Glutamate receptors in the rat hypothalamus and pituitary.

Meeker, Rick B.; Greenwood, Robert; Hayward, James N.

doi:10.1210/endo.134.2.7905409

Cited by 141 publications

(78 citation statements)

References 26 publications

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“…The presence of both NMDA and AMPA receptors in the DMH is well established by a variety of techniques, including receptor binding (Meeker et al, 1994), electrophysiology (Bailey et al, 2003), and pharmacological studies (Soltis and DiMicco, 1991;Bailey and DiMicco, 2001;Goren et al, 2003) (see also Introduction). However, the functional roles of the different glutamate receptors in the DMH appear to be much more complex.…”

Section: Discussionmentioning

confidence: 99%

Panic-Prone State Induced in Rats with GABA Dysfunction in the Dorsomedial Hypothalamus Is Mediated by NMDA Receptors

Johnson

Shekhar

2006

J. Neurosci.

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Section: Discussionmentioning

confidence: 99%

Panic-Prone State Induced in Rats with GABA Dysfunction in the Dorsomedial Hypothalamus Is Mediated by NMDA Receptors

Johnson

Shekhar

2006

J. Neurosci.

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“…In theory, an inhibitory effect at pituitary level, an increase in dopamine release or a decrease in the secretion of hypothalamic PRFs might be responsible for the inhibitory effect of AMPA. Despite the presence of AMPA receptors in pituitary gland (Kiyama et al 1993, Meeker et al 1994, Bhat et al 1995, Villalobos et al 1996, the only pituitary effect observed was a weak stimulatory action after incubation of hemipituitaries with 10 8 M AMPA. The results strongly suggest that the activation of AMPA receptors does not affect the secretion of PRL via a pituitary mechanism.…”

Section: Discussionmentioning

confidence: 97%

Regulation of prolactin secretion by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors in male rats

Gonzalez

Pinilla²,

Tena‐Sempere

et al. 2000

Journal of Endocrinology

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The secretion of PRL is controlled by different hypothalamic signals. Depending on the experimental model, PRL secretion increases or decreases after activation of N-methyl--aspartic acid and kainate receptors. Recently we have described that activation of -amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors inhibits PRL secretion in prepubertal male rats. The aim of present study was to examine (1) the physiological relevance of this finding, (2) the possible age-related changes observed after activation or blockade of AMPA receptors, (3) the specificity of the AMPA effect, (4) the hypothalamic and/or pituitary localization of AMPA action, and (5) the mechanism(s) of action of AMPA agonists.In a first set of experiments, neonatal males (5 and 10 days old) and prepubertal (23 days old) male rats were injected with AMPA (1, 2·5 or 5 mg/kg) or the antagonist of AMPA receptors 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo (f) quinoxaline-7-sulfonamide (NBQX; 0·25 or 0·50 mg/kg). Serum PRL concentrations decreased significantly 15 and 30 min after i.p. administration of AMPA in prepubertal male rats, while the inhibitory effect of AMPA was not observed in 5-and 10-day-old males. The effect of AMPA was abolished by NBQX but not by MK-801 (a selective antagonist of NMDA receptors). NBQX alone (0·25 or 0·50 mg/kg) had no effect on PRL release. In vitro, AMPA slightly stimulated PRL secretion by hemipituitaries from prepubertal males, suggesting that the hypothalamus is likely the site of action for the reported inhibitory action of AMPA on PRL release. In this sense, the blockade of AMPA effects in animals pretreated with domperidone (a dopaminergic antagonist) or -methyl-p-tyrosine (an inhibitor of dopamine synthesis) suggests that an increase in the release of hypothalamic dopamine is probably the mechanism involved in the effect of AMPA. In a second set of experiments, the effects of AMPA (2·5 mg/kg i.p.) and NBQX (0·5 mg/kg i.p. and 20 or 40 nmol i.c.v.) were tested in freely moving adult male rats sampled during periods of 2, 3 or 6 h. In contrast with data obtained in prepubertal rats, neither AMPA nor NBQX affected PRL secretion.In conclusion, these data indicate that activation of AMPA receptors inhibits PRL secretion in prepubertal male rats. This effect probably involves the release of dopamine from the hypothalamus and disappears in adulthood.

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“…Current research is occupied with trying to elucidate which subunit combinations are found in which parts of the brain and trying to understand why neurons employ different subtypes of receptor. Binding of subtype specific agonists and antagonists for each major EAA receptor subtype is present in all hypothalamic and preoptic regions with relative densities NMDA > metabotropic receptor > kainate and AMPA (Meeker et al 1994). Receptor autoradiography reveals regional densities of EAA receptors to be ventromedial, dorsal medial> paraventricular, anterior hypothalamic, supraoptic> arcuate, suprachiasmatic, lateral hypothalamic > pre-optic area (Meeker et al 1994).…”

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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Glutamate receptors in the rat hypothalamus and pituitary.

Cited by 141 publications

References 26 publications

Panic-Prone State Induced in Rats with GABA Dysfunction in the Dorsomedial Hypothalamus Is Mediated by NMDA Receptors

Panic-Prone State Induced in Rats with GABA Dysfunction in the Dorsomedial Hypothalamus Is Mediated by NMDA Receptors

Regulation of prolactin secretion by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors in male rats

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