-Aged Female Rats by Altering the Balance of GABA and Glutamate Transmission in the Medial Preoptic Area1

Neal‐Perry

Zeevalk

Shu

et al. 2008

Biology of Reproduction

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Hypothalamic glutamate and GABA neurotransmission are involved in the ovarian hormone-induced GnRH-LH surge in rodents. We previously reported that middle-aged rats have significantly less glutamate release in the medial preoptic area than young rats on the day of the LH surge. The present study tested the hypothesis that the delayed and attenuated LH surge in ovariohysterectomized, middle-aged rats primed with ovarian steroids results from reduced hypothalamic glutamate and increased GABAA neurotransmission. Microdialysis results show that middle-aged rats with attenuated LH surges had reduced extracellular glutamate and increased extracellular GABA levels in the medial preoptic area compared to young rats. Blocking GABAA receptors with bicuculline or inhibiting synaptic glutamate reuptake with L-trans-pyrrolidine-2,4-dicarboxylic acid increased extracellular Glu in the medial preoptic area and partially restored LH surge amplitude in middle-aged rats without altering LH surge onset. Complete recovery of LH surge amplitude was observed in middle-aged rats treated with the combination of bicuculline and L-trans-pyrrolidine-2,4-dicarboxylic acid. This treatment also restored the extracellular glutamate:GABA ratio in the medial preoptic area of middle-aged rats to the level of young rats. Immunoblot analysis revealed that estradiol and progesterone treatment reduced SLC32A1(formerly known as vesicular GABA transporter) levels and increased SLC17A6 (formerly known as vesicular glutamate transporter 2) levels in the anterior hypothalamus of ovariohysterectomized young but not middle-aged rats. These data suggest that both reduced availability of glutamate and increased activation of GABAA receptors under estrogen positive feedback conditions contribute to the age-related delay in onset and attenuated amplitude of the LH surge.

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“…Other modulators of GnRH release also change in middle-aged rats exhibiting delayed and attenuated LH surges. Examples include norepinephrine,54,55 neuropeptide Y,56 and VIP 24. Interestingly GABA modulates norepiniephrine57 and glutamate28 release; hence, increased hypothalamic GABA release may restrain excitatory signals transmitted by these neurotransmitters to GnRH neurons.…”

Section: Rodentsmentioning

confidence: 99%

The neuroendocrine physiology of female reproductive aging: An update

2010

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The transition into menopause is a complex process that affects fertility and increases the risk for a number of health problems in aging women that include, but are not limited to osteoporosis, heart disease, diabetes mellitus and cognitive dysfunction. Improved nutrition and enhanced access to medical care have increased the average lifespan for women in developed countries, and many will spend more than one third of their life in a post-menopausal state. Epidemiological studies indicate that a delayed natural menopause confers longevity and decelerates the appearance of much age-related morbidity, suggesting that developing treatments to delay menopause would significantly improve quality of life for women. Although menopause is ultimately defined by ovarian follicular exhaustion, several lines of scientific evidence in humans and animals now suggest that dysregulation of estradiol feedback mechanisms and hypothalamic-pituitary dysfunction contributes to the onset and progression of reproductive senescence, independent of ovarian failure. This article provides a brief update on our current understanding of the role of the hypothalamic-pituitary axis in the onset of and transition into female reproductive senescence.

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Aging alters norepinephrine release in the medial preoptic area in response to steroid priming in ovariectomized rats

Cited by 22 publications

References 25 publications

Interleukin-1 beta simultaneously affects the stress and reproductive axes by modulating norepinephrine levels in different brain areas

Interleukin-1 beta simultaneously affects the stress and reproductive axes by modulating norepinephrine levels in different brain areas

Restoration of the Luteinizing Hormone Surge in Middle-Aged Female Rats by Altering the Balance of GABA and Glutamate Transmission in the Medial Preoptic Area1

The neuroendocrine physiology of female reproductive aging: An update

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