scholarly journals Extracellular K+ in the supraoptic nucleus of the rat during reflex bursting activity by oxytocin neurones.

1991 ◽  
Vol 439 (1) ◽  
pp. 383-409 ◽  
Author(s):  
J A Coles ◽  
D A Poulain
Keyword(s):  
Supraoptic Nucleus ◽  
Bursting Activity ◽  
Oxytocin Neurones

Effect of progesterone on the activation of neurones of the supraoptic nucleus during parturition

Reproduction ◽  
2000 ◽  
pp. 367-376 ◽  
Author(s):  
IA Antonijevic ◽  
JA Russell ◽  
RJ Bicknell ◽  
G Leng ◽  
AJ Douglas
Keyword(s):  
Progesterone Receptor ◽  
Supraoptic Nucleus ◽  
Late Pregnancy ◽  
Endogenous Opioids ◽  
Opioid Antagonist ◽  
Endogenous Opioid ◽  
Fos Expression ◽  
Oxytocin Neurones ◽  
Supraoptic Nuclei

Parturition is driven by a pulsatile pattern of oxytocin secretion, resulting from burst firing activity of supraoptic oxytocin neurones and reflected by induction of Fos expression. Rats were injected with progesterone on day 20 of pregnancy to investigate the role of the decreasing progesterone:ratio oestrogen ratio, which precedes delivery, in the activation of supraoptic neurones. Progesterone delayed the onset of birth by 28 h compared with vehicle (control) and prolonged the duration of delivery, which was overcome by pulsatile injections of oxytocin, indicating that the slow delivery may reflect impaired oxytocin secretion. Parturient rats pretreated with progesterone had fewer Fos immunoreactive nuclei in the supraoptic nucleus than did parturient rats pretreated with vehicle. The number of Fos immunoreactive nuclei was not restored after oxytocin injection, indicating that appropriate activation of oxytocin neurones is impaired by progesterone and also that there is a lack of stimulatory afferent drive. Fos expression increased in the nucleus of the tractus solitarius during parturition in rats pretreated with either vehicle or progesterone, but not in rats that had been pretreated with progesterone and induced with oxytocin, indicating that this input was inhibited. Endogenous opioids inhibit oxytocin neurones in late pregnancy and the opioid antagonist, naloxone, increases Fos expression in supraoptic nuclei by preventing inhibition. However, progesterone attenuated naloxone-induced Fos expression in the supraoptic nucleus in late pregnancy and naloxone administered during parturition did not accelerate the duration of births delayed by progesterone administration, indicating that progesterone does not act by hyperactivation of endogenous opioid tone. RU486, a progesterone receptor antagonist, enhanced supraoptic neurone Fos expression in late pregnancy, indicating progesterone receptor-mediated actions. Thus, progesterone withdrawal is necessary for appropriate activation of supraoptic and tractus solitarius neurones during parturition.

Relaxin increases the firing rate of supraoptic neurones and increases oxytocin secretion in the rat

1992 ◽  
Vol 132 (1) ◽  
pp. 149-158 ◽  
Author(s):  
S. A. Way ◽  
G. Leng
Keyword(s):  
Electrical Activity ◽  
Firing Rate ◽  
Supraoptic Nucleus ◽  
Ovariectomized Rats ◽  
Milk Ejection ◽  
Independent Mechanism ◽  
Stimulus Secretion Coupling ◽  
Milk Ejection Reflex ◽  
Oxytocin Neurones ◽  
Sustained Increase

ABSTRACT In urethane-anaesthetized ovariectomized rats, injection of porcine relaxin (7·5 and 15 μg/kg, i.v.) caused a sustained increase in circulating plasma oxytocin and vasopressin concentrations; 10 μg relaxin/rat i.v. produced a smaller but significant increase in plasma oxytocin concentration in conscious ovariectomized rats. A significant increase in oxytocin concentration and inhibition of the spontaneous milk-ejection reflex was also seen in anaesthetized (ovary intact) lactating rats following injection of relaxin (7·5 μg/kg, i.v.). To investigate whether relaxin acts by increasing the electrical activity of oxytocin neurones or by facilitating stimulus-secretion coupling in the pituitary, the electrical activity of neurones in the supraoptic nucleus was recorded in urethane-anaesthetized lactating rats and in ovariectomized rats. Porcine relaxin (10 μg/rat, i.v.) increased the firing rate of both oxytocin and vasopressin neurones in the supraoptic nucleus in lactating rats. The response to relaxin was unaffected by subsequent injection of naloxone (1 mg/kg, i.v.). Oxytocin neurones were also activated by injection of relaxin (10 μg/rat) into ovariectomized rats. Combining the electrophysiological data, the neuronal activation following relaxin was significantly correlated with the level of spontaneous activity prior to relaxin injection. The results show that relaxin acts centrally to increase circulating plasma oxytocin and vasopressin concentrations by an opioid-independent mechanism. Journal of Endocrinology (1992) 132, 149–158

scholarly journals Local opioid inhibition and morphine dependence of supraoptic nucleus oxytocin neurones in the ratin vivo

1997 ◽  
Vol 505 (1) ◽  
pp. 145-152 ◽  
Author(s):  
Mike Ludwig ◽  
Colin H. Brown ◽  
John A. Russell ◽  
Gareth Leng
Keyword(s):  
Supraoptic Nucleus ◽  
Morphine Dependence ◽  
Oxytocin Neurones

scholarly journals Physiology of spontaneous [Ca2+]i oscillations in the isolated vasopressin and oxytocin neurones of the rat supraoptic nucleus

Cell Calcium ◽  
2016 ◽  
Vol 59 (6) ◽  
pp. 280-288 ◽  
Author(s):  
Stepan Kortus ◽  
Chinnapaiyan Srinivasan ◽  
Oksana Forostyak ◽  
Yoichi Ueta ◽  
Eva Sykova ◽  
...  
Keyword(s):  
Supraoptic Nucleus ◽  
Oxytocin Neurones
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