THE ROLE OF OESTROGENS IN SPONTANEOUS OVULATION: LOCATION OF SITE OF ACTION OF POSITIVE FEEDBACK OF OESTROGEN BY INTRACRANIAL IMPLANTATION OF THE ANTI-OESTROGEN I.C.I. 46474

SUMMARY In an attempt to locate the site(s) of action of the positive feedback of oestrogen for ovulation, a potent anti-oestrogen, I.C.I. 46474, was stereotaxically implanted into various parts of the brain or into the anterior pituitary. A dose of 5 μg of the anti-oestrogen when implanted into the cerebral cortex or injected subcutaneously on the morning of the day before pro-oestrus in 4-day cyclic rats was only marginally active in interfering with ovulation. By contrast, when the same amount was implanted into the median eminence region or the anterior pituitary, ovulation failed to occur in 80–100% of the rats (P < 0·05). Implantation of the cocoa butter vehicle alone into these regions interfered with ovulation in less than 35% of animals. Introduction of the anti-oestrogen into the anterior hypothalamic or mammillary region gave equivocal results. The data suggest that both the median eminence and the anterior pituitary contain receptors which can be blocked by the anti-oestrogen with resultant inhibition of ovulation. It is concluded that the positive feedback of oestrogen for ovulation is exerted both at the pituitary and the hypothalamic levels.

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INHIBITION OF OVULATION IN THE RAT BY INTRAHYPOTHALAMIC IMPLANTS OF AN ANTIOESTROGEN

Journal of Endocrinology ◽

10.1677/joe.0.0560585 ◽

1973 ◽

Vol 56 (3) ◽

pp. 585-590 ◽

Cited By ~ 13

Author(s):

ROLAND BILLARD ◽

P. G. McDONALD

Keyword(s):

Cocoa Butter ◽

Median Eminence ◽

Positive Feedback ◽

Anterior Pituitary ◽

Critical Period ◽

Preoptic Area ◽

Preoptic Region

SUMMARY In order to determine the sites at which oestradiol exerts its positive feed back effect, double-walled cannulae containing the antioestrogen ICI 46,474 were implanted into the preoptic area, median eminence or anterior pituitary. Implants were made at different stages of the cycle and left in place for between 4 and 96 h. Implants in the preoptic area for 24, 48 or 96 h did not significantly inhibit ovulation. Implants placed in the median eminence for 24 h before the critical period significantly inhibited ovulation when compared with controls (P < 0·02). Implantation of antioestrogen in the anterior pituitary for a similar 24-h period was ineffective in blocking ovulation. However, when mixed with cocoa butter and implanted in the anterior pituitary the antioestrogen significantly inhibited ovulation (P < 0·02). The results show that by preventing the action of oestradiol on either the pituitary or the median eminence, ovulation may be inhibited. Ovulation was not affected by implants in the preoptic region which suggests that this area is not involved in the positive feedback action of oestradiol.

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The human brain: Chairman’s introduction

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1981.0023 ◽

1981 ◽

Vol 292 (1057) ◽

pp. 151-153

Keyword(s):

Human Brain ◽

Cultural Evolution ◽

Positive Feedback ◽

Time Scale ◽

Biological Evolution ◽

Internal Models ◽

Adaptive Behaviour ◽

Myelin Sheaths ◽

The Brain

Much has been said at the symposium about the pre-eminent role of the brain in the continuing emergence of man. Tobias has spoken of its explosive enlargement during the last 1 Ma, and how much of its enlargement in individual ontogeny is postnatal. We are born before our brains are fully grown and ‘wired up ’. During our long adolescence we build up internal models of the outside world and of the relations of parts of our bodies to it and to one another. Neurons that are present at birth spread their dendrites and project axons which acquire their myelin sheaths, and establish innumerable contacts with other neurons, over the years. New connections are formed; genetically endowed ones are stamped in or blanked off. People born without arms may grow up to use their toes in skills that are normally manual. Tobias, Darlington and others have stressed the enormous survival value of adaptive behaviour and the ‘positive feedback’ relation between biological and cultural evolution. The latter, the unique product of the unprecedentedly rapid biological evolution of big brains, advances on a time scale unknown to biological evolution.

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METABOLISM OF TESTOSTERONE IN THE ANTERIOR PITUITARY GLAND AND THE CENTRAL NERVOUS SYSTEM OF THE EUROPEAN STARLING (STURNUS VULGARIS)

Journal of Endocrinology ◽

10.1677/joe.0.0750347 ◽

1977 ◽

Vol 75 (3) ◽

pp. 347-354 ◽

Cited By ~ 68

Author(s):

R. MASSA ◽

L. CRESTI ◽

L. MARTINI

Keyword(s):

Central Nervous System ◽

Pituitary Gland ◽

Anterior Pituitary ◽

Sturnus Vulgaris ◽

European Starling ◽

European Starlings ◽

The Central Nervous System ◽

The Brain

The metabolism of testosterone was studied in vitro in anterior pituitary, hypothalamic and hyperstriatal tissues taken from male European starlings in the autumn. In all the tissues studied, testosterone was converted into 5α-androstan-17β-ol-3-one (5α-DHT), 5β-androstan-17β-ol-3-one (5β-DHT), 5β-androstane-3α,17β-diol (5β-THT), 5β-androstane-3,-17-dione and androst-4-ene-3,17-dione. The 5α-DHT was produced in significantly greater amounts by the pituitary gland than by the hypothalamus and hyperstriatum. The amount of 5α-DHT produced, however, was very low in comparison with the amounts of 5β-reduced metabolites. The amount of 5β-reductase was also higher in the pituitary gland than in the two nervous tissues. The ratios between the production of 5β-DHT, 5β-THT and 5β-androstane-3,17-dione were, however, different in the three tissues: 5β-DHT was produced in the greatest quantities by the hyperstriatum, while the production of 5β-THT, 5β-androstane-3,17-dione and androst-4-ene-3,17-dione was greatest in pituitary tissue. The role of 5α- and 5β-reduced metabolites in the pituitary gland and in the brain of birds is unknown, but some possibilities arising from the present results are discussed.

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Learning to see in 3D with two eyes: the role of experience, plasticity and neurochemistry

The Biochemist ◽

10.1042/bio20200059 ◽

2020 ◽

Vol 42 (5) ◽

pp. 12-17

Author(s):

Betina Ip ◽

Holly Bridge

Keyword(s):

Cerebral Cortex ◽

Binocular Vision ◽

Early Experience ◽

Fine Tuning ◽

Computational Power ◽

The World ◽

Accurate Performance ◽

The Brain ◽

Binocular Depth

Humans, along with other predators, have forward-facing eyes which restrict the area of the world that can be seen when compared to animals with eyes on the side of the head. Why would we sacrifice this panoramic vision? The answer is the very precise ability that having two eyes with overlapping and slightly different viewpoints provides to determine fine differences in depth. While interpreting this type of ‘binocular depth’ appears effortless, the precise calculations necessary for perceiving binocular depth require significant computational power in the cerebral cortex and the fine tuning of neurochemical interactions. This processing occurs in the visual regions of the brain and must be honed through early experience for accurate performance. By considering each stage of binocular processing and the neurochemical interactions required for integrating signals from the two eyes, we can begin to understand how the inherent ability of the brain to learn might help us when binocular vision goes wrong.

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EFFECTS OF ANTIBODY TO OESTROGEN OR OF OVARIECTOMY ON THE INCORPORATION OF [35S]METHIONINE INTO BRAIN PROTEIN AND ON GONADOTROPHIN LEVELS DURING THE OESTROUS CYCLE IN THE RAT

Journal of Endocrinology ◽

10.1677/joe.0.0650399 ◽

1975 ◽

Vol 65 (3) ◽

pp. 399-410 ◽

Cited By ~ 3

Author(s):

M. B. TER HAAR ◽

P. C. B. MACKINNON

Keyword(s):

Median Eminence ◽

Anterior Pituitary ◽

Preoptic Area ◽

Oestrous Cycle ◽

Apparent Discrepancy ◽

Brain Protein ◽

Brain Areas ◽

Oestradiol Benzoate ◽

Endogenous Oestrogen ◽

The Brain

SUMMARY The incorporation of [35S]methionine into protein of the anterior pituitary and discrete brain areas was measured following the administration of antibodies to oestrogen, ovariectomy, or adrenalectomy on the afternoon of dioestrus. The antibody to oestrogen deleted the circadian rhythms of methionine incorporation normally observed in the various brain areas together with the peaks of incorporation normally observed in the median eminence area and anterior pituitary on the evening of pro-oestrus. The peaks of incorporative activity normally observed in the preoptic area and amygdala (relative to the putamen) at 03.00 h on the day of pro-oestrus were also deleted. Administration of the antiserum on the morning of pro-oestrus failed to alter the pattern of methionine incorporation normally observed on the evening of pro-oestrus. Ovariectomy performed at 16.00 h of dioestrus blocked the preovulatory rise of luteinizing hormone (LH) (as did the antibody to oestrogen) and inhibited the peak of methionine incorporation normally observed in the anterior pituitary on the evening of pro-oestrus. However, for the peak in the median eminence to be inhibited, ovariectomy had to be performed on the morning of the preceding oestrus. Adrenalectomy alone, or adrenalectomy with ovariectomy, performed on the afternoon of dioestrus did not affect the levels of methionine incorporation in the brain or anterior pituitary at 18.00 h on the day of prooestrus. Animals which had been ovariectomized and injected with 2·5 μg oestradiol benzoate on the morning of oestrus showed significantly increased levels of methionine incorporation in all the brain areas and the anterior pituitary at 18.00 h of expected pro-oestrus. The administration of antibody to oestrogen to a similar group of animals on the afternoon of expected dioestrus inhibited the rise at 18.00 h of expected pro-oestrus. The apparent discrepancy between the results obtained with ovariectomy and the antiserum appeared to be due to the ability of the antiserum to neutralize the activity of oestrogens retained by the tissues. The present results suggest that the changes in incorporation of methionine into protein in the brain and anterior pituitary are brought about by the action of endogenous oestrogen: there appears to be a steady summative effect on the median eminence throughout the oestrous cycle together with a short-lived effect occurring during pro-oestrus and affecting the anterior pituitary.

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OVARIAN STEROID EFFECTS ON GONADOTROPHIN OUTPUT, AND ON THE INCORPORATION OF 35S FROM METHIONINE INTO PROTEIN OF DISCRETE BRAIN AREAS AND THE ANTERIOR PITUITARY

Acta Endocrinologica ◽

10.1530/acta.0.0850279 ◽

1977 ◽

Vol 85 (2) ◽

pp. 279-290

Author(s):

M. B. ter Haar ◽

P. C. B. MacKinnon

Keyword(s):

Luteinizing Hormone ◽

Median Eminence ◽

Anterior Pituitary ◽

Preoptic Area ◽

Ovarian Hormones ◽

Female Rats ◽

Brain Areas ◽

Lh Surge ◽

Progesterone Metabolites ◽

The Brain

ABSTRACT The effects of various ovarian hormones administered on the morning of pro-oestrus on gonadotrophin levels and the incorporation of 35S from methionine into protein of discrete areas of the brain and the anterior pituitary were investigated at 15.00 h of the same day in female rats. The hormones which were investigated in this study could be divided in general into two groups according to their actions. The first group, consisting of oestradiol-17β and progesterone, tended to advance the preovulatory surge of luteinizing hormone (LH) by 3–6 h from 18.00–21.00 h, together with the peaks of [35S] incorporation in the median eminence area and the anterior pituitary which normally accompany the LH surge. The second group, consisting of the LH-stimulated reduced progesterone metabolites, 5α-pregnane-3,20-dione (pregnanedione) and 20α-hydroxypregn-4-en-3-one (dihydroprogesterone), tended to inhibit serum gonadotrophin levels as well as inhibiting the pro-oestrous increase of [35S] incorporation in the median eminence area and in the amygdala, but not in the preoptic area and the anterior pituitary. On the afternoon of pro-oestrus in intact animals, luteinizing hormonereleasing hormone or LH administration had the same effect on [35S]incorporation in the brain as did the progesterone metabolites, though this effect was not observed if the animals had been ovariectomized a few hours beforehand. It is suggested that certain ovarian hormones are involved in the neural events which induce the pre-ovulatory LH surge, while others are associated with neural events which terminate the stimulus for the LH surge.

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Fish behaviour

10.1093/oso/9780198785552.003.0014 ◽

2017 ◽

Author(s):

Derek Burton ◽

Margaret Burton

Keyword(s):

Cerebral Cortex ◽

Olfactory Bulb ◽

Optic Tectum ◽

Colour Change ◽

Fish Behaviour ◽

Potential Prey ◽

Complex Behaviour ◽

The Brain

Behaviour involves reacting to stimuli and may be innate (colour change) or include input via cognition (learning, memory). Understanding the complex behaviour of some fish, as in interaction with conspecifics, potential prey or predators, may require consideration of neurobiology and endocrinology. Whereas fish may show behaviours associated with tetrapods (play, sleep), some of their behaviour follows a preset pattern, for example in feeding and reproduction. Communication between fish depends on cues such as colour, sound, electroception or pheromones. Long-term behaviour includes migration and territoriality, with schooling a group phenomenon. Within the brain a neuropil may indicate a region capable of memory, in fish it is abundant in the optic tectum with up to 15 laminae (layers), with some in the olfactory bulb; however, the laminated cerebral cortex of mammals is lacking. Current research includes the role of engrams in memory and the use of zebrafish as models.

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The role of the brain

10.1093/oso/9780198806738.003.0001 ◽

2017 ◽

Author(s):

Ray Guillery

Keyword(s):

Nervous System ◽

Cerebral Cortex ◽

Clinical Condition ◽

The Other ◽

Neural Pathways ◽

Sense Organs ◽

The World ◽

Motor Actions ◽

The Brain

This chapter introduces two interpretations of how we know about the world. One, the standard, sensory-to-motor view, is that physical actions for sounds, lights, tastes, smells, and so on act on our sense organs to produce messages that are sent through the nervous system to the cerebral cortex, where the relevant structures of the world can be recognized and appropriate motor actions can be initiated. The other is an interactive sensorimotor view where the nervous system records our interactions with the world, abstracting our knowledge about the world from these interactions. These two opposing views have rarely been considered in terms of specific neural pathways or the messages that they carry; that is the plan for this book. Each view leads to different sets of interpretations of experiments and to different sets of research proposals. The final part of the chapter explores a well-studied and widely taught clinical condition that illustrates the confusions that can arise when the dual meaning of the driver messages to the thalamus is not recognized.

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