Electrical Stimulation of the Median Eminence in Ovariectomized and Estradiol-Treated Sheep. Increased LH Release and Evidence for Neural Regulation of Spontaneous LH Rhythms

1975 ◽  
Vol 19 (1) ◽  
pp. 81-90 ◽  
Author(s):  
P.V. Malven
Keyword(s):  
Electrical Stimulation ◽  
Median Eminence ◽  
Neural Regulation ◽  
Lh Release ◽  
Stimulation Of

ADENOHYPOPHYSEAL LH CONTENT IN NORMAL, ANDROGEN-STERILIZED AND PROGESTERONE-PRIMED STERILE FEMALE RATS

1962 ◽  
Vol 39 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Roger A. Gorski ◽  
Charles A. Barraclough
Keyword(s):  
Ascorbic Acid ◽  
Electrical Stimulation ◽  
Quantitative Determination ◽  
Median Eminence ◽  
Hypothalamic Stimulation ◽  
Female Rats ◽  
Rat Pituitary ◽  
Gland Content ◽  
Stimulation Of

ABSTRACT We have previously suggested that the failure of the androgen-sterilized, persistent-oestrous rat to ovulate, following electrical stimulation of the median eminence structures of the hypothalamus, is due to an insufficiency in adenohypophyseal LH concentration. Using the ovarian ascorbic acid technique for quantitative determination of pituitary LH content, the present studies have demonstrated that the sterile rat pituitary gland contains one-third the LH content of the normal prooestrous gland. Furthermore, not only does progesterone priming of this persistent-oestrous rat result in a 75 % increase in LH concentration, but on hypothalamic stimulation sufficient LH is released to induce ovulation. The decrease in LH concentration which accompanies ovulation in the progesterone-primed, sterile rat is approximately 45 % of the total gland content as compared with a 51 % decrease in pituitary content in the normal cyclic rat.

Hemodynamic effects of electrical stimulation of forebrain angiotensin and osmosensitive sites

1978 ◽  
Vol 235 (4) ◽  
pp. H445-H451 ◽  
Keyword(s):  
Blood Flow ◽  
Electrical Stimulation ◽  
Arterial Pressure ◽  
Median Eminence ◽  
Regional Blood Flow ◽  
Renal Hypertension ◽  
Brain Structures ◽  
Ventromedial Hypothalamus ◽  
Pressure Changes ◽  
Stimulation Of

Previous studies from this laboratory have indicated an important role for angiotensin-sensitive anteroventral third ventricular (AV3V) brain structures in normal regulation of arterial pressure and development of renal hypertension. The present experiments examined the effects of electrical stimulation of these periventricular areas on arterial pressure and regional blood flow in the anesthetized rat. Electrodes were placed in the AV3V region 3–10 days prior to acute studies. Blood flow was measured in extracorporeal blood flow circuits. Electrical stimulation produced only small changes in arterial pressure. Despite the small pressure changes, stimulation caused marked frequency-dependent alterations in regional blood flow. Renal and splanchnic flows were reduced while hindlimb flow was increased. Resistance changes were abolished by surgical denervation or ganglionic blockade but were unaffected by adrenalectomy. Hemodynamic responses to AV3V stimulation were abolished by a lesion in the area of the median eminence. It may be concluded that AV3V stimulation, through activation of pathways descending through the ventromedial hypothalamus-median eminence region, produces profound regional blood flow shifts without greatly altering arterial pressure.

LESIONS OF THE SUPRACHIASMATIC NUCLEI AND THE SEROTONIN-DEPENDENT PHASIC RELEASE OF LUTEINIZING HORMONE IN THE RAT: EFFECTS ON DRINKING RHYTHMICITY AND ON THE CONSEQUENCES OF PREOPTIC AREA STIMULATION

1980 ◽  
Vol 84 (2) ◽  
pp. 231-236 ◽  
Author(s):  
C. W. COEN ◽  
P. C. B. MacKINNON
Keyword(s):  
Electrical Stimulation ◽  
Luteinizing Hormone ◽  
Preoptic Area ◽  
Ovariectomized Rats ◽  
Suprachiasmatic Nuclei ◽  
Lh Release ◽  
Radiofrequency Lesions ◽  
Pharmacological Manipulations ◽  
Stimulation Of ◽  
Phasic Release

Ovariectomized rats in which <7% of the suprachiasmatic nuclei had been spared by bilateral radiofrequency lesions were distinguishable from those with >40% of the nuclei by their consistent failure to show the oestrogen-induced daily surge of LH, either with or without pharmacological manipulations of serotonin (5-HT), and also by their loss of the normal rhythmicity of drinking. Minor damage to structures adjacent to the suprachiasmatic nuclei was similar in both groups. The identical facility with which electrical stimulation of the preoptic area induced LH release in the two groups of animals suggested that they were not characterized by different degrees of damage to the preopticotuberal pathway. These results are considered in relation to evidence indicating that the suprachiasmatic nuclei represent the densest concentration of 5-HT terminals in the forebrain and also the site of a mechanism involved in the generation of circadian rhythms.

Plasma LH levels following electrochemical stimulation of the deafferented medial basal hypothalamus

1980 ◽  
Vol 94 (1) ◽  
pp. 11-17
Author(s):  
A. J. Carrillo ◽  
N. Hagino ◽  
G. Setalo
Keyword(s):  
Median Eminence ◽  
Jugular Vein ◽  
External Jugular Vein ◽  
Female Rats ◽  
Medial Basal Hypothalamus ◽  
Blood Samples ◽  
Ether Anaesthesia ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Stimulation Of

Abstract. We have investigated the capability of a completely deafferented medial basal hypothalamus (MBH) pituitary complex to support LH release following electrochemical stimulation (ECS) of the arcuate-median eminence (ARC-ME) region. In adult female rats the MBH was completely deafferented (CD) on the morning of pro-oestrus (08.00-10.00 h of day 0). In the first experiment the animals were divided into 5 groups depending on the day of ECS (14.00–16.00 h) and oestradiol benzoate (Oe) treatment (08.00–10.00 h): group No. 1) ECS on day 0; 2) no ECS; 3) ECS on day 1; 4) Oe on day 0 and ECS on day 1; 5) Oe on day 4 and ECS on day 5. Blood samples were collected from the external jugular vein under ether anaesthesia for LH determinations just before and 1 and 2 h after ECS. ECS on day 0 resulted in a significant (P<0.01) rise in plasma LH at 1 and 2 h, while the rats subjected to CD, but not ECS failed to show any changes in plasma LH levels. ECS on days I and 5 (groups 3 and 5) failed to alter plasma LH levels, however, ECS on day 1 in Oe treated rats produced a significant (P < 0.01) elevation in plasma LH that was comparable to that of day 0. In a second experiment Oe was injected on days 1–5 and ECS of the ARC-ME was done bilaterally. ECS on day 5 resulted in a significant (P < 0.05) rise in plasma LH levels in rats with a completely deafferented MBH. In animals with an incomplete deafferentation ECS resulted in a much greater (P < 0.005) rise in plasma LH at l and 2 h. Since LH was released several days after complete hypothalamic deafferentation, these data suggest that LRH secreting cells may be present within the MBH of the rat. In a third experiment injection of LRH (400 ng) on days 0, 1 and 5 with Oe on days 0, 4 or 1–5 resulted in a significant (P < 0.001) rise of plasma LH at 30 and 60 min in all groups. Rats injected on day 0 showed the greatest elevation at 60 min in all groups. Saline injected rats did not show any changes in plasma LH levels.

Electrochemical Stimulation of the Median Eminence Evokes FSH but not LH Release After LHRH Antagonist Treatment

1998 ◽  
Vol 10 (3) ◽  
pp. 231-236 ◽  
Author(s):  
Miklós Koppán ◽  
Magdolna Kovács ◽  
Imre Mezö ◽  
Béla Flerkó
Keyword(s):  
Median Eminence ◽  
Lhrh Antagonist ◽  
Lh Release ◽  
Stimulation Of

IMMUNOREACTIVE LUTEINIZING HORMONE RELEASING FACTOR IN PITUITARY STALK BLOOD FROM FEMALE RATS: SEX STEROID MODULATION OF RESPONSE TO ELECTRICAL STIMULATION OF PREOPTIC AREA OR MEDIAN EMINENCE

1976 ◽  
Vol 70 (3) ◽  
pp. 501-511 ◽  
Author(s):  
NANCY M. SHERWOOD ◽  
SHARON A. CHIAPPA ◽  
G. FINK
Keyword(s):  
Electrical Stimulation ◽  
Median Eminence ◽  
Preoptic Area ◽  
Neural Mechanism ◽  
Female Rats ◽  
Pituitary Stalk ◽  
Facilitatory Effect ◽  
Sex Steroid ◽  
Female Rat ◽  
Stimulation Of

SUMMARY The effects of sex steroid hormones on the responsiveness of the neural mechanism responsible for the secretion of LH-RF have been examined in the female rat. Responsiveness was determined at pro-oestrus by measuring the increments in immunoreactive LH-RF of pituitary stalk blood produced by electrical stimulation of the medial preoptic area or median eminence. Ovariectomy on the morning of dioestrus reduced the LH-RF response to preoptic stimulation while oestradiol benzoate (OB) or testosterone propionate (TP) administered immediately after ovariectomy significantly augmented the response. The facilitatory effect of TP was possibly due to its conversion to an aromatized derivative since 5α-dihydrotestosterone monobenzoate was ineffective. Progesterone did not facilitate preoptic responsiveness, and, when administered to animals ovariectomized at 12.00 h of pro-oestrus, reduced the LH-RF response at 18.00 h the same day. Stimulation of the median eminence produced a significantly greater increment in LH-RF than stimulation of the preoptic area. The facilitatory action of OB on the LH-RF response was less marked for median eminence compared with preoptic stimulation. The administration of ICI 46474 at 17.00 h of dioestrus did not reduce preoptic responsiveness on the morning of the next day, suggesting that this compound does not act as an 'antioestrogen' at the level of the preoptic area.

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