Estrogen receptor ß and oxytocin interact to modulate anxiety-like behavior and neuroendocrine stress reactivity in adult male and female rats.

The hypothalamic-pituitary-adrenal (HPA) axis is activated in response to stressors and is controlled by neurons residing in the paraventricular nucleus of the hypothalamus (PVN). Although gonadal steroid hormones can influence HPA reactivity to stressors, the exact mechanism of action is not fully understood. It is known, however, that estrogen receptor ß (ERß) inhibits HPA reactivity and decreases anxiety-like behavior in rodents. Since ERß is co-expressed with oxytocin (OT) in neurons of the PVN, an ERß-selective agonist was utilized to test the whether ERß decreases stress-induced HPA reactivity and anxiety-like behaviors via an OTergic pathway. Adult gonadectomized male and female rats were administered diarylpropionitrile, or vehicle, peripherally for 5days. When tested for anxiety-like behavior on the elevated plus maze (EPM), diarylpropionitrile-treated males and females significantly increased time on the open arm of the EPM compared to vehicle controls indicating that ERß reduces anxiety-like behaviors. One week after behavioral evaluation, rats were subjected to a 20minute restraint stress. Treatment with diarylpropionitrile reduced CORT and ACTH responses in both males and females. Subsequently, another group of animals was implanted with cannulae directed at the lateral ventricle. One week later, rats underwent the same protocol as above but with the additional treatment of intracerebroventricular infusion with an OT antagonist (des Gly-NH2 d(CH2)5 [Tyr(Me)(2), Thr(4)] OVT) or VEH, 20min prior to behavioral evaluation. OT antagonist treatment blocked the effects of diarylpropionitrile on the display of anxiety-like behaviors and plasma CORT levels. These data indicate that ERß and OT interact to modulate the HPA reactivity and the display of anxiety-like behaviors.

Yes, I am ready now: differential effects of paced versus unpaced mating on anxiety and central oxytocin release in female rats.

Sexual activity and partner intimacy results in several positive consequences in the context of stress-coping, both in males and females, such as reduced state anxiety in male rats after successful mating. However, in female rats, mating is a rewarding experience only when the estrous female is able to control sexual interactions, i.e., under paced-mating conditions. Here, we demonstrate that sex-steroid priming required for female mating is anxiolytic; subsequent sexual activity under paced mating conditions did not disrupt this anxiolytic priming effect, whereas mating under unpaced conditions increased anxiety-related behavior. In primed females, the release of the neuropeptide oxytocin (OT) within the hypothalamic paraventricular nucleus was found to be elevated and to further increase during paced, but not unpaced mating. Central administration of an OT receptor antagonist partly prevented priming/mating-induced anxiolysis indicating the involvement of brain OT in the anxiolysis triggered by priming and/or sexual activity.These findings reveal that the positive consequences of mating in females are dependent on her ability to control sexual interactions, and that brain OT release is at least in part the underlying neurobiological correlate.

Central oxytocin modulation of acute stress-induced cardiovascular responses after myocardial infarction in the rat.

The present study was aimed at determining the role of centrally released oxytocin in regulation of blood pressure and heart rate (HR) under resting conditions and during an acute air-jet stress in rats with a myocardial infarction and controls infarcted. Four weeks after ligation of a coronary artery or sham surgery, conscious Sprague Dawley rats were subjected to one of the following intracerebroventricular (ICV) infusions: (1) 0.9% NaCl (control), (2) oxytocin, (3) oxytocin receptor antagonist {desGly-NH(2)-d(CH(2))(5)[D-Tyr(2)Thr(4)]OVT}(OXYANT). Resting arterial blood pressure and HR were not affected by any of the ICV infusions either in the infarcted or sham-operated rats. In the control experiments, the pressor and tachycardic responses to the air jet of infarcted rats were significantly greater than in the sham-operated rats. OXYANT significantly enhanced the cardiovascular responses to stress only in the sham-operated rats whereas oxytocin significantly attenuated both responses in the infarcted but not in the sham-operated rats. The results suggest that centrally released endogenous oxytocin significantly reduces the cardiovascular responses to the acute stressor in control rats. This buffering function of the brain-oxytocin system is not efficient during the post-myocardial infarction state, however it may be restored by central administration of exogenous oxytocin.

Antagonism of oxytocin prevents suckling- and estradiol-induced, but not progesterone-induced, secretion of prolactin.

In female rats, estradiol (E(2)) and suckling induce prolactin (PRL) secretion. This involves inhibition of hypothalamic dopaminergic tone and stimulation by a PRL-releasing hormone, possibly oxytocin (OT). Infusing an OT antagonist (OTA) i.v., we evaluated the role of OT on suckling- and E(2)-induced PRL secretion. Three days after parturition at 0900 h, lactating dams were fitted with 24-h osmotic minipumps filled with saline or OTA. On d 5 of lactation, pups were separated from their dams for 6 h. Immediately or 20 min after the resumption of suckling, dam trunk blood was collected. Also, ovariectomized (OVX) rats were treated with E(2) (OVE) and OTA at 1000 h on d 1. Blood samples were obtained from 1300 to 2100 h on d 2 for PRL measurements. Additionally, OVX rats were evaluated on d 2 after receiving progesterone (P(4)). OTA blocked suckling and E(2)-induced release of PRL but not that induced by E(2)+P(4). Pups from treated dams failed to gain weight when allowed to nurse for 20 min on d 5 but gained more than 7 g when nursed on d 7 of lactation, indicating that the OTA was active 48 h later. Western blot analysis showed that E(2) treatment increased OT receptors in the anterior pituitary when compared with OVX animals. No further increase was observed in response to the P(4), suggesting that the enhancing effect of P(4) on E(2)-induced PRL release may act through mechanisms independent of OT. These data demonstrate the role of OT in the control of suckling and steroid-induced PRL secretion.

Oxytocin action at the lactotroph is required for prolactin surges in cervically stimulated ovariectomized rats.

Cervical stimulation induces two daily rhythmic prolactin surges, nocturnal and diurnal, which persist for several days. We have shown that a bolus injection of oxytocin initiates a similar prolactin rhythm, which persists despite low levels of oxytocin after injection. This suggests that oxytocin may trigger the cervical stimulation-induced rhythmic prolactin surges. To investigate this hypothesis, we infused an oxytocin antagonist that does not cross the blood-brain barrier for 24 h before and after cervical stimulation and measured serum prolactin. We also measured dopaminergic neuronal activity because mathematical modeling predicted that this activity would be low in the presence of the oxytocin antagonist. We thus tested this hypothesis by measuring dopaminergic neuronal activity in the tuberoinfundibular, periventricular hypophyseal, and tuberohypophyseal dopaminergic neurons. Infusion of oxytocin antagonist before cervical stimulation abolished prolactin surges, and infusion of oxytocin antagonist after cervical stimulation abolished the diurnal and significantly decreased the nocturnal surges of prolactin. The rhythmic prolactin surges returned after the clearance of the oxytocin antagonist. Hypothalamic dopaminergic activity was elevated in antiphase with prolactin surges, and the antiphase elevation was abolished by the oxytocin antagonist in the tuberoinfundibular and tuberohypophyseal dopaminergic neurons, consistent with the mathematical model. These findings suggest that oxytocin is a physiologically relevant prolactin-releasing factor. However, the cervical stimulation-induced prolactin surges are maintained even in the absence of oxytocin actions at the lactotroph, which strongly suggests the maintenance of prolactin surges are not dependent upon oxytocin actions at the pituitary gland.

Hemodynamic effects of endobronchial application of ornipressin versus terlipressin.

BACKGROUND: Ornipressin and terlipressin, two ADH-derivates, are instilled endobronchially for bronchoscopy- related bleeding without sufficient evidence of efficacy, nor safety. OBJECTIVES: To compare the immediate hemodynamic effects of ornipressin and terlipressin used for procedure-related bleeding during flexible bronchoscopy. METHODS: This retrospective study included patients referred for flexible bronchoscopy who needed administration of ornipressin (15 patients) or terlipressin (15 patients) for procedure-related bleeding. Endobronchial ornipressin (5 IU) or terlipressin (0.5 mg) was administered through the bronchoscope when bleeding persisted for 2 min of continuous suction, or when bleeding was considered increasing in time or major. Hemodynamic data were collected before, during and after administration of either drug. RESULTS: Biopsy-associated hemoptysis requiring medical treatment occurred in 110 (4.2%) of 2,592 bronchoscopies. After administration of ornipressin, no significant change in heart rate or blood pressure was observed. Following terlipressin instillation, heart rate increased from 93 +/- 17 to 101 +/- 22 b.p.m. (p = 0.03), and blood pressure decreased from 107 +/- 14 to 101 +/- 17 mm Hg (p = 0.04). Oxygen saturation under supplemental nasal oxygen was not different in both groups. None of the 110 patients died from bronchoscopy-related hemoptysis or needed further intervention to stop bleeding or prolonged monitoring because of hemodynamic instability. CONCLUSIONS: In contrast to ornipressin, administration of terlipressin is associated with significant changes in heart rate and blood pressure. However, these changes are of minor clinical importance, and terlipressin can be safely given for bronchoscopy-associated bleeding.

Raloxifene lowers ischaemia susceptibility by increasing nitric oxide generation in the heart of ovariectomized rats in vivo.

We studied the effects of a 2-week period of oral raloxifene therapy on the cardiac level of nitric oxide (NO) and on the susceptibility to angina in ovariectomized rats. Ovariectomy decreased the activity of Ca2+-dependent nitric oxide synthase (NOS) in the left ventricle, an effect restored by raloxifene (0.2-5 mg kg(-1) day(-1)) or 17beta-oestradiol (0.3 mg kg(-1) day(-1)). Ovariectomy led to a significant ST segment depression after the injection of (1) ornithine-vasopressin (0.5 IU kg(-1), i.v.) or (2) epinephrine (10 microg kg(-1), i.v.), followed 30 s later by phentolamine (15 mg kg(-1), i.v.); both effects were reversed by raloxifene or 17beta-oestradiol treatment. Inhibition of nitric oxide synthase (with NG-nitro-L-arginine methyl ester [L-NAME]; 5 mg kg(-1), s.c.) augmented the ST segment depression in the ovariectomized rat and abolished the anti-ischaemic effect of 17beta-oestradiol or raloxifene. Thus, an oestrogen deficiency down-regulates the cardiac constitutive nitric oxide synthase, which increases the susceptibility of the heart to ishaemia because both actions can be blocked by exogenous administration of the natural oestrogen 17beta-oestradiol or the selective oestrogen-receptor modulator (SERM) raloxifene. In the present in vivo system, raloxifene exerts oestrogen-agonist properties.

Effects of central oxytocin receptor blockade on water and saline intake, mean arterial pressure, and c-Fos expression in rats.

Central injection of ANG II has been proposed to have dual effects on salt appetite including a direct stimulatory effect and an indirect inhibitory effect through an activation of central oxytocinergic neurons. The inhibition was demonstrated by pretreating rats with central ornithine vasotocin (OVT; oxytocin antagonist) 30 min before a central ANG II injection. The OVT pretreatment produced a large increase in ANG II-induced saline intake. The present paper reports a failure to replicate that influential experiment. However, we also report for the first time that OVT by itself: 1) provokes drinking of both water and saline solution with a latency almost as short as that produced by ANG II; 2) produces a mild pressor response; and 3) increases c-Fos expression in the organum vasculosum laminae terminalis (OVLT) and the median preoptic nucleus (MnPO). Oxytocin activity may provide an inhibitory control of drinking responses as has been suggested, but the inhibition is tonic and includes both water and saline drinking. Inhibition of this tonic activity may stimulate drinking by increasing neural activity in the OVLT and MnPO.

Oxytocin maintains as well as initiates female sexual behavior: effects of a highly selective oxytocin antagonist.

In previous studies, central administration of the oxytocin (OT) antagonist d(CH2)5[Tyr(Me)2, Thr4, Tyr-NH(9)2]OVT (OTA1) blocked receptive and proceptive components of female sexual behavior (FSB) and increased male-directed agonistic behavior when given before progesterone (P) treatment in estradiol-primed female rats but not when given shortly before behavioral testing 4-6 h after P. Because the considerable V(1a) antagonist potency of OTA1 may have contributed to these results, we tested the effects of the far more selective OT antagonist desGly-NH2, d(CH2)5[d-Tyr2, Thr4]OVT (OTA2). In ovariectomized, estradiol benzoate-primed (1 microg x 2 days sc) rats, icv infusion of OTA2 (1 microg) prior to P injection (250 microg sc) significantly suppressed lordosis and hops and darts and trended toward significantly increasing male-directed kicks during testing at 4 and 6 h. Infusion of OTA2 3 h and 40 min after P did not alter behavior at 4 and 6 h after P but significantly decreased lordosis as well as hops and darts and increased male-directed kicks 8-12 h after P. These results provide further evidence that central OT receptor activation shortly after P treatment contributes to the subsequent onset and early expression of FSB and demonstrate, for the first time, that OT receptor activation at later time points also contributes to maintaining FSB. The FSB-stimulating effect of central OT appears to persist for several hours.

Vasoconstrictors during pregnancy--in vitro trial on pregnant and nonpregnant mouse uterus.

In an in vitro trial on 80 pregnant and nonpregnant mice, the sensitivity of the uterus myometrium to the vasoconstrictors vasopressin, ornipressin, epinephrine, and norepinephrine was examined in comparison with oxytocin as a standardized stimulative drug. The pregnant uterus showed a significantly increased sensitivity to ornipressin, vasopressin, and norepinephrine. Epinephrine showed no uterus-stimulating effect, and an increase of sensitivity caused by pregnancy was not detected.

Plasma prilocaine and mepivacaine concentrations after combined lumbosacral plexus block.

In a pharmacokinetic study of combined sciatic/3-in-1 block for lower limb surgery, the two moderate-acting local anaesthetics prilocaine and mepivacaine were compared. The mean maximum venous plasma concentrations of mepivacaine were more than twice as high as when prilocaine was used as anaesthetic (5.1 micrograms/ml vs. 2.37 micrograms/ml). When used in combination with the former, ornipressin did not reduce plasma concentrations of mepivacaine to values which were below the threshold for toxic symptoms (5-6 mg/ml). The peak plasma concentrations exceeded the threshold of 5 micrograms/ml in four of the nine patients of the mepivacaine group (maximum value 7.21 mg/ml) and in two of the nine patients of the mepivacaine+ornipressin group (maximum value 8.61 micrograms/ml).

Animal test or chromatography? Validated high-performance liquid chromatographic assay as an alternative to the biological assay for ornipressin.

Ornipressin is a peptide drug which is usually assayed by a test on live rats. In order to reduce the animal experiments an alternative method was developed which uses gradient high-performance liquid chromatography (HPLC) on reversed-phase. The HPLC method was validated and shown to be selective and precise. Correlation studies were performed on samples of different dosage strengths and on thermally degraded samples, showing good correlation with the results obtained by the biological assay. The HPLC method was applied on various batches of ornipressin in bulk and in pharmaceutical preparations. HPLC is a rapid and inexpensive method which can replace the animal assay. A new quality control concept is proposed which uses HPLC for the analysis of ornipressin in bulk and in pharmaceutical preparations. With this concept animal testing can be reduced by 90%.

[Use of etilefrin as local vasoconstrictor in lower gynecologic surgery ]. / Utilisation de l'étiléfrine comme vasoconstricteur local dans la chirurgie gynécologique par voie basse.

In this randomized prospective study the authors have compared the effectiveness and side-effects of two local vasoconstrictor agents, etilefrine (Effortil) and ornithine 8 vasopressin (Por 8) in vaginal gynaecological surgery. Thirty-three patients entered the trial and were divided into two groups: G1 (15 patients) received Effortil, and G2 (18 patients) received Por 8. The products, administered at random, were diluted in saline 40 ml and injected into the cervix through 6 points. A 3-minute interval was allowed between injection and incision. The results were assessed on the basis of trans- and postoperative haemorrhage and haemodynamic variations. Palor of the cervix was achieved after 3 minutes in both groups; moderate bleeding was observed in only one of the G1 patients. Postoperative renewal of packing was necessary in 2 patients in G1 and 4 patients in G2. No electrocardiographic anomaly was recorded in any of the two groups. Diastolic BP was significantly higher in G2 than in G1 (P less than 0.002, Fisher test). Systolic BP was also elevated in that group (P less than 0.03, chi 2 test). Moderate reduction in heart rate was observed in both groups (P less than 0.3, Fischer test), but severe (48 beats/min) bradycardia was noted in one G2 patient.

[Peridural anesthesia with etidocaine. Clinical studies on the effect of vasoconstrictors on sensory and motor blockade]. / Periduralanaesthesie mit Etidocain. Klinische Untersuchungen zum Einfluss von Vasokonstriktoren auf die sensible und motorische Blockade.

In a randomized double-blind study etidocaine 1.5% without a vasoconstrictor (n = 10), with adrenaline 1:200,000 (n = 10) and with ornipressine 1 IU/10 ml (n = 10) were administered epidurally to 30 orthopaedic patients. Sensory blockade was tested with electric pain stimuli; motor blockade was assessed with dynamometry during isometric plantar flexion of the foot and with the Bromage score; the intraoperative analgesia was determined as well. The development of sensory and motor blockade became faster and more intensive by addition of the two vasoconstrictors. The intraoperative analgesia, insufficient without vasoconstrictors, however, not to full satisfaction. Adrenaline improved the effects of etidocaine more than did ornipressine . The sole use of etidocaine without and with vasoconstrictors is not recommended for epidural anaesthesia for surgery of the lower extremities. It is the local anaesthetic of choice for intensifying motor blockade during already achieved analgesia.

[POR 8 (ornipressin). Local vasoconstrictive effect and hemodynamic activity during surgery in ENT clinics]. / POR 8 (Ornipressin). Lokaler vasokonstriktorischer Effekt und hämodynamische Auswirkungen bei Eingriffen in der Hals-Nasen-Ohren-Klinik.

POR 8 (ornipressin) at a concentration of 5 IU in 10 ml of 1% lidocaine was used as a local vasoconstrictor in 262 ENT operations. Anaesthesia was carried out with either halothane or enflurane, or with diazepam and fentanyl. The doses of POR 8 lay between 2.7 IU and 3.5 IU. Under inhalational anaesthesia there was a good vasoconstriction in 85% to 90%, and anaesthesia with diazepam-fentanyl in 60% to 83% of cases, depending on the site of operation. There should be a 10-20 minute interval between infiltration and the beginning of surgery. Under inhalational anaesthesia the systolic blood pressure fell by 10% after infiltration of POR 8, when the diastolic blood pressure rose by 6%. During diazepam-fentanyl anaesthesia the systolic blood pressure increased by 23%, the diastolic by 27%. POR 8 was not found to have an antidiuretic effect. There was no difference between the osmolality, sodium and potassium levels of 30 patients measured before infiltration and 24 hours later. Because of the minimal side effects of POR 8 on the cardiovascular system during inhalational anaesthesia we recommend the use of these substance as a local vasoconstrictor instead of epinephrine.

A comparative study of the haemostatic properties and cardiovascular effects of adrenaline and ornipressin in children using enflurane anaesthesia.

In a randomized, double-blind trial, haemostatic and cardiovascular effects of ornipressin and adrenaline were compared in 30 children requiring surgery for "bat-ear" deformity. Mean total blood loss was 14.3 ml with ornipressin and 11.7 ml with adrenaline, this difference being insignificant. There was a significant and progressive reduction in mean heart rate in children who received ornipressin, from 134 to 116 bpm (P less than 0.05), and a significant rise from 127 to 134 bpm (P less than 0.05) with adrenaline. Mean systolic pressure was unaltered by ornipressin but was significantly increased from 97 to 105 mmHg (P less than 0.05) in children receiving adrenaline. Ornipressin is as effective a haemostatic agent as adrenaline and the rises in heart rate and systolic pressure associated with adrenaline, which are factors known to predispose to the onset of ventricular dysrhythmias, do not occur with ornipressin.

Early surgical excision and grafting of burns including tangential excision.

Early excision and grafting of burns with the advent of infection control, has become a most important part of any successful therapy in burn management. By this technique, an open wound is primarily closed, and thus circumvents the possibility of infection. There is less discomfort, more rapid restoration of function, quicker discharge from hospital and earlier rehabilitation. Metabolic needs are lessened and with less scar, the cosmetic result is improved. Excision is made between the third and fifth day postburn if possible, but more delay may be necessary to determine which burns are superficial and able to spontaneously heal. No area greater than 10% of body surface area is excised and grafted at one operative session and for large burns staged excisions are necessary. A limitation of 1 1/2 hours on the operation is made so as to control shock and hypothermia and to assure a quick recovery with early re-establishment of nutrition. Ketamine is the common anaesthetic employed and viable fat is preferred as the surface on which to graft. Tangential excision is a complementary form of early excision grafting to a specific depth, and may be used alone or in conjunction with other techniques. It is of value in selected burns of the deep partial skin loss variety, especially scalds, which predominate in children. Several slices of necrotic skin are taken until a punctate bleeding surface is reached in the deep dermis and a thin to moderate thickness allograft is immediately applied. The conservation of the deep dermis limits the area to be grafted, with the likelihood of less scar formation and a resultant graft of improved texture.