Pregnancy: Atrial natriuretic peptide antagonizes the contractile effect of angiotensin II in the human uterine artery

The regulatory peptides angiotensin II (Ang II) and atrial natriureticpeptide (ANP) are believed to play important roles in the pathogenesisof pre-eclampsia. The interactions between Ang II, ANP and noradrenaline(NA) were studied in vitro on the human uterine artery. BothAng II and NA contracted the isolated vessel in a concentration-dependentway. At high doses a decrease in the contractile force inducedby Ang II but not NA was encountered. ANP inhibited the smoothmuscle activity elicited by Ang II, resulting in a dextroshiftof the concentration-response curve, and a decrease in bothE_max (the maximum contractile response) and pD2 (the negativelogarithm of the agonist concentration inducing 50% of the E_max)for Ang II. The results might indicate a specific antagonismbetween Ang II and ANP, probably at the post-receptor level.ANP did not induce any significant change in pD₂ of the concentration-responsecurve for NA. Only at the highest dose of ANP (10^–7 M)was E_max depressed. Thus, the results only indicate a weak antagonisticrelationship between NA and ANP in the human uterine artery.     

Adrenoceptors mediating contraction in the human uterine artery

Pharmacological characterization of adrenoceptors mediating smooth muscle contraction was performed in isolated preparations from the human uterine artery. The mixed alpha 1- and alpha 2-adrenergic agonist, noradrenaline (NA) and the selective alpha 1-agonists, phenylephrine and methoxamine, all contracted the smooth muscle preparations in a concentration-dependent manner. The responses were antagonized competitively by the selective alpha 1-antagonist, prazosin, yielding pA2 values for the three agonists (8.33-9.08) typical for an interaction with alpha 1-receptors. The alpha 2-selective receptor agonists, clonidine and BHT 920, did not exert any contractile effects in the isolated uterine arteries, and the alpha 2-adrenergic antagonist, yohimbine, counteracted the contractile effect of NA only at high concentrations. The concentration-response curve for NA was unaffected by the alpha 2-selective antagonists, rauwolscine and idazoxan. The results suggest that the postjunctional contractile receptors in the human uterine artery primarily are of the alpha 1 type, and give no evidence for any substantial involvement of alpha 2-receptors in this important tributary vessel of the human female reproductive tract.     

Neuropeptide Y (NPY) and sympathetic control of blood flow in oral mucosa and dental pulp in the cat

Neuropeptide Y (NPY) immunoreactivity (-IR) was found to be present in perivascular nerves in the cat dental pulp and oral mucosa. Many ganglion cells in the superior cervical ganglion also contained NPY-IR. Ligation of the inferior alveolar or lingual nerves produced an accumulation of NPY-IR in axons proximal to the site of ligation, suggesting an anterograde axonal transport of the peptide. After unilateral sympathectomy the NPY-IR disappeared in the dental pulp and oral mucosa on the ipsilateral side. Reversed phase high performance liquid chromatography showed that the main peak of NPY-like immunoreactivity found in the superior cervical ganglion co-chromatographed with synthetic porcine NPY. Changes in blood flow in dental pulp or oral mucosa were measured indirectly by recording local clearance of ¹²⁵I during electrical stimulation of the sympathetic nerve or during close intra-arterial infusion of noradrenaline or NPY. All three procedures resulted in a pronounced decrease in local blood flow of a similar magnitude in both tissues. After a-adrenoceptor blockade with phentolamine, the vasoconstrictor effect of noradrenaline was abolished. However, the effect of sympathetic stimulation after phentolamine was only partially reduced (23–54%) and the response to NPY was almost unaffected by the a-receptor blockade. The remaining effect of sympathetic stimulation after phentolamine was abolished by guanethidine. However, the response to NPY was not changed by the latter drug. In conclusion, the vasoconstrictor response in the dental pulp and oral mucosa caused by activation of sympathetic nerves is more resistant to phentolamine than the response induced by infusion of exogenous noradrenaline. Since NPY is probably co-localized with noradrenaline in the sympathetic perivascular nerves and NPY reduces local blood flow,it is proposed that this peptide is involved in sympathetic vascular control in oral tissues.     

新生儿缺血、缺氧性脑病患儿血浆INS、NPY检测的临床意义

目的:探讨了新生儿缺血、缺氧性脑病患儿血浆胰岛素(INS)、神经肽Y(NPY)水平的变化及意义.方法:应用放射免疫分析测定了94例新生儿缺血、缺氧性脑病患儿血浆INS和NPY水平及相关性研究,并与30名正常新生儿作比较.结果:新生儿缺血、缺氧性脑病患儿血浆INS和NPY水平均非常显著地高于正常新生儿组(P＜0.01),且两者呈明显正相关(r=0.6112,P＜0.01).结论:测定新生儿缺血、缺氧性脑病患儿血浆INS和NPY水平的变化与疾病的危重程度、发生发展和预后密切相关.     

Occurrence of neuropeptide Y (NPY)-like immunoreactivity in catecholamine neurons in the human medulla oblongata

We report here the coexistence of a neuropeptide and catecholamines in neurons of the human brain. Using indirect immunofluorescence histochemistry, combined with elution and restaining experiments, neurons in the medulla oblongata of man were demonstrated to contain both a neuropeptide Y-like peptide and the catecholamine synthesizing enzyme tyrosine hydroxylase.     

Changes in the expression of neuropeptide Y (NPY) during maturation of human sympathetic ganglionic neurons: correlation with tyrosine hydroxylase immunoreactivity

Developmental patterns of neuropeptide (NPY) and tyrosine hydroxylase (TH)-immunoreactivities (IR) were investigated using the method of indirect immunohistochemistry in the stellate and thoracic sympathetic ganglia of human neonates ranging in gestational age from 24 to 27 weeks (premature group) and from 38 to 41 weeks (mature group). In the paravertebral ganglia of premature neonates a small (up to 7%) population of NPY-IR nerve cells was revealed. With the gestational age increase (a mature group), a marked elevation of the number of NPY-IR ganglionic neurons (up to 41%) was noted. In contrast, in the sympathetic ganglia of premature neonates almost all the neurons were tyrosine hydroxylase immunoreactive and any change in pattern during maturation was insignificant.

The results demonstrate an age-related increase of neuropeptide Y-immunoreactivity in human paravertebral ganglia during maturation, and suggest that peptidergic co-transmission arises later in development than do the classical autonomic messengers. Adaptability of the fetus to a new external environment at birth demands a qualitatively new activity level of the autonomic nervous system, and this is provided side by side with the classical messengers noradrenaline and acetylcholine by the cotransmitter and modulating role of the neuropeptides. The appearance of neuropeptide Y in the principal sympathetic ganglionic neurons defines not only a qualitatively new level in the functional regulation of target organs at birth, but serves as an index of neonatal maturity.     

缺血缺氧性脑病患儿血清NSE和血浆NPY检测的临床意义

目的：探讨了缺血缺氧性脑病患儿血清NSE和血浆NPY水平的变化及意义。方法：应用放射免疫分析对30例缺血缺氧性脑病患儿进行了血清NSE和血浆NPY测定,并与30名正常新生儿作比较。结果：缺血缺氧性脑病患儿血清NSE和血浆NPY水平均非常显著地高于正常新生儿组（P〈0.01）,且两者呈明显的正相关（r=0.6021,P〈0.01）。结论：测定缺血缺氧性脑病患儿血清NSE和血浆NPY水平的变化与疾病的发生发展和预后密切相关。     

Interaction of noradrenaline,NPY and VIP with the neurogenic cholinergic response of the rat uterine cervix in vitro

Quantitative pharmacological studies were performed on isolated uterine cervix which was obtained from oophorectomized and oestrogen-treated rats and therefore showed no spontaneous contractility. The concentration-response curves to ACh and carbacholine were to a varying degree depressed and right-shifted in the presence of NA, but not NPY or VIP. The electrically induced cholinergic contraction was potentiated in tissues from animals pretreated with reserpine or 6-OHDA, but only at high stimulation frequencies. Histochemically, both sympatholytics abolished NA from the cervical fibres, whereas immunoreactive NPY was still encountered. Tyramine in the organ bath reduced the contraction amplitude during electrical nerve stimulation concentration-dependently by a β-adrenoceptor-sensitive mechanism. In the presence of neostigmine the amplitude was reduced by NA, but not by NPY or VIP, which, on the other hand, had an inhibitory effect in the absence of neostigmine. The results offer further support for the view that, although the cervical smooth muscle cells are equipped with adrenoceptors, the neurogenic motor response at low stimulation frequencies (around 3 Hz) is mainly cholinergic. It appears that neurally released NA is able to influence these muscle cells primarily at high frequencies. There is no clear-cut evidence that the inhibitory effects of neural NPY or VIP on the cervix of spayed, oestrogen-treated rats are mediated by postjunctional receptors.     

高血压鼠脑底动脉神经肽Y能神经与颈上神经节、星状神经节的关系

目的　探讨高血压鼠脑底动脉神经肽Y能神经与颈上神经节、星状神经节的关系。方法　应用神经节切除术和免疫组织化学ABC法 ,对 16只自发性高血压鼠脑底动脉神经肽Y能神经纤维的分布进行了观察。结果　对照组自发性高血压鼠大脑前动脉、大脑中动脉、大脑后动脉和基底动脉壁上均可见神经肽Y能阳性纤维 ,纤维似曲线状 ,多呈网状走行 ,密度较高。手术Ⅰ组作双侧颈上神经节切除术 ,脑底主要动脉的阳性纤维明显减少 ;手术Ⅱ组作双侧星状神经节切除 ,脑底主要动脉壁上的阳性纤维明显减少 ;手术Ⅲ组作双侧颈上神经节和星状神经节切除术 ,脑底主要动脉的阳性纤维完全消失。结论　自发性高血压鼠脑底主要动脉的神经肽Y能神经纤维起源于双侧颈上神经节和双侧星状神经节 ,神经肽Y能神经可能在高血压发病中起作用     

Neuropeptide Y (NPY): a vasoconstrictor in the eye,brain and other tissues in the rabbit

The effect of neuropeptide Y (NPY) on uveal vascular resistance was studied in rabbits by direct determination of uveal blood flow from a cannulated vortex vein. Regional blood flows, in the eye, the brain and several other tissues, were measured, with radioactive microspheres, during neuropeptide Y-infusion in rabbits with and without α-adrenoceptor blockade. Intravenous infusion of increasing doses of neuropeptide Y caused a dose-dependent increase in the total uveal vascular resistance. Maximal effect, a 70% increase, was achieved with 120 pmol kg^-1 min^-1. In the microsphere experiments, this dose rate was given i.v. over 10 minutes and blood flow determinations were made before and at 2 and 10 minutes after the start of the infusion. After 2 minutes of neuropeptide Y, there were marked blood flow reductions in the spleen, kidneys, adrenal glands, gastro-intestinal tract, choroid plexus and pineal and pituitary gland. The effect in the eye was small at 2 minutes, but at 10 minutes local blood flows in the choroid and the ciliary body were decreased by 50% and the iridal blood flow by 30%. Retinal blood flow was not affected by neuropeptide Y. At 10 minutes there were also significant blood flow reductions in the brain, tongue, masseter muscle and several glandular tissues. The effects of neuropeptide Y on local blood flow in rabbits that had been subjected to α-adrenoceptor blockade were very similar to the effects in the animals without α-adrenoceptor blockade. The results show that, in the rabbit, neuropeptide Y has marked effects on local blood flows in several tissues, including the eye, and suggest that neuropeptide Y may significantly contribute to the uveal vasoconstriction during sympathetic nerve stimulation.     

Neuropeptide Y inhibits Ca2+-activated K+ channels in vascular smooth muscle cells from the rat tail artery

The effects of neuropeptide Y (NPY) on the Ca²⁺-activated K⁺ channel in smooth muscle cells from the rat tail artery were studied by whole-cell and single-channel patch-clamp recording techniques. In the presence of nifedipine (1 M), whole-cell outward currents through Ca²⁺-activated K⁺ channels were inhibited by NPY in a dose-dependent manner from 20 to 200 nM. A maximum inhibition to about 48% of the control current could be achieved. Recordings from outside-out patches showed that the open probability of Ca²⁺-activated K⁺ channels were similarly inhibited by NPY. At 200 nM NPY, the open probability was reduced to about 36% of the control value. NPY did not affect the open times or current amplitude, but increased significantly the short (from 0.49 to 0.58 ms) and long (from 441 to 728 ms) closed times. Inhibition of Ca²⁺-activated K⁺ channels by NPY may contribute to its excitatory action on vascular smooth muscle cells.     

Action and localization of neuropeptide Y in the human fallopian tube

Using indirect immunohistochemistry, neuropeptide Y-like immunoreactivity was found in nerve fibers around blood vessels and in the muscle layers of the human fallopian tube. Apart from a network of immunoreactive nerve fibers in connection with the luminary epithelium of the isthmus, the distribution resembled that of adrenergic, tyroxine hydroxylase immunoreactive, nerve fibers. Neuropeptide Y was found to have a dose-dependent inhibitory action on the adrenergic contractile response to field stimulation in the external longitudinal muscle layer of the isthmus. Furthermore, neuropeptide Y inhibited [3H]noradrenaline release from isthmic preparations during field stimulation, suggesting a prejunctional inhibitory action on adrenergic neurotransmission.     

Neuropeptide Y and differential sympathetic control of splenic blood flow and capacitance function in the pig and dog

The roles of different mediators in the sympathetic regulation of the pig and dog spleens were investigated using a preparation with intact vascular perfusion in vivo. Sympathetic nerve stimulation caused overflow of neuropeptide Y-like immunoreactivity (NPY-LI) and noradrenaline (NA), arterial vasoconstriction, increase in venous blood flow and haematocrit. The dog spleen responded to single impulse stimulation, whereas more prolonged stimulation was required to elicit vascular responses in the pig spleen. Furthermore, the maximal splenic capacitance response was about 10 times larger in the dog than in the pig. After depletion of neuronal NA content by reserpine combined with preganglionic denervation, about 70% of the splenic arterial vasoconstrictor responses in the dog and pig still remained at 5 Hz stimulation. Fifty per cent of the capacitance response evoked by nerve stimulation still remained in the pig while in the dog spleen the capacitance response was virtually abolished after reserpine. The stimulation-evoked overflow of NPY-LI in pig spleen was increased several fold after reserpine treatment as compared to controls reaching levels in the venous effluent where exogenous NPY evokes vasoconstriction. In the dog spleen, overflow of NPY-LI was only observed after reserpine. Administration of NA caused arterial vasoconstriction with an initial increase in venous blood flow while NPY mainly reduced arterial blood flow. It is concluded that NA is involved in both the splenic arterial vasoconstriction and the capacitance responses while a non-adrenergic splenic vasoconstriction at least in the pig may be mediated by NPY.     

Neuropeptide Y immunohistochemistry and ultrastructure of developing chromaffin tissue in the cloudy dogfish, Scyliorhinus torazame (Chondrichthyes, Elasmobranchii)

Ontogenetic changes in neuropeptide Y-like immunoreactivity (NPY-LI) were studied in chromaffin tissue of the cloudy dogfish, Scyliorhinus torazame. In adults and post-hatching juveniles, NPY-LI was demonstrated in chromaffin cells, but not in ganglion cells and supporting cells. Immunoreactive fibers were also found in the axillary body (the major chromaffin tissue) of the adult fish. During the embryonic period, NPY-LI was found at first in chromaffin tissue in the 34-mm stage. In this stage, cells in the periphery of the tissue were positive for NPY. Afterwards, changes were not observed in the topography and relative dominance of labelled cells in the tissue. Transmission electron microscopy of chromaffin tissue of the 26-mm stage showed an early phase of histogenesis in rudimental cell clusters composed of agranular cells and a few granular cells, i.e. pheochromoblasts. In the 43-mm stage, differentiation of the chromaffin tissue enabled ultrastructural classification of adrenalin-producing cells, noradrenalin-producing cells, ganglion cells, supporting cells, and unmyelinated nerve fibers. These results suggest that in the dogfish the appearance of NPY-LI in the developing sympathoadrenal system is related to differentiation of chromaffin cells.     

Sympathetic vascular control of the pig nasal mucosa (III): co-release of noradrenaline and neuropeptide Y

The overflows of noradrenaline (NA) and neuropeptide Y like immunoreactivity (NPYLI) and vascular responses upon sympathetic nerve stimulation were analysed in the nasal mucosa of pentobarbital anaesthetized pigs. In controls, a frequency-dependent increase in NA overflow was observed whereas detectable release of NPY-LI occurred only at 6.9 Hz. Parallel decreases in blood flow in the sphenopalatine artery and vein and in nasal mucosa volume (reflecting blood volume in the venous sinusoids) were observed. The laser Doppler flowmeter signal (reflecting superficial blood flow) increased upon low and decreased upon high frequency stimulation. Twenty-four hours after reserpine pretreatment and preganglionic decentralization, the NA overflow was abolished while a frequency-dependent release of NPY-LI occurred. Forty, 60 and 80% of the vasoconstrictor responses then remained upon stimulation with a single impulse, 0.59 and 6.9 Hz, respectively. Both the vasoconstriction and NPY-LI overflow, however, were subjected to fatigue upon repeated stimulation. In reserpinized animals release of NPY-LI and vasoconstrictor responses were larger upon stimulation with irregular bursts at 0.59 Hz compared to effects seen at stimulation with continuous impulses. Pre-treatment with the a-adrenoceptor antagonist phenoxybenzamine or the monoamine reuptake inhibitor, desipramine, enhanced NA overflow by 2–3 and 1.5 times at 0.59 and 6.9 Hz, respectively. Phenoxybenzamine significantly reduced the nerve-evoked vascular responses while the release of NPY-LI at 6.9 Hz was increased. Desipramine increased the functional responses but reduced the NPY-LI overflow. During tachyphylaxis to the vasoconstrictor effects of the stable adenosine 5′-triphosphate (ATP) analogue α-β-methylene ATP (mATP) in controls, the vasoconstrictor responses as well as the NA and NPY-LI overflow to nerve stimulation were unmodified. In reserpinized animals, however, the vascular responses and the overflow of NPY-LI were reduced after mATP tachyphylaxis. These data show that both NA and NPY are released upon sympathetic nerve stimulation in the nasal mucosa in vivo and this release seems to be regulated via prejunctional a-adrenoceptors. The lack of effect of mATP tachyphylaxis under control conditions makes it less likely that ATP serves as a major mediator of the large nonadrenergic vasoconstrictor component.     

Peptide-containing nerves in the human pregnant uterine cervix: an immunohistochemical study exploring the effect of RU 486 (mifepristone).

The presence of several neuropeptides (neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), substance P (SP), galanin (GAL), enkephalin (ENK), somatostatin (SOM) was established in the early pregnant human cervix using indirect immunofluorescence immunohistochemistry. Several peptides (VIP, NPY, CGRP, GAL) were present both in free nerves among smooth muscle cells and around blood vessels. Others (SP, SOM) were only seen as single varicosities among smooth muscle cells. Randomized treatment of patients with RU 486 (mifepristone) prior to surgical sampling revealed no clearcut differences in peptide immunoreactivities. After RU 486 treatment, however, there was a tendency towards a decrease of NPY- and VIP-immunoreactivity, and an increase of CGRP-immunoreactivity.     

Prostanoid receptors in human uterine myocytes: the effect of reproductive state and stretch

In the human, prostanoids are known to be important mediators of uterine relaxation and contraction during pregnancy and parturition. We have previously shown that stretch of uterine smooth muscle cells increased prostaglandin H synthase 2 (PGHS-2) mRNA expression, PGHS-2 peptide synthesis and activity, however, the net effect on uterine contractility of this increase in prostaglandin synthesis would be determined by the expression of the different prostanoid receptors. Therefore, the aims of this study were to establish the expression of prostanoid receptor mRNA in uterine myocytes obtained from women in different reproductive states and to test the hypothesis that stretch of uterine myocytes alters prostanoid receptor mRNA expression to promote uterine contractility. Myocytes were isolated from women undergoing hysterectomy (NP) and pregnant women undergoing LSCS either before (NL) or after the onset of labour (L) and were subjected to 11% stretch for 1 h (n = 6 in all cases). Copy numbers of the individual receptors varied widely with reproductive state but followed the pattern: FP > IP = DP = EP-4 > TP = EP-3 = EP-2 > EP-1. FP mRNA expression was significantly lower in the NL group compared to the NP group and EP-3, EP-4 and TP mRNA expression was significantly lower in both NL and L groups compared to NP group levels. The level of mRNA expression of EP-1, EP-2, DP and IP did not differ between NP, NL and L groups. Stretch of cells derived from the NP group resulted in a significant decrease in EP-4 mRNA expression alone and of the NL group a significant decrease in EP-2 mRNA expression alone. Stretch had no effect on cells derived from the L group. These data show that pregnancy is associated with a significant reduction in 3 of 4 pro-contraction associated prostanoid receptor mRNA expression and 1 of 4 pro-relaxant. Stretch elicited no consistent change in prostanoid receptor mRNA expression.     

Neuropeptide Y (NPY)-like immunoreactive nerve fibers in the human and monkey (Macaca fascicularis) kidney

Nerve fibers immunoreactive for neuropeptide Y (NPY) are demonstrated for the first time by the indirect immunofluorescence technique in the human and monkey kidney. NPY-like immunoactivity (NPY-LI) is shown in a bundle of nerve fibers in the surrounding connective tissue of arteries and to a lesser extent, veins, mainly at the juxtamedullary region. Varicose nerve terminals are shown associated with blood vessels and passing between tubules in the mid and lower cortex. NPY-LI nerve fibers are also seen surrounding afferent and occasionally efferent arterioles at the vascular pole of the glomeruli. The distribution of NPY-LI nerve fibers in the monkey and human kidneys is similar to that of other species, only the quantity of the nerve fibers varies.     

Vaginal sildenafil (Viagra): a preliminary report of a novel method to improve uterine artery blood flow and endometrial development in patients undergoing IVF

Endometrial growth is thought to depend on uterine artery blood flow and the importance of endometrial development on in-vitro fertilization (IVF) outcome has been previously reported. Nitric oxide (NO) relaxes vascular smooth muscle through a cGMP-mediated pathway and NO synthase isoforms have been identified in the uterus. Sildenafil citrate (Viagra), a type 5-specific phosphodiesterase inhibitor, augments the vasodilatory effects of NO by preventing the degradation of cGMP. In this preliminary report we describe the use of vaginal sildenafil to improve uterine artery blood flow and sonographic endometrial appearance in four patients with prior failed assisted reproductive cycles due to poor endometrial response. The uterine artery pulsatility index (PI) was measured in a mock cycle after pituitary down-regulation with Lupron. The PI was decreased after 7 days of sildenafil (indicating increased blood flow) and returned to baseline following treatment with placebo. The combination of sildenafil and oestradiol valerate improved blood flow and endometrial thickness in all patients. These findings were reproduced in an ensuing gonadotrophin-stimulated cycle. Three of the four patients conceived. Although greater numbers of patients and randomized evaluation are needed to validate this treatment, vaginal sildenafil may be effective for improving uterine artery blood flow and endometrial development in IVF patients with prior poor endometrial response.