IMMUNOREACTIVE LUTEINIZING HORMONE RELEASING FACTOR IN RAT PITUITARY STALK BLOOD: EFFECTS OF ELECTRICAL STIMULATION OF THE MEDIAL PREOPTIC AREA

1976 ◽  
Vol 68 (1) ◽  
pp. 71-87 ◽  
Author(s):  
G. FINK ◽  
M. G. JAMIESON
Keyword(s):  
Electrical Stimulation ◽  
Preoptic Area ◽  
Free Acid ◽  
Medial Preoptic Area ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Pituitary Stalk ◽  
Male And Female ◽  
Male And Female Rats ◽  
Stimulation Of

SUMMARY Blood was collected from the cut pituitary stalk of male and female rats before and during the application of an electrical stimulus to the medial preoptic area. The plasma was assayed for immunoreactive LH releasing factor (RF) by a double antibody radioimmunoassay using a specific antiserum raised in rabbits against the free acid derivative of the decapeptide LH-RF conjugated to bovine serum albumin. The decapeptide (used as a standard) and pituitary stalk plasma cross-reacted in a similar manner with the antiserum. Stimulation of the preoptic area increased significantly the amount of LH-RF in pituitary stalk plasma in both male and female rats. The increase in LH-RF was linearly related to the strength of the stimulating current, and the amount of LH-RF liberated diminished on cessation of the stimulus. The concentration of LH-RF in pituitary stalk plasma from female rats was significantly greater than that in jugular venous plasma. The magnitudes of the mean increments of LH-RF in pituitary stalk plasma (stimulation minus pre-stimulation values) at various times of the oestrous cycle in female rats suggests that between 18.00 h of dioestrus and 13.00 h of pro-oestrus there is an increase in sensitivity of the LH-RF secretory mechanism to electrical stimulation. However, the increments decreased in magnitude between 13.00 and 18.00 h of pro-oestrus, indicating that the marked increase in responsiveness of the hypothalamo-hypophysial system to electrical stimulation which occurs during this period is due mainly to a change in sensitivity of the pituitary gonadotrophs to LH-RF. The LH-RF in pituitary stalk plasma collected before application of the stimulus was higher at some of the times examined during pro-oestrus than at other times of the oestrous cycle. A higher level of the secretion of the factor may be important for the full development of the priming effect of LH-RF and, consequently, the marked increase in responsiveness of the pituitary gland which occurs during the afternoon of pro-oestrus.

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.

GONADOTROPHIN SECRETION AFTER ELECTRICAL STIMULATION OF THE PREOPTIC AREA DURING THE OESTROUS CYCLE OF THE RAT

1974 ◽  
Vol 62 (3) ◽  
pp. 589-604 ◽  
Author(s):  
G. FINK ◽  
M. S. AIYER
Keyword(s):  
Electrical Stimulation ◽  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Preoptic Area ◽  
Medial Preoptic Area ◽  
Anterior Pituitary Gland ◽  
Oestrous Cycle ◽  
Early Afternoon ◽  
Stimulation Of

SUMMARY The responsiveness of the hypothalamo-hypophysial axis to electrical stimulation of the medial preoptic area was tested at various times during the oestrous cycle of the rat. Animals were anaesthetized with sodium pentobarbitone, and glass-insulated bipolar platinum electrodes were stereotaxically implanted in the medial preoptic area. The stimulus consisted of accurately balanced biphasic rectangular pulses, height 500 μA, duration 2 ms and frequency 60 Hz, applied in trains of 30 s intervals. The concentration of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in blood samples withdrawn from the external jugular vein immediately before and at frequent intervals up to 1 h after application of the stimulus was determined by radioimmunoassay. In all animals the stimulus was applied for a period of 15 min, for it was found that under these conditions the profiles of LH and FSH produced in individual animals were similar to those which followed the i.v. injection of 50 ng synthetic luteinizing hormone releasing factor (LH-RF)/100 g body wt, the minimal ovulatory dose of LH-RF in our laboratory. Both for LH and FSH, the profiles of responsiveness of the hypothalamo-hypophysial axis to electrical stimulation through the oestrous cycle resembled closely the profile of responsiveness of the anterior pituitary gland to LH-RF administered intravenously. There was a relatively gradual increase in pituitary sensitivity, in terms of the mean maximal increments, between the early afternoon of dioestrus and pro-oestrus, followed by an abrupt and marked rise which reached a peak at 18.00 and 21.00 h of pro-oestrus for LH and FSH, respectively. Sensitivity of the hypothalamo-hypophysial axis declined through oestrus and metoestrus reaching a nadir at 13.30 h of dioestrus. While these results do not exclude a change in sensitivity of the neural component of the hypothalamo-hypophysial axis during the oestrus cycle, they do indicate that the timing and magnitude of changes in sensitivity of the anterior pituitary gland to both endogenous and exogenous LH-RF are similar. This raises the possibility that a marked increase in the secretion of LH-RF during the afternoon of pro-oestrus may not be necessary for the occurrence of the surge of LH and FSH, for conceivably the latter could depend on a change in sensitivity of pituitary gonadotrophs to constant or only slightly increased levels of LH-RF in hypophysial portal blood. Our findings are compared with those of workers who have employed electrochemical stimulation of the preoptic area.

scholarly journals Heart reaction of male and female with streptozotocin induced diabetes on cholinergic impacts

2020 ◽  
Vol 73 (2) ◽  
pp. 224-228
Author(s):  
Orysia O. Bandrivska ◽  
Vitalij M. Mykhailiuk ◽  
Iryna A. Mykhailiuk ◽  
Natalia V. Malko
Keyword(s):  
Vagus Nerve ◽  
Sinus Node ◽  
Female Rats ◽  
Chronotropic Effect ◽  
Maximum Increase ◽  
Male And Female ◽  
Negative Chronotropic Effect ◽  
Male And Female Rats ◽  
Streptozotocin Induced Diabetes ◽  
Stimulation Of

The aim: Find out the nature of the changes sensitivity of the heart to the cholinergic influences the development of diabetes depending on gender. Materials and methods: In experiments on adult male and female rats, type 1 diabetes by momentary introduction of streptozotocin at a dose of 60 mg/ kg into the peritoneal cavity was modeled. Animals were examined after 15, 30, 60 and 90 days after introduction of streptozotocin. We studied the sensitivity of cholinoreceptors of sinus node by the intensity of bradycardia with intravenous injection of acetylcholine and electrical stimulation of the peripheral segment of the right vagus nerve. Results: It was established that the intensity of the negative chronotropic effect of heart of males by electric stimulation of the vagus nerve, which depends on the reserves of acetylcholine in the presynaptic section and sensitivity of postsynaptic cholinoreceptors, increased gradually and after 90 days prevailed the output value in 2.2 times. This occurred at the background of a slight (10 %) decrease in response to exogenous acetylcholine that reflected the decrease in sensitivity of cholinoreceptors. In females the maximum increase (in 4.4 times) of the intensity of the negative chronotropic effect of vagus nerve stimulation was observed after 30 days from the start of the experiment. After 90 days, this indicator prevailed the controlled one in 3.3 times, which occurred at the background of heart response decreasing to exogenous acetylcholine (in 1.7 times). Conclusions: Obtained results suggest a more significant change in state of cholinoceptor system of myocardium of females compared with males in the dynamics of development of streptozotocin-induced diabetes.

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