Preoptic Catecholamine, GABA, and Glutamate Release in Ovariectomized and Ovariectomized Estrogen-Primed Rats Utilizing a Push-Pull Cannula Technique

Demling, Joachim; Fuchs, Eberhard; Baumert, Marion; Wuttke, W.

doi:10.1159/000124180

Cited by 162 publications

(111 citation statements)

References 21 publications

(42 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…During this period iri our study, GABA release gradually declined and reached stable levels at the time of the initial increase in LH/LHRH. A decline in GABA levels in the medial POA prior to the surge has been reported in the rat by Wuttke's group using the techniques of push-pull and focal perfusion (18,31). In these studies the fall in GABA was coincident with or preceded the surge by, at most, an hour whereas in the present study GABA levels began a slow decline some 10 h in advance of the first rise in LH.…”

Section: Poasupporting

confidence: 56%

“…GABA neurons, by virtue of the fact that some of them form synaptic connections with LHRH neurons in the POA (1 1) and that a proportion of these possess receptors for oestrogen (14,15), might subserve this function. It has been shown that oestrogen increases GABA release from the POA (18,19) and that GABA can alter LH secretion (20)(21)(22)(23)(24)(25)(26)(27)(28). A role for GABA in the LH surge had been suggested by two types of experiment.…”

Section: Poamentioning

confidence: 99%

See 1 more Smart Citation

Changes in the Release of Gamma‐Aminobutyric Acid and Catecholamines in the Preoptic/Septal Area Prior to and During the Preovulatory Surge of Luteinizing Hormone in the Ewe

Robinson

Kendrick

Lambart

1991

J Neuroendocrinology

View full text Add to dashboard Cite

The technique of intracranial microdialysis was used to monitor changes in the outflow of the catecholamines, noradrenaline, adrenaline and dopamine and the inhibitory amino-acid y-arninobutyric acid (GABA) in the preopticlseptal area of the conscious ewe during an oestradiol-induced surge of luteinizing hormone (LH). The s a m e animals were sampled twice from an identical brain site, once in the presence of oestradiol and once in its absence, when no surge occurred and LH levels remained low. Changes in the outflow of GABA, noradrenaline and adrenaline (but not dopamine) were related to changes in LH secretion. Specifically, GABA outflow was maximal in the h o u r s following oestradiol administration but began a sustained fall some 10 h before the surge began, to level off just before the first increment in LH secretion. Low GABA concentrations were maintained until after gonadotrophin levels had once more returned to baseline. The release of all three catecholamines was pulsatile. Noradrenergic activity was greater in the presence of oestradiol although activity did not alter over t h e 20 h of sampling. The pulse frequency of adrenaline was maximal in the h o u r s immediately prior to the LH surge and minimal in the hours following its initiation. These data suggest that a decrease in GABAergic transmission in t h e vicinity of t h e LH-releasing hormone cell bodies is a necessary component of the neural mechanism by which the oestradiol-induced surge of LH is generated. A general increase in noradrenergic activity coupled with changes in the release of adrenaline at t h e time of the surge may be additional prerequisites for successful ovulation.The hormonal events which are required to elicit the massive increment in luteinizing hormone (LH) secretion necessary to cause ovulation are relatively well understood and allow us, to some degree, to manipulate both our own fertility and that of other species ( I , 2). In contrast, the neural events which are a prerequisite for the LH surge remain largely enigmatic.Our knowledge has recently been extended by data demonstrating conclusively that the oestradiol-induced LH surge in the ewe results from a massive increase in the secretion of LH-releasing hormone (LHRH) into the portal vessels from nerve terminals located in the median eminence (3, 4). The cell bodies of these LHRH neurons are located in the preoptic and septa1 areas (POA/S) of the ovine brain ( 5 ) but as these cells d o not themselves possess oestrogen receptors (6), other steroid-sensitive neural elements must mediate oestrogen effects on LH. In relation to this, the POA is innervated by neurons containing the catecholamine neurotransmitters noradrenaline (NA; 7, 8) adrenaline (A; 9) and dopamine (DA; 10) and the inhibitory amino-acid y-aminobutyric acid (GABA; 1 I , 12). NA and GABA neurons have been shown to concentrate oestrogen (1 3-1 5 ) and all four neuroactive substances have been implicated in mediating the actions of gonadal steroids on LH secretion (16,17). This study sought to d...

show abstract

Section: Poasupporting

confidence: 56%

Section: Poamentioning

confidence: 99%

Changes in the Release of Gamma‐Aminobutyric Acid and Catecholamines in the Preoptic/Septal Area Prior to and During the Preovulatory Surge of Luteinizing Hormone in the Ewe

Robinson

Kendrick

Lambart

1991

J Neuroendocrinology

View full text Add to dashboard Cite

show abstract

“…Estrogen activation of brainstem noradrenergic neurons (Jennes et al 1992) and an increment in hypothalamic NA turnover in response to estrogen treatment is well established (Honma & Wuttke 1980, Wise et al 1981, Demling et al 1985, Liaw et al 1992. Therefore, increase in ERa colocalized within the noradrenergic neurons of the A2 region during fasting suggests that estrogen could increase the activation of A2 noradrenergic neurons, thereby increasing NA transmission from the A2 region to the PVN and enhancing the suppression of LH secretion.…”

Section: Discussionmentioning

confidence: 98%

Temporal expression of estrogen receptor α in the hypothalamus and medulla oblongata during fasting: a role of noradrenergic neurons

Reyes¹,

Tsukamura²,

I’Anson³

et al. 2006

Journal of Endocrinology

View full text Add to dashboard Cite

Fasting-induced LH suppression is augmented by estrogen in female rats. We investigated the temporal changes in the number of estrogen receptor a (ERa)-immunoreactive (ir) cells in various brain regions in ovariectomized rats fasted for 6, 24, 30, and 48 h, commencing at 1300 h. We also determined the anatomical relationship of ERa immunoreactivity and dopamine-b-hydroxylase (DBH) neurons in the A2 region of the nucleus of the solitary tract (NTS) and the paraventricular nucleus (PVN). The number of ERa-ir cells significantly increased after 30 h from the onset of fasting in the PVN and NTS compared with the unfasted controls and was sustained until 48 h. In the A2 region of 48-h fasted rats, 46$75% DBH-ir cells expressed ERa, and this was significantly higher than in unfasted controls (8$16% DBH-ir cells expressed ERa). In the PVN, most ERa-ir neurons were juxtaposed with DBH-ir varicosities. These results suggest that ERa is expressed in specific brain regions at a defined time from the onset of fasting. In addition, the anatomical relationship of noradrenergic and ERa-ir neurons in the A2 region and PVN may suggest a role for estrogen in increasing the activity of noradrenergic neurons in the A2 region and enhancing sensitivity of the PVN to noradrenergic input arising from the lower brainstem and thereby augmenting the suppression of LH secretion during fasting.

show abstract

“…Until now, the only identified oestrogen-receptive population in the MPOA has been one containing the inhibitory neurotransmitter ?-aminobutyric acid (GABA) (7). Recent work suggests that GABA neurons in the MPOA are partly responsible for mediating feedback effects of oestrogen to the LHRH neurons and generating the LH surge (8)(9)(10). However, the neurochemical nature of the other oestrogen-receptive cells in the MPOA must be determined before a full understanding of oestrogen actions in this area is attained.…”

mentioning

confidence: 99%

Neurotensin‐lmmunoreactive Neurons in the Rat Medial Preoptic Area are Oestrogen‐Receptive

Herbison¹,

Theodosis²

1991

J Neuroendocrinology

View full text Add to dashboard Cite

The identity of neurons influenced by oestrogen is critical for the understanding of ovarian steroid actions in the brain. The medial preoptic a r e a (MPOA) contains one of the largest oestrogen-receptive cell populations in the rat brain and participates in several oestrogen-dependent functions, including the regulation of luteinizing hormone (LH) secretion and sexual behaviour. Using double immunostaining procedures with antibodies specific for the oestrogen receptor and neurotensin, a neuropeptide implicated in the regulation of LH secretion within this area, we found that approximately half of the neurotensin-immunoreactive neurons in the MPOA also displayed immunoreactivity for the oestrogen receptor. We estimate that oestrogen-receptive neurotensin neurons represent 5% to 12% of all oestrogen receptor-positive cells in the MPOA. Our results provide morphological evidence that neurotensin mediates oestrogendependent mechanisms within the brain and suggest that oestrogen may act through preoptic neurotensin neurons to aid in the generation of the LH surge.The MPOA contains one of the largest populations of oestrogenreceptive neurons in the rat brain (1, 2) and plays a key role in reproductive neuroendocrine (3) and behavioural (4) pathways, both of which are oestrogen-dependent. In order to understand how oestrogen modulates neural activity within the MPOA it is necessary to identify the neural populations influenced by this ovarian steroid. This need is highlighted by our present understanding of how oestrogen controls the secretion of LH. Although oestrogen is known to act in the MPOA to evoke the preovulatory LH surge (3, 5), the LH-releasing hormone (LHRH) neurons themselves are unable to concentrate oestrogen (6). Until now, the only identified oestrogen-receptive population in the MPOA has been one containing the inhibitory neurotransmitter ?-aminobutyric acid (GABA) (7). Recent work suggests that GABA neurons in the MPOA are partly responsible for mediating feedback effects of oestrogen to the LHRH neurons and generating the LH surge (8)(9)(10). However, the neurochemical nature of the other oestrogen-receptive cells in the MPOA must be determined before a full understanding of oestrogen actions in this area is attained.Within the MPOA, neurotensin appears to be important in modulating the activity of LHRH neurons at the time of the LH surge. Neurotensin exerts a stimulatory influence on the magnitude of the LH surge (1 1, 12) and oestrogen modulates neurotensin/neuromedin N mRNA expression within the MPOA of ovariectomized rats (1 3). These observations suggest that neurotensin-containing neurons in the MPOA are a target for oestrogen in stimulating the activity of LHRH neurons. As the distribution of neurotensin-immunoreactive neurons in the MPOA (14, 15) appears to overlap that of the oestrogen-receptive cells (1, 2), we investigated the possibility that neurotensin neurons are another oestrogen-receptive population in the MPOA.In agreement with earlier studies (2, 16, 17) using the now well chara...

show abstract

Preoptic Catecholamine, GABA, and Glutamate Release in Ovariectomized and Ovariectomized Estrogen-Primed Rats Utilizing a Push-Pull Cannula Technique

Cited by 162 publications

References 21 publications

Changes in the Release of Gamma‐Aminobutyric Acid and Catecholamines in the Preoptic/Septal Area Prior to and During the Preovulatory Surge of Luteinizing Hormone in the Ewe

Changes in the Release of Gamma‐Aminobutyric Acid and Catecholamines in the Preoptic/Septal Area Prior to and During the Preovulatory Surge of Luteinizing Hormone in the Ewe

Temporal expression of estrogen receptor α in the hypothalamus and medulla oblongata during fasting: a role of noradrenergic neurons

Neurotensin‐lmmunoreactive Neurons in the Rat Medial Preoptic Area are Oestrogen‐Receptive

Contact Info

Product

Resources

About