Cerebrospinal Fluid Oxytocin Research Articles

Pulses of oxytocin in the cerebrospinal fluid of rhesus monkeys.

Cerebrospinal fluid (CSF) samples were collected at frequent intervals (every 10-15 min) to determine if oxytocin pulses were present in the CSF of monkeys. Temporary indwelling subarachnoid catheters, with the tip of the catheter at the T12-L1 subarachnoid space, were placed in 4 nonlactating and 3 lactating (4 months post partum) female monkeys. Monkeys were maintained on jacket/tether/swivel systems in a constant photoperiod (07.00-19.00 h). CSF was continuously withdrawn at a rate of 1.2 ml/h by peristaltic pump, and CSF was collected in 15-min fractions (from 3 lactating monkeys and 1 nonlactating monkey) or in 10-min fractions (from the other 3 nonlactating monkeys) using a fraction collector. CSF oxytocin was measured by radioimmunoassay. Pulses of oxytocin were analyzed using the computerized Pulsar pulse detection algorithm. A pulsatile pattern of oxytocin concentrations was found in the CSF of lactating and nonlactating monkeys. The ultradian pulses of oxytocin were superimposed upon the diurnal rhythm of oxytocin in CSF. We conclude that frequent sampling of CSF provides a way to monitor moment-to-moment changes in central nervous system concentrations of oxytocin in primates.

Release of Oxytocin into Blood and into Cerebrospinal Fluid Induced by Naloxone in Anaesthetized Morphine‐Dependent Rats: The Role of the Paraventricular Nucleus

Abstract Opioid actions on oxytocin secretion into blood and cerebrospinal fluid (CSF) were investigated in urethane-anaesthetized female rats after intracerebroventricular (icv) infusion of morphine sulphate or vehicle for 5 days. Serial femoral arterial blood samples and cisterna magna CSF samples were collected for radioimmunoassay. Naloxone was given to assess endogenous opioid tone in icv vehicle-infused rats and to precipitate withdrawal in morphine-dependent animals. Initial plasma oxytocin concentration was not affected by icv morphine infusion. In control rats receiving icv vehicle, naloxone increased plasma oxytocin 11-fold within 5 min, and in icv morphine-infused rats, naloxone increased plasma oxytocin 80-fold within 5 min. In both groups, 90 min after naloxone plasma oxytocin was still 5 and 10 times, respectively, the initial concentration. Without naloxone, neither plasma nor CSF oxytocin concentration changed significantly with time (up to 90 min) in either icv treatment group. In the icv vehicle group, there was a 2-fold increase in CSF oxytocin 90 min after naloxone. In the icv morphine-infused group, CSF oxytocin was increased 5-fold 40 min after naloxone. In another group of icv morphine-infused rats, intravenous infusion of oxytocin to achieve plasma levels similar to those seen after naloxone, did not significantly increase CSF oxytocin. In a further group of icv morphine-infused rats, [(3)H]oxytocin was infused intravenously immediately after naloxone was given; in these rats oxytocin transfer from blood to CSF could account at most for only 20% of the increase in CSF oxytocin after naloxone. A further group of rats underwent bilateral microknife ablation of the paraventricular nuclei (PVN) 9 days before icv vehicle or morphine infusions were started; blood and CSF samples were collected under urethane anaesthesia. Initial concentrations of oxytocin in CSF and in plasma were similar in both groups with PVN ablation. In all PVN-lesioned rats initial plasma concentrations of oxytocin were undetectable (<5 pg/ml) and thus less than in intact rats. In contrast, initial levels of oxytocin in CSF were 8-fold greater in PVN-lesioned rats than in intact animals. Naloxone increased plasma oxytocin concentration in the icv vehicle group at least 10-fold within 30 min and in the icv morphine group at least 100-fold within 5 min. CSF oxytocin in the icv vehicle group was not altered by naloxone, but in the icv morphine group CSF oxytocin was increased 5-fold 40 min after naloxone. There were no consistent differences between the icv vehicle- and icv morphine-treated groups in the initial plasma levels of vasopressin, growth hormone and adrenocorticotrophin; PVN ablation did not affect adrenocorticotrophin levels. After naloxone growth hormone levels did not change, vasopressin concentration rose moderately only after 90 min and only in the icv vehicle-treated group, and adrenocorticotrophin concentrations decreased with time whether or not naloxone was given. The results imply an endogenous opioid tone on neurons releasing oxytocin into CSF, and morphine-dependence of these neurons. Furthermore, in PVN-lesioned rats, magnocellular supraoptic neurons could be a source of oxytocin release into CSF.

Cerebrospinal fluid and plasma concentrations of oxytocin and vasopressin during parturition and vaginocervical stimulation in the sheep

Simultaneous blood and Cerebrospinal fluid (CSF) samples were taken from conscious sheep before, during and after parturition. Concentrations of plasma and CSF oxytocin were significantly elevated during contractions and particularly at birth. Mean prepartum CSF concentrations of oxytocin were around 55% of those found in plasma but postpartum they were up to 2-fold higher than those in plasma. Plasma concentrations of oxytocin were only significantly elevated, compared to prepartum levels, for 15 min postpartum whereas those in CSF were increased for the whole of the 120 min postpartum sampling period. Plasma, but not CSF, concentrations of arginine-vasopressin (AVP) were significantly raised during contractions and birth, and for 15 min postpartum. During the prepartum period CSF AVP concentrations were 67% of those found in plasma whereas at birth plasma levels were 10-fold higher than in CSF. In a separate experiment it was shown that 5 min of mechanical vaginocervical stimulation also stimulated significant increases in CSF and plasma oxytocin concentrations and in plasma vasopressin. Results support previous work suggesting an important role for central oxytocin release in the postpartum induction of maternal behavior and demonstrate that elevated concentrations of oxytocin in the CSF are present for a greater period than in blood. Elevated plasma AVP concentrations during contractions, birth or vaginocervical stimulation may be stimulated by stress associated with these stimuli.

Pattern of Oxytocin Concentrations in the Plasma and Cerebrospinal Fluid of Lactating Rhesus Monkeys (Macaca mulatto,): Evidence for Functionally Independent Oxytocinergic Pathways in Primates*

Two populations of oxytocin-staining neurons have been identified in the paraventricular nucleus: magnocellular neurons that terminate in the posterior pituitary and parvocellular neurons that terminate elsewhere in the central nervous system. Whether these oxytocin neurons are functionally separate was tested by measuring oxytocin concentrations in samples of peripheral blood and cerebrospinal fluid (CSF) obtained simultaneously from lactating rhesus monkeys during suckling. Lactating animals bearing temporary subarachnoid and venous catheters were maintained in a constant photoperiod (0600-1800 h). Samples of CSF were continuously withdrawn by peristaltic pump (0.1 mL/15 min) for 2-4 consecutive days from subarachnoid catheters with the tips placed at the T12-L1 level of the spinal column in four lactating monkeys 4 months postpartum and again after weaning. On 2 of these days, we observed and recorded periods of infant suckling and collected peripheral blood samples (1.2 mL) from the mother at 5-min intervals for 60 min. Oxytocin was measured in blood and CSF by RIA. Oxytocin concentrations increased in the plasma of the lactating monkeys during periods of nursing, with peak concentrations ranging from 4-16.7 microU/mL. No increase in plasma oxytocin was found on the day after the infant was weaned. Variations in the concentrations of oxytocin in CSF were independent of the suckling stimulus and plasma oxytocin concentrations and occurred during observed periods of no nipple contact by the infant and at the time of weaning after the infant had been removed from the mother. Each lactating animal also displayed a normal circadian variation in CSF oxytocin concentrations, with peak and nadir levels during light and dark hours, respectively. We conclude that release of oxytocin into the CSF of lactating monkeys is disassociated from release into the peripheral circulation. The data further support the conclusion that neuronal pathways giving rise to oxytocin in the CSF and the periphery are anatomically and functionally separate in primates.

Effect of Estradiol and Progesterone Administration upon the Circadian Rhythm of Oxytocin in the Cerebrospinal Fluid of Rhesus Monkeys

The effect of administration of estradiol (E2) alone or combined with progesterone upon the circadian rhythm of oxytocin concentrations in cerebrospinal fluid (CSF) was examined in adult ovariectomized rhesus monkeys bearing temporary subarachnoid catheters and maintained in a constant photoperiod (lights on 06.00-18.00 h). Animals were subcutaneously implanted with silastic capsules containing 17 beta-E2 for 6 days and progesterone for the last 3 days of E2 administration. Hourly samples of CSF were collected before, during and after gonadal steroid administration and measured for oxytocin by RIA and reverse-phase high-performance liquid chromatography (RP-HPLC). A significant increase in the serum concentration of E2 and the plasma concentration of oxytocin neurophysin, but not the plasma concentration of oxytocin, was found during gonadal steroid administration. Each animal displayed a dirunal pattern of secretion of oxytocin in CSF with peak and trough levels during light and dark hours, respectively. No significant differences were found across experimental conditions in the following CSF oxytocin parameters: mean level of oxytocin in CSF during the light, dark, or light and dark hours combined; the daily phase or amplitude of the CSF oxytocin rhythm; the peak or nadir concentration of oxytocin in CSF; or the total amount of oxytocin secreted into the CSF as expressed as the area under the curve (multivariate repeated measures ANOVA). The CSF oxytocin parameters in the animals that were restudied using empty silastic implants were not significantly different across time (multivariate repeated measures ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian Rhythm of Oxytocin in the Cerebrospinal Fluid of Rhesus and Cynomolgus Monkeys: Effects of Castration and Adrenalectomy and Presence of a Caudal-Rostral Gradient

Oxytocin and vasopressin (AVP) were previously reported to have a diurnal rhythm in cerebrospinal fluid (CSF) collected from the cervical cistern of chaired, intact male rhesus monkeys. In the present study, we continuously sampled CSF from temporary indwelling catheters placed in the spinal subarachnoid space of unanesthetized monkeys maintained on tether and swivel systems. CSF was collected from intact and castrate female rhesus monkeys and intact female and castrate, adrenalectomized male cynomolgus monkeys to determine if oxytocin and AVP rhythms are expressed in spinal subarachnoid CSF, if the magnitude of the CSF rhythm displays a rostral-caudal gradient, and if the rhythm is present in adrenalectomized and castrate monkeys, or is specific to the sex or species of macaque. Monkeys, maintained on a 12-hour light/dark cycle with lights on from 06.00 to 18.00 h, had 19-gauge epidural catheters introduced at the L4-L5 intervertebral space and advanced cephalad in the subarachnoid space. The proximal end of the catheter was connected to a peristaltic pump for continuous removal of CSF (0.5 ml/h) and hourly CSF samples were radioimmunoassayed for oxytocin and AVP. For rostral-caudal studies, the distal tip of the catheter was repositioned every few days to collect CSF from 3 levels of the spinal subarachnoid space: C5-6, T5-6, T12-L1. Each animal had a diurnal CSF oxytocin rhythm with peak and trough oxytocin levels during early light and dark periods, respectively. The magnitude of the oxytocin rhythm differed among animals, but was consistent in an animal from day to day.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrospinal fluid neurohypophysial peptides in benign intracranial hypertension.

The cerebrospinal fluid (CSF) concentrations of arginine vasopressin (AVP) and oxytocin (OT) were investigated both in patients with benign intracranial hypertension and in age and sex matched controls. Twenty eight lumbar punctures were performed on 15 patients with benign intracranial hypertension as part of their routine investigation and therapy. All patients had raised intracranial pressure (27.4, SE 1.7 cm.CSF). CSF AVP levels were significantly elevated in benign intracranial hypertension (2.1, SE 0.3 pmol/l) compared with controls (0.7, SE 0.1 pmol/l, p less than 0.001) but CSF OT concentrations were similar in both groups. CSF osmolality and plasma AVP and osmolality were identical in patients and controls. There was no correlation between CSF AVP concentration and intracranial pressure. The selective elevation of AVP in CSF may be of importance in the pathogenesis of raised intracranial pressure in benign intracranial hypertension.

Diurnal rhythm of vasopressin but not of oxytocin in the cerebrospinal fluid of the goat: lack of association with plasma cortisol rhythm.

Diurnal rhythms in the concentrations of vasopressin (AVP) and oxytocin in cerebrospinal fluid (CSF) differ between species and are unrelated to changes in the levels of these hormones in the peripheral circulation. We have investigated neurohypophysial hormone rhythms in the CSF of the conscious goat by determining whether they are entrained by daily cycles of light and darkness and by assessing the effect of the suppression of plasma cortisol. Goats were implanted with cisternal cannulae under halothane anaesthesia and allowed to recover. They were accustomed to a 12 h light:12 h darkness lighting cycle (lights on from 07.30 to 19.30 h). After initial serial CSF and plasma sampling the daily cycle of light and darkness was reversed. Three goats were kept in constant light for 8 days before the study and five were given dexamethasone (5 mg/12 h) for 4 days. There was a significant (P less than 0.01) diurnal variation in CSF concentrations of AVP, with a maximum of 3.6 +/- 0.8 (S.E.M.) pmol/l at 12.00 h and a minimum of 1.4 +/- 0.3 pmol/l at 24.00 h. There were no significant changes in CSF concentrations of oxytocin or plasma AVP. After the light:darkness cycle was reversed the AVP rhythm in the CSF was disrupted after 24 h and reversed after 8 days. The diurnal rhythm of AVP in CSF persisted in animals exposed to constant light. After treatment with dexamethasone plasma cortisol was suppressed and showed no diurnal rhythm but the AVP rhythm in CSF remained unchanged.

Oxytocin in the central nervous system and sexual behaviour in male rats

Concentrations of oxytocin (OT) and vasopressin (AVP) were measured in cerebrospinal fluid (CSF) obtained from the cisterna magna of freely moving rats. Basal levels of OT and AVP were approximately 9 fmol/ml in both male and female. In the male rats this increased to approximately 18 fmol/ml 5 min after ejaculation, and 27 fmol/ml 20 min after ejaculation. No increase from basal levels occured when males were placed with unreceptive females, or alone in the test environment. AVP levels were unchanged in any condition. Preliminary investigations indicate that discrete electrolytic lesions to the lateral and posterior parvocellular hypothalamic paraventricular nucleus (PVN) abolished this ejaculation-associated increase in CSF OT, prolonged mount and intromission latencies and reduced the absolute postejaculatory interval (PEI). We conclude that intracerebrally projecting OT systems may be activated during coitus and may contribute to the mechanisms underlying postejaculatory refractoriness.

Clonidine decreases plasma and cerebrospinal fluid arginine vasopressin but not oxytocin in humans.

To evaluate the alpha 2-noradrenergic regulation of arginine vasopressin (AVP) and oxytocin (OT) in normal humans, we measured the effect of the alpha 2-agonist clonidine on concentrations of these neuropeptides in both plasma and cerebrospinal fluid (CSF). Subjects underwent two lumbar puncture studies, one of which was performed 100 min after oral administration of 5 micrograms/kg clonidine. Plasma AVP and OT were measured at a single time point 10 min before lumbar puncture. Both plasma and CSF AVP were significantly lower in the clonidine condition than in the control (no drug) condition. Neither plasma nor CSF OT differed significantly between conditions. Our data confirm previous reports of alpha 2-noradrenergic inhibition of neurohypophyseal release of AVP into blood, and extend these findings to healthy human subjects. Our data also suggest that AVP appearance in CSF, presumably from extraneurohypophyseal vasopressinergic neurons, is regulated by an inhibitory alpha 2-noradrenergic mechanism.

Neurohypophysial hormones in cerebrospinal fluid of adults: absence of arginine vasotocin and of a diurnal rhythm of arginine vasopressin.

We previously reported a prominent diurnal rhythm of oxytocin (OT) in human cerebrospinal fluid (CSF) similar to the brisk CSF OT rhythm in monkeys. An OT CSF rhythm has not been found in lower species. In contrast, a pronounced arginine vasopressin (AVP) rhythm has been found in lower species, but the AVP CSF rhythm is less marked in subhuman primates. In patients (n = 7) in whom lumbar drains had been temporarily placed for treatment of CSF rhinorrhea, we obtained CSF samples every 6 h. In 6 of these 7 patients, we previously reported (1) finding a prominent CSF OT rhythm, with a peak at 1200 h, by analysis of variance of repeated measures. When the samples of CSF of these same 6 patients (plus 1 additional patient) were assayed for AVP, no AVP rhythm was found. We also measured AVP, OT, and arginine vasotocin (AVT) by RIA in single samples of CSF obtained from 23 other patients. In these single samples of CSF, mean AVP was 0.9 +/- 0.11 (+/- SEM) pg/ml, and OT was 3.7 +/- 0.5 microU/ml. CSF AVT immunoreactivity was 0.6 pg/ml or less in the 23 patients. Two pools of CSF were separated by reverse phase high pressure liquid chromatography. The peak OT and AVP, as determined by RIA, coeluted exactly with synthetic and human posterior pituitary OT and AVP, respectively. No immunoreactive AVT was found in the position of synthetic AVT in the eluates. Thus, OT and AVP are present in human adult CSF, but AVT is not. The lack of a prominent rhythm of AVP in human CSF is in marked contrast to the brisk OT rhythm. The rhythm of neurohypophysial peptides in human and subhuman primates is different from the rhythm in lower species, suggesting different functions for OT and AVP in the central nervous system of various species.

The circadian rhythm of oxytocin in primate cerebrospinal fluid: effects of destruction of the suprachiasmatic nuclei

The effects of lesions of the suprachiasmatic nuclei (SCN) on the circadian rhythm of oxytocin concentrations in cerebrospinal fluid (CSF) were examined in the rhesus monkey. In the two sham-operated animals, the rhythm was normally entrained to the daily lightdark cycle and persisted in constant lighting conditions at both 4 and 8 months after surgery. Similarly, the oxytocin rhythm was clearly manifested in the two animals with complete SCN ablation 4 months after surgery. At 8 months after surgery, however, the daily CSF rhythm was disrupted in one of the lesioned animals, while it persisted in the other animal. The data show that the SCN are not required for the expression of the daily rhythm of CSF oxytocin, suggesting that a circadian system outside the SCN normally generates the oxytocin rhythm.

Penetration of neurohypophyseal hormones from plasma into cerebrospinal fluid (CSF): Half-times of disappearance of these neuropeptides from CSF

The penetration of neurohypophyseal peptides after peripheral administration into the cerebrospinal fluid (CSF) was studied in freely moving rats. In addition, the clearance of these peptides from CSF was investigated. Increased concentrations of vasopressin (AVP) in CSF were detectable 2 min after s.c. injection of 5.0 μg of this peptide. Peak concentration was reached at 5 min after administration and this level declined slowly over the next hour. Administration of 5.0 μg oxytocin (OXT) s.c. or i.v. resulted in increased OXT levels in CSF within 10 min after application. After 60 min a significant elevation of OXT in CSF was no longer present. These data reveal that approximately 0.002% of the peripherally applied amount of AVP or OXT reached the central nervous system at 10 min after injection. AVP (2.5 ng) and OXT (5.0 ng) applied into one of the lateral brain ventricles reached the cisternal cavity within 2 min after administration. Both neuropeptides were cleared from the CSF with terminal half-times of 26 and 19 min for AVP and OXT, respectively. The present data demonstrate that neurohypophyseal hormones do cross the blood-brain barrier in amounts obviously sufficient to induce central actions.

Comparison of the temporal profiles of vasopressin and oxytocin in the cerebrospinal fluid of the cat, monkey and rat

The temporal profiles of oxytocin were examined in the cerebrospinal fluid (CSF) of the cat and rat. Unlike the marked daily rhythm of oxytocin concentrations recently described in the CSF of the rhesus monkey, no daily rhythm of the peptide was evident in the CSF of either the cat or rat. The apparent species specificity of the CSF oxytocin profiles among these mammals is contrasted with the consistent expression of a daily rhythm of arginine-vasopressin in the CSF of each of the three species.

Characterization of the daily oxytocin rhythm in primate cerebrospinal fluid

The circadian characteristics of the daily rhythm in oxytocin (OT) concentrations in cerebrospinal fluid (CSF) were studied in the rhesus monkey. Monkeys subjected to constant light or constant dark for periods of 3 to 6 days manifested persistence of the CSF OT rhythm. A 12-hr phase shift in the light-dark cycle resulted in a resynchronization of the rhythm to the new lighting schedule within 3 to 4 days. Altering the daily feeding and care schedule during a period of constant darkness did not alter the expression or timing of the CSF OT rhythm significantly. These results suggest that the OT rhythm is endogenously generated and that the daily light-dark cycle normally synchronizes the rhythm to the 24-hr cycle.

Oxytocin and neurophysin in plasma and CSF during suckling in the guinea-pig.

Cerebrospinal fluid (CSF) obtained from the cisterna magna of conscious unrestrained guinea-pigs was assayed for oxytocin (OT), vasopressin (AVP) and neurophysin (NP). Basal levels of OT and AVP were approximately 5 and 15 fmol/ml, respectively, whereas NP levels were considerably higher (around 1 pmol/ml); there was no significant differences between males, females and lactating females. In lactating females, simultaneous samples of blood and CSF were obtained during suckling episodes. Despite large increases in plasma OT and NP at milk ejection, CSF levels remained unchanged throughout. Intracerebroventricular injection of 100 fmol OT produced an 8-fold rise in the concentration of this peptide in cisternal fluid within 10 min. Since CSF levels of OT and NP do not change when these peptides are released from the pituitary, we conclude that the presence of these peptides in CSF reflects activity of extrapituitary terminals and that these terminals are not activated during suckling.

Evidence for the release of vasopressin and oxytocin into cerebrospinal fluid: measurements in plasma and CSF of intact and hypophysectomized rats.

Arginine-8-vasopressin (AVP) and oxytocin (OXT) were measured by radio-immunoassay (RIA) in cerebrospinal fluid (CSF) and plasma of Wistar rats under various conditions. In addition, basal plasma levels of OXT were measured in Brattleboro rats, either homozygous or heterozygous for diabetes insipidus (Ho-DI or He-DI respectively). The basal OXT plasma level of Ho-DI rats was elevated as compared to He-DI and Wistar rats. Water deprivation caused a gradual increase of plasma OXT levels in Wistar rats. CSF was collected from Wistar rats by withdrawal from the cisterna magna under pentobarbitone anesthesia. Anesthesia induced a rise of the plasma AVP level as well as of the plasma OXT level. Withdrawal of CSF caused a dramatic rise of plasma AVP levels and, to a minor extent, of plasma OXT levels. In rats studied at 4 weeks after hypophysectomy plasma AVP levels were only detectable after CSF withdrawal. CSF levels of AVP were elevated in these animals. In intact and hypophysectomized rats, basal OXT plasma levels and the increased levels after anesthesia were the same. The OXT release into the blood was partly impaired after hypophysectomy because CSF withdrawal did not result in a further rise of plasma OXT levels. CSF oxytocin levels were the same in intact and hypophysectomized rats. A difference of the effect of hypophysectomy was thus observed with respect to the presence in CSF and plasma for AVP but not for OXT. It is concluded that the regeneration of AVP and OXT fibers is different which leads to a different release of the hormones into CSF and plasma.