Expression of GABAA receptor α2 sub-unit mRNA by periventricular somatostatin neurones in the rat hypothalamus

Herbison, Allan E.; Augood, Sarah J.

doi:10.1016/0304-3940(94)90138-4

Cited by 16 publications

(11 citation statements)

References 18 publications

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“…Thus GABAergic nerve terminals are closely associated with the perikarya and terminals of SRIH neurons [11, 12], both SRIH mRNA expression [13, 14]and SRIH release [15, 16]are modified by GABA A receptor ligands and sex steroids may influence GABA actions on SRIH release in the female in vivo [17]. Furthermore, previous findings in our laboratories have shown that GABA A receptor subunits are found in the majority of PeN SRIH cells [18]. GABA has also been implicated in the generation of sex differences in several brain regions [19, 20], including the GnRH neurons of the hypothalamus [21], and many hypothalamic GABAergic neurons express estrogen receptors [22].…”

Section: Introductionmentioning

confidence: 90%

“…While the great majority of SRIH neurons in the PeN express the α 2 subunit of the GABA A receptor [18], the other GABA A receptor subunits expressed by these cells are unknown and it remains possible that these other subunits and/or the posttranscriptional regulation of GABA A receptors may change during puberty.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, as we have previously shown colocalisation of the α 2 subunit of the GABA A receptor with SRIH-containing cells of the PeN [18], we have begun to address the possibility that sex and developmental differences in GABA A receptor subunit composition may contribute to these differences by determining the expression of mRNA for the α 1 and α 2 receptor subunits in the PeN during pre- and postnatal development and in adult male and female rats.…”

Section: Introductionmentioning

confidence: 99%

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Sexually Dimorphic Ontogeny of GABAergic Influences on Periventricular Somatostatin Neurons

Murray

Rantle²,

Simonian³

et al. 1999

Neuroendocrinology

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The biosynthesis and secretion of somatostatin (SRIH) within the hypothalamic periventricular-median eminence (PeN-ME) pathway follows a sexually differentiated developmental pattern beginning in the early neonatal period. It is generally accepted that testosterone plays a role in these processes, but the mechanisms underlying the age and sex differences are poorly understood. The present study sought to investigate the hypothesis that γ-aminobutyric acid (GABA) may play a role in determining sex differences in SRIH neuronal activity. Using an in vitro hypothalamic preparation where more than 97% of the immunoreactive SRIH is contained within the PeN-ME pathway, peptide release in response to the GABA_A receptor antagonist, bicuculline, was followed through development. In the male a stimulatory response, indicative of an inhibitory GABAergic tone on SRIH secretion, was observed as early as postnatal day (P) 5. This persisted throughout juvenile development (P10, P17) and was present also in the adult male (P75), but in the peripubertal period the response to bicuculline was first lost (P25) and then reversed to an inhibition (P40), suggesting a transient switch to an apparent stimulatory GABAergic tone on SRIH release. By contrast, in the female, no bicuculline responsiveness was seen until P25 when it caused a decrease in SRIH release which persisted into adulthood. Using in situ hybridization studies we found no evidence to support the view that these age- and sex-dependent differences were due to changes in the expression of GABA_A receptor α-subunits (α₁ and α₂) which are colocalised in the PeN SRIH neurons. Following adult gonadectomy, the bicuculline response was abolished in the male, whereas, in the female it was reversed and identical in magnitude to the response in the intact male. These results demonstrate marked sex differences in GABA_A-receptor-mediated influences on SRIH release which develop soon after birth and, in the adult, depend on gonadal factors. In the male these factors activate a primarily inhibitory influence, whereas in the female they facilitate an apparently stimulatory tone of GABA on SRIH secretion via the GABA_A receptor. Our findings thus support the view that GABAergic transmission may play a key role in generating sex differences in the mode of SRIH secretion from the hypothalamus which has been shown to be a major factor in determining the sexually dimorphic patterns of growth hormone secretion.

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Section: Introductionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sexually Dimorphic Ontogeny of GABAergic Influences on Periventricular Somatostatin Neurons

Murray

Rantle²,

Simonian³

et al. 1999

Neuroendocrinology

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“…GnRH neurons in the OVLT/POA are innervated by gamma-aminobutyric acid (GABA)-ergic cells, which are thought to be involved in the negative feedback of E 2 on the LH surge (Miller et al, 2003;Zhen et al, 1997). These GABAergic cells originating from the OVLT/POA innervate SOM neurons in the PeVN and may therefore also be involved in the regulation of GH release from the pituitary (Herbison et al, 1994;Murray et al, 1999;Rage et al, 1993;Willoughby et al, 1987). Also, within the PeVN, a small number of SOM neurons co-express GABA (Tanaka et al, 1997).…”

Section: Effect Of Som On the Reproductive Axismentioning

confidence: 99%

Somatostatin in the Periventricular Nucleus of the Female Rat: Age Specific Effects of Estrogen and Onset of Reproductive Aging

Beek¹,

Vugt²,

Franke³

et al. 2012

Sex Steroids

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“…The cx2 subunit mRNA is abundant in most regions of the hypothalamus. As studied by double-labelling in situ hybridization, the a2 subunit expressing cells of the periventricular nucleus are somatostatin positive, and it seems likely that GABAA receptor activation of these cells regulates somatostatin synthesis (Herbison & Augood, 1994). The acl, a3 and a5 subunit mRNAs are often found in the nuclei that contain a2, but at much lower levels, and yl and y2 mRNA levels are equiabundant.…”

Section: MD Brown School Of Sport and Exercise Sciences University Omentioning

confidence: 99%

Symposium Proceedings

1995

The Journal of Physiology

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Starting with the earliest in vivo studies of the microcirculation, observers have been impressed with the variability and heterogeneity of microcirculation blood flow. The question I should like to address is how heterogeneity of microvascular perfusion influences transport of diffusible solutes, and how control of heterogeneity may contribute to regulation of blood-tissue exchange. Available exchange vessel surface area and inter-exchange vessel distances are controlled at the arteriolar level by the number of vessels open to the supply of arterial blood. When metabolic requirements are low, only a fraction of the exchange vessels in a vascular network are perfused; as metabolic activity increases, more exchange vessels are recruited. However, the efficiency with which available exchange vessel surface is utilized for diffusion of a given solute depends on the distribution of individual blood flow/permeability surface area ratios (Q/PS) in the network. Maximum efficiency (full utilization of available PS) is achieved when Q/PS is uniform.In vivo observations of red blood cell velocities show wide variation among individual exchange vessels of the same class (capillaries, postcapillary venules); presumably the same is true of plasma velocities. Flow velocity is only one of the factors that determines local transport; the critical parameter is the product of velocity and vessel radius divided by vessel length times solute permeability (v. r/ 1 P). The impression I get from published intra-vital microscope data is that this ratio may vary even more widely than velocity alone. Physiological measurements of solute transport in whole organs provide indirect support for broad heterogeneity of perfusion, at least in low metabolic states. In resting skeletal muscles the apparent (measured) PS products for 86Rb and 51Cr EDTA increase with increasing perfusion rate, approaching limiting values at high flow rates, as predicted for a heterogeneity perfused assemblage of exchange vessels. Estimated coefficients of variation (cv = S.D./mean) of Q/PS or v. r/ 1 P lie in the range 07-09.In heterogeneously perfused organs and tissues, the degree of heterogeneity (cv of Q/PS) and the total blood flow are potentially important secondary regulators of capillary transport, because they determine the efficiency with which the primary controlling factors, total blood flow and available exchange vessel surface area, are utilized (note that blood flow acts both directly and indirectly). Efficiency, defined as the ratio of apparent PS to the maximum PS at uniform perfusion, is inversely related to the degree of heterogeneity and directly related to the mean flow velocity. There is conflicting evidence in the literature concerning the degree to which alteration of Q/PS heterogeneity is involved in adaptive control of diffusion exchange. However, even with constant total PS and fixed heterogeneity, an increase in total blood flow can decrease the influence of heterogeneity on transport and thus contribute substantially to Berlin 33, Ger...

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Expression of GABAA receptor α2 sub-unit mRNA by periventricular somatostatin neurones in the rat hypothalamus

Cited by 16 publications

References 18 publications

Sexually Dimorphic Ontogeny of GABAergic Influences on Periventricular Somatostatin Neurons

Sexually Dimorphic Ontogeny of GABAergic Influences on Periventricular Somatostatin Neurons

Somatostatin in the Periventricular Nucleus of the Female Rat: Age Specific Effects of Estrogen and Onset of Reproductive Aging

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