Nitric oxide regulation of corticotropin-releasing hormone release from the human perfused placenta in vitro.

We have investigated the regulatory role of nitric oxide (NO) in corticotropin-releasing hormone (CRH) release from the human perfused placental lobule in vitro. The effects of the NO donor sodium nitroprusside, the NO synthase inhibitor N omega-nitro-L-arginine, and the NO substrate L-arginine on human (h) placental CRH secretion have been studied. Single lobules of term placentae were bilaterally perfused with Krebs solution (5 mL/min; 95% O2-5% CO2; 37 C; pH 7.3). Fetal and maternal perfusates were collected at 4 C every 30 min for 3 h. CRH immunoreactivity (CRH-IR) in perfusates was measured by RIA using the 41-residue synthetic CRH as standard, 125I-labeled Tyr-hCRH as tracer, and a rabbit anti-CRH antibody Y2BO. The sensitivity of the assay was 0.13 pmol/L. Under basal conditions, human perfused placentae in vitro continuously secreted CRH-IR, which diluted in parallel to a synthetic hCRH-(1-41) standard curve. Size-exclusion chromatography of placental perfusates using a Sephadex G-50 column indicated that placental CRH-IR predominately coeluted with hCRH-(1-41) standard. Basal maternal perfusate CRH-IR levels (27 +/- 4 pmol/L) released from perfused placental lobules were nearly 10-fold greater than fetal perfusate CRH-IR levels (3.4 +/- 0.7 pmol/L; P < 0.05). Infusion of sodium nitroprusside (30-100 mumol/L) into the maternal and fetal placental circulations inhibited CRH-IR release into maternal perfusate in a concentration-dependent manner, but did not inhibit CRH-IR release into the fetal perfusate. N omega-nitro-L-arginine (100 mumol/L) increased placental CRH-IR secretion into fetal perfusate, and this effect was reversed by the infusion of L-arginine (100 mumol/L), which also reduced release below basal levels. In contrast, maternal perfusate CRH-IR levels were not affected by N omega-nitro-L-arginine or L-arginine. These results indicate that the human perfused placenta in vitro releases a substance of similar mol wt and hCRH-IR. Moreover, modulators of the NO signaling pathway differentially affect placental secretion of CRH-IR into the maternal and fetal perfusates. These data are consistent with the involvement of NO in the regulation of placental CRH release during pregnancy.

Vasodilator actions of urocortin and related peptides in the human perfused placenta in vitro.

Urocortin, is a recently isolated peptide belonging to the CRH family that binds with high affinity to the CRH2 receptor. Like CRH, urocortin causes hypotension in the rat, but its vasoactive actions have not yet been studied in the human. We have compared the vasoactive properties of urocortin, CRH, and urotensin-1 in the human fetal placental vasculature in vitro. Single placental lobules were bilaterally perfused (maternal and fetal sides, 5 mL/min each; 95% O2-5% CO2; 37 C), and changes in fetal arterial perfusion pressure were recorded. Submaximal vasoconstriction was induced by PGF2alpha (4+/-0.7 micromol/L), which increased perfusion pressure from 19.6+/-1.4 to 100.7+/-3.1 mm Hg (n=38; P < 0.001). Subsequent fetal arterial infusion of urocortin (0.001-1 nmol/L) caused concentration-dependent vasodilatation. Urocortin was equipotent with urotensin-1 and 25 times more potent than CRH in causing vasodilatation. Nevertheless, the maximum vasodilator responses to each of the peptides were similar (P > 0.05). The CRH receptor antagonist, alpha-helical CRH-(9-41) (0.2 nmol/L) significantly attenuated the vasodilatation produced by urocortin, urotensin-1, and CRH (P < 0.05). These results indicate a possible physiological role for urocortin in the modulation of human fetal placental vascular tone by activation of CRH2-like receptors.

Corticotropin-releasing hormone-induced vasodilatation in the human fetal placental circulation.

The vasoactive effects of corticotropin-releasing hormone (CRH) in the human fetal-placental circulation in vitro have been investigated. Single lobules of term placentae were bilaterally perfused with constant flows of Krebs' solution (maternal and fetal, 5 ml/min, 95% O2, 5% CO2, 37 degrees C, pH 7.3) and changes in fetal-placental arterial perfusion pressure measured. Effects of human (hCRH) and ovine (oCRH) CRH were examined during submaximal vasoconstriction (100-120 mmHg) of the fetal-placental vasculature induced by prostaglandin F2 alpha (PGF2 alpha), (0.7-2 mumol/L). During infusion of hCRH or oCRH (24-7000 pmol/L) a concentration-dependent vasodilatation was observed. Human CRH and oCRH were equipotent as vasodilator agents (regression analysis; P > 0.05; n = 5). The vasodilator response curves to human and ovine CRH were compared to prostacyclin (PGI2) (1.2-1180 nmol/L). Human and oCRH were 53 times more potent than PGI2 (regression analysis, P < 0.05; n = 5). These results indicate that CRH has powerful vasodilator properties in the human fetal-placental circulation and may play a role in control of placental vascular resistance to blood flow.

Corticotropin-releasing hormone-induced vasodilatation in the human fetal-placental circulation: involvement of the nitric oxide-cyclic guanosine 3',5'-monophosphate-mediated pathway.

This study has used an in vitro perfusion method to investigate the mechanism by which CRH causes vasodilatation in the human fetal-placental circulation. In normal term placentas, vasodilatory responses to human CRH (24-7000 pmol/L) were examined during submaximal vasoconstriction (100-120 mm Hg) of the fetal-placental vasculature induced by prostaglandin F2 alpha (0.7-2 mumol/L), KCl (50-100 mmol/L), or the thromboxane A2 mimetic, U46619 (0.05-0.5 mumol/L). Infusion of CRH caused a concentration-dependent vasodilatation that was similar in the presence of each constrictor agent (P > 0.05). The CRH antagonist, alpha-helical CRH-(9-41) (200 pmol/L), and a polyclonal CRH antiserum significantly inhibited CRH-induced vasodilatation during constriction with prostaglandin F2 alpha (P < 0.05). Vasodilatory responses to CRH were attenuated by the nitric oxide synthase inhibitor, N omega-nitro-L-arginine (100 mumol/L; P < 0.05), and the guanylate cyclase inhibitor, LY 83583 (1 mumol/L; P < 0.05), but not by the cyclooxygenase inhibitor, indomethacin (3 mumol/L; P > 0.05). In placentas of women with increased fetal vascular resistance, as demonstrated by Doppler ultrasound waveforms in vivo, CRH-induced vasodilatation was significantly reduced (P < 0.05). These results indicate that in the human fetal-placental circulation, CRH causes a vasodilatory response via a nitric oxide-/cGMP-dependent pathway. CRH may play a role in the control of vascular resistance to blood flow in the normal human placenta, and there may be a deficiency in the CRH signaling pathway of placentas with increased fetal vascular resistance.

U46619-mediated vasoconstriction of the fetal placental vasculature in vitro in normal and hypertensive pregnancies.

OBJECTIVES: To measure in-vitro responses to the thromboxane A2 (TxA2) mimetic U46619 in the fetal placental vasculature of human placentae from normotensive women and those with pre-eclampsia. Furthermore, to compare fetal vascular responses to endothelin-1,5-hydroxytryptamine, potassium chloride (KCl) and prostacyclin (PGI2) in placentae from normal or pre-eclamptic pregnancies. METHODS: Single placental lobules of intact placentae were bilaterally perfused in situ (fetal and maternal) with constant flows of Krebs' solution. Changes in fetal arterial perfusion pressure during intra-arterial infusion of vasoactive agents were recorded. Fetal placental vasoconstrictor concentration response curves were obtained to U46619 (0.01-300 nmol/l), endothelin-1 (0.4-160 nmol/l), KCl (3-300 mmol/l) and 5-hydroxytryptamine (0.03-30 mumol/l). In addition, vasodilator concentration response curves were obtained for PGI2 (1.2-350 nmol/l) in the fetal placental circulation during submaximal increases in perfusion pressure with prostaglandin F2 alpha (PGF2 alpha; 0.7-2.0 mumol/l). RESULTS: The maximum increase in perfusion pressure caused by U46619 in placentae from normotensive women was 194 +/- 25 mmHg. The maximum response to U46619 was significantly reduced in the placentae from women with pre-eclampsia (104 +/- 21 mmHg). In contrast, there were no differences in constrictor responses to endothelin-1,5-hydroxytryptamine and KCl, or in dilator responses to PGI2 in placentae obtained from either normotensive women or those with pre-eclampsia. CONCLUSION: TxA2 receptor-mediated vasoconstriction is reduced in the fetal vasculature of placentae from women with pre-eclampsia, possibly to compensate for the increased levels of TxA2 seen in these conditions.

Fetal placental vascular responses to corticotropin-releasing hormone in vitro. Effects of variation in oxygen tension.

In this study, using the human placenta perfused in vitro with Krebs' bicarbonate solution, we have examined the effects of changes in oxygen tension on the vasoreactivity of fetal placental blood vessels to corticotropin releasing hormone (CRH). Vasodilatory responses to human synthetic CRH were measured during sub-maximal vasoconstriction of the fetal placental circulation with prostaglandin F(2alpha)(PGF(2alpha)) (1-100 micrometer). Decreases in fetal placental arterial perfusion pressure (FAP) were obtained with CRH under conditions of high oxygen or low oxygen tension, >/=450 mmHg and

Effects of Bufo marinus skin toxins on human fetal extracorporeal blood vessels.

The effects of extracts of Bufo marinus toad skin toxin on human isolated umbilical arterial rings and the fetal vessels of perfused placentae were examined and compared with those of ouabain, an inhibitor of Na+/K(+)-ATPase. Umbilical artery rings and fetal vessels of the perfused placenta responded to extracts, or ouabain, with constriction which persisted after the removal of each agent. Extraction of the skin, using various solvents, revealed that the umbilical artery constriction was due mainly to the effects of water-soluble, polar compounds. Fractionation of a water extract and bioassay on the rat isolated aorta revealed maximum vasoconstrictor activity in a low mol. wt fraction. During Na+/K(+)-ATPase inactivation in the fetal circulation of the human placenta, by perfusion with K(+)-free Kreb's solution, reactivation of the enzyme by K+ infusion caused vasodilatation. This effect was inhibited both by water extracts of load skin and by ouabain. Thus, properties of some of the endogenous compounds in B. marinus skin resemble those of ouabain, by causing persistent constriction of human fetal blood vessels. A component of the vasoconstrictor response probably results from inhibition of vascular smooth muscle Na+/K(+)-ATPase, but it is likely that a contribution is also made by additional vasoconstrictor substances contained in B. marinus toxin.

Vascular responses to sodium nitroprusside in the human fetal-placental circulation.

This study examined the activity of sodium nitroprusside (SNP) in the human fetal-placental circulation in vitro in pathological and experimental conditions in which vascular function may be impaired. SNP (13-3400 nM) caused a concentration-dependent reduction in fetal arterial perfusion pressure (FAP) in Krebs' perfused placental cotyledons, at basal tone and following pre-constriction with prostaglandin F2 alpha (PGF2 alpha). SNP-induced reduction in FAP in the PGF2 alpha pre-constricted fetal-placental circulation was enhanced approximately six-fold (5.85) in those placentae pre-treated with the nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine (100 microM). Reductions in FAP in the preconstricted fetal-placental vasculature caused by SNP were not altered by prior infusion of ouabain (100 nM) into the fetal circulation or during low oxygen perfusion (O2 tension < 50 mmHg). No differences were observed in the responses obtained to SNP in placentae obtained from women with normotensive pregnancies or those associated with (i) pregnancy-induced hypertension, (ii) intra-uterine growth retardation, or (iii) an elevated umbilical-artery Doppler-ultrasound systolic/diastolic ratio, in either preconstricted placentae or those at basal tone. These findings are consistent with an up-regulation of guanylate cyclase/cGMP-mediated vasodilatation in the fetal-placental vasculature following complete blockade of endogenous NO production.

Some anti-allergic and anti-inflammatory actions of 2-N-carboxamidinonormianserin (FCC5).

The aims of these studies were to examine the effects of FCC5 (2-carboxamidino-1,2,3,4,10,14b-hexahydrodibenzo (c,f) pyrazino (1,2,-a) azepine HCl), an analogue of mianserin, on immediate type hypersensitivity reactions in-vitro. The actions of FCC5 were examined on the Schultz-Dale reaction of guinea-pig ileum and on histamine and leukotriene release from human- and guinea-pig-sensitized lung fragments. FCC5 (applied topically) was assessed for anti-inflammatory activity in-vivo against phorbol-12-myristate-13-acetate (PMA)-induced oedema in the mouse ear. FCC5 (IC50 = 0.17 microM) was a potent inhibitor of the Schultz-Dale reaction in-vitro, as assessed by a concentration-dependent attenuation of egg albumin-induced contractions of sensitized guinea-pig isolated ileum. Using human and guinea-pig isolated sensitized lung fragments, FCC5 (1-100 microM) attenuated antigen-induced release of sulphidopeptidoleukotrienes and histamine. FCC5 (50 micrograms topically) resembled mianserin and indomethacin in attenuating PMA-induced mouse ear inflammation. These properties together with previously published evidence of long lasting antihistamine properties in-vivo, suggest that FCC5 has therapeutic potential as an anti-allergic agent, especially in pathological conditions where an inflammatory component is present.

Pharmacological evaluation of the histamine H1 and 5-HT blocking properties of 2-N-(carboxamidinonormianserin) (FCC5): in-vitro studies.

Some in-vitro pharmacological effects of a novel analogue of mianserin, 2-carboxamidino-1,2,3,4,10,14b-hexahydrodibenzo (c,f) pyrazino (1,2-alpha) azepine hydrochloride (FCC5) have been studied. FCC5 was a non-competitive antagonist of both histamine-induced contractions of the guinea-pig ileum and 5-HT-induced contractions of rat fundal strips with pD'2 values of 6.13 and 5.57, respectively. The insurmountable antihistaminic effect of FCC5, 100 nM, in the guinea-pig isolated ileum was not removed by washing. FCC5, 10-100 nM, had no effect on responses to acetylcholine or barium chloride of the guinea-pig isolated ileum. In guinea-pig isolated right atria, FCC5, 1-30 microM, had no effect on H2-receptor-mediated chronotropic responses to histamine. FCC5, 10-1000 nM, had no alpha 2-adrenoceptor antagonist activity, as assessed by lack of effect on the inhibitory responses to B-HT 920 in the electrically stimulated rat isolated vas deferens. FCC5 resembles mianserin by being a potent, non-competitive antagonist at histamine H1 and 5-HT receptors, but differs from mianserin in a number of respects including having much less effect at alpha 2-adrenoceptors.

In-vivo pharmacological studies of 2-N-carboxamidinonormianserin, a histamine and 5-hydroxytryptamine antagonist lacking central effects.

The in-vivo pharmacological properties have been examined of FCC5 (2-N-carboxamidino-1,2,-3, 4, 10, 14b-hexahydrodibenzo (c.f.) pyrazino (1, 2-alpha)azepine hydrochloride), a guanidino analogue of mianserin. FCC5 (30-100 micrograms kg-1, i.v.) caused long-lasting (> 1 h) attenuation of histamine- and 5-hydroxytryptamine (5-HT)-induced bronchoconstriction in the anaesthetized guinea-pig. FCC5 (< or = 1 mg kg-1, i.v.) had no effect on submaximal bronchoconstrictor responses caused by i.v. acetylcholine or the thromboxane A2-mimetic U46619 ((15S)-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid). The pressor effects of 5-HT in anaesthetized and pithed rats were inhibited by FCC5 (0.3-1.0 mg kg-1, i.v.). Higher doses of FCC5 (3 mg kg-1, i.v.) reduced bradycardia and depressor responses to 5-HT in anaesthetized rats. In anaesthetized cats and rats and also pithed rats, FCC5 (0.1-1.0 mg kg-1, i.v.) caused sympathomimetic effects as demonstrated by pressor responses and tachycardia. FCC5 (0.1-0.3 mg kg-1, i.v.) inhibited pressor responses to tyramine whereas those to noradrenaline and sympathetic nerve stimulation were potentiated. Oedema in the rat paw caused by intraplantar 5-HT was inhibited by FCC5 (ID50 0.76 mg kg-1, i.p.; and 2.7 mg kg-1, p.o.). In decerebrate rats which had been spinalized at T6-8, fenfluramine-induced facilitation of the flexor reflex of the anterior tibialis muscle was inhibited by mianserin (ID50 0.36 mg kg-1, i.p.) but not by FCC5 (< or = 3 mg kg-1, i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

The action of 1,2,3,5,6,11b-hexahydro-[1]benzothieno [3,2-g]indolizine hydrochloride (ADT 16) on peripheral and central responses mediated by 5-hydroxytryptaminergic and adrenergic systems of the rat.

Some acute pharmacological effects have been examined of racemic ADT 16 (1,2,3,5,6,11b-hexahydro[1]benzothieno[3,2-g]indolizine hydrochloride), on peripheral and central responses mediated by 5-HT and adrenergic systems in the rat. In-vitro, ADT 16 (10-1000 nM), similarly to mianserin, antagonized the inhibitory responses to B-HT 920 of the electrically-stimulated rat isolated prostatic vas deferens. High concentrations of ADT 16 (10 microM), also resembled those of mianserin by potentiating twitch responses to electrical stimulation of the tissue. Contractile responses to phenylephrine of rat isolated epididymal vas deferens were antagonized by ADT 16 (0.3-1 microM). In the rat stomach fundus strip, ADT 16 (1-3 microM) antagonized contractions due to 5-HT. ADT 16 (0.1-1 microM) had no effect on responses to acetylcholine of the guinea-pig isolated ileum. In-vivo, in spinalized, decerebrated rats, fenfluramine- or clonidine-induced facilitation of flexor reflex activity of the anterior tibialis muscle was attenuated by ADT 16 (3 and 10 mg kg-1, i.v., and 3 mg kg-1, i.v. respectively). In the anaesthetized rat, L-3,4-dihydroxyphenylalanine (L-dopa)- or L-5-hydroxytryptophan (L-5-HTP)-induced increases in the frequency of spontaneous twitches of the anterior digastricus muscle were attenuated by ADT 16 (1 and 3 mg kg-1, i.v.; n = 4). It is concluded that ADT 16, similarly to mianserin, is a novel peripherally and centrally active antagonist of 5-HT and adrenergic responses in the rat.

Intracoronary photodynamic therapy reduces neointimal growth without suppressing re-endothelialisation in a porcine model.

OBJECTIVE: To examine the effects of intracoronary PhotoPoint photodynamic therapy (PDT) with a new photosensitiser, MV0611, in the overstretch balloon and stent porcine models of restenosis. METHODS: 28 pigs were injected with 3 mg/kg of MV0611 systemically 4 h before the procedure. Animals were divided into either the balloon overstretch injury (BI) group (n = 19) or the stented group (n = 9). After BI, a centred delivery catheter was positioned in the artery to cover the injured area, and light (532 nm, 125 J/cm(2)) was applied to activate the drug (n = 10). Control arteries (n = 9) were not activated by light. In the stented group, the drug was light activated before stent deployment. Serial sections of vessels were processed 14 days after treatment in the BI group and 30 days after treatment in the stented group for histomorphometric or immunohistochemical analysis. RESULTS: Intracoronary PDT significantly reduced intimal thickness in both BI and stented arteries (about 65%: 0.22 (SEM 0.05) mm v 0.62 (0.05) mm, p < 0.01; and about 26%: 0.40 (0.04) mm v 0.54 (0.04) mm, p < 0.01, respectively). PDT increased luminal area by

Pharmacological evaluation of two novel analogues of mianserin: 2-N-carboxamidinonormianserin (FCC5) and 2-N-carboxamidonormianserin (FCC13).

1. The pharmacological properties have been examined of FCC5 (2-N-carboxamidinonormianserin) and FCC13 (2-N-carboxamidonormianserin), two novel analogues of mianserin. 2. FCC5 or FCC13 (100 micrograms/kg, i.v.) caused long-lasting (greater than 1 h) abolition of 5-hydroxytryptamine (5-HT) and histamine-induced bronchoconstriction in the anaesthetized guinea-pig. Both analogues had no effect (up to 1 mg/kg, i.v.) on bronchoconstriction caused by acetylcholine (25-50 micrograms/kg, i.v.). 3. The pressor effects of 5-HT in pithed rats were significantly attenuated by FCC5 (0.1 mg/kg, i.v.) or FCC13 (0.5 mg/kg, i.v.). 4. Oedema in the rat hind paw caused by intraplantar 5-HT was inhibited by FCC5 (ID50 0.76 mg/kg, i.p.; 2.7 mg/kg, p.o.) or FCC13 (ID50 0.65 mg/kg, i.p.; 5.8 mg/kg, p.o.). 5. In the central nervous system (CNS), FCC13 caused antagonism of 5-HT activity. It inhibited: (i) L-5-hydroxytryptophan (L-5-HTP)-induced head twitches in mice (ID50 1.85 mg/kg, i.p.), (ii) fenfluramine-induced facilitation of flexor reflex activity (FRA) in spinalized decerebrate rats (SDR) (IC50 0.57 mg/kg, i.p.). 6. FCC5 (less than or equal to 30 mg/kg, i.p. and less than or equal to 3 mg/kg, i.p., respectively) had no effect in either test. In contrast to mianserin, it also had no overt central actions as (less than or equal to 30 mg/kg, i.p.) had no effect on: (i) morphine-induced catalepsy (MIC) or (ii) clonidine-induced facilitation of FRA in SDR. However, high doses of FCC13 inhibited MIC (ID50 20 mg/kg, i.p.), but had no effect on (ii) (less than or equal to 10 mg/kg, i.p.). 7. Thus, FCC5 and FCC13 are potent, orally active H1 and 5-HT receptor antagonists. However, in contrast to FCC13 and mianserin, FCC5 did not cause CNS-mediated effects.

Multple criterion screen for identifying secondary school children with psychiatric disorder: characteristics and efficiency of screen.

A multiple criterion screen was developed as part of a study which was designed to assess different types of intervention for school children with psychiatric disorder. The foremost requirement was that false positives be kept to a minimum, with selected children being unequivocally disturbed. Children were identified for treatment by the following measures: (a) teacher rating on the Rutter B2 Scale, giving a total score and subscores for neurotic and antisocial behaviour; (b) peer ratings on a sociometric measure, yielding isolation and rejection scores; and (c) self ratings on the Junior Eysenck Personality Inventory, specifically the neuroticism dimension. A weighting system was developed so that children could be selected on the basis of extreme scores on either teacher or self-rating measures alone, or by a combination of less extreme scores on more than one measure. The results are presented and discussed.

Actions of magnesium, nifedipine and clonidine on the fetal vasculature of the human placenta.

The anticonvulsant magnesium and the antihypertensives clonidine and nifedipine are extensively used for the clinical treatment of preeclampsia and eclampsia. Little, however, is known about the possible effects of these agents on human fetal-placental vascular resistance. We therefore examined the actions of these agents on the human fetal placental vascular bed in vitro relating the concentrations causing any vasoactive effects to the maternal blood levels attained during treatment. Placentas (n = 24) were obtained within 20 minutes of delivery from women (aged 30.2 +/- 0.9 years). In each a placental lobule was bilaterally perfused with Krebs' solution (5 mL/minute, 37 degrees C, 95% O2, 5% CO2) and fetal arterial inflow pressure (FAP) monitored. Submaximal vasoconstriction of the fetal vascular bed was induced by continuous infusion of prostaglandin F2 alpha (4.2 +/- 0.5 microM) which increased FAP from 25.9 +/- 3.9 to 95.1 +/- 6.2 mm Hg. Using a group of placentas for each drug, the effects of MgCl2, nifedipine and clonidine, were examined. Magnesium (0.3-100 mM) (n = 4) dilated the placental fetal circulation with an IC50 of 8.1 mM and a maximal response of 89.7 +/- 3.6% (n = 4). This effect of Mg2+ was not changed during concomitant infusion of the cyclo-oxygenase inhibitor, indomethacin (3 microM). Nifedipine (3-10,000 nM) also produced vasodilatation (maximum response 42 +/- 9%, n = 5). Clonidine (3-1,000 nM) caused no significant change (p < 0.05 n = 5) in vascular resistance (maximum response 11.2-5.7%) relaxation), when compared to controls. Thus in concentrations likely to be therapeutically present in maternal blood, magnesium causes a greater degree of placental fetal vasodilatation than does nifedipine, whereas clonidine is unlikely to have any effect on fetal placental vascular resistance.

Effect of inhibition of nitric oxide synthase and guanylate cyclase on hydralazine-induced vasodilatation of the human fetal placental circulation.

1. The vasodilator effects of hydralazine in vitro, using the Krebs' perfused human placental lobule was studied. Single placental lobules were bilaterally perfused (maternal and fetal sides 5 mL/min each, 95% O2, 5% CO2, 37 degrees C) and changes in fetal arterial pressure (FAP) and venous outflow (VO) were recorded. 2. Submaximal vasoconstriction was induced by KCl (20-50 mmol/L), which increased basal FAP from 22.8 +/- 1.7 to 91.3 +/- 3.9 mmHg (n = 9, P < 0.001), and decreased VO from 4.1 +/- 0.6 to 0.2 +/- 0.1 mL/min (n = 6, P < 0.01). 3. Hydralazine caused vasodilatation (IC50 1.9 mmol/L, n = 9) and increased VO in the presence of KCl-induced vasoconstriction. 4. Infusion of N omega-nitro-L-arginine (100 mumol/L) to block nitric oxide synthase caused the basal FAP to increase from 30.9 +/- 5.9 to 47.4 +/- 6.7 (n = 6, P < 0.05) and significantly potentiated hydralazine-induced vasodilatation (n = 7, P < 0.05). 5. The soluble guanylate cyclase inhibitor LY 83583 (6-anilino-5,8-quinolinedione) (1 mumol/L) significantly antagonized the vasodilatation produced by hydralazine (n = 5, P < 0.05). 6. Thus, Hydralazine appears to activate guanylate cyclase, leading to increased cyclic GMP in fetal arterial vascular smooth muscle to cause vasorelaxation. No evidence was obtained to suggest that hydralazine exerted its action by either releasing nitric oxide from endothelial cells in the placenta or acting as a nitric oxide donor.

Autacoids and control of human placental blood flow.

1. Humans have a haemochorial, villous placenta. Uterine blood passes through maternal sinuses, bathing placental villi through which fetal blood circulates. Blood flow through each circulation is high and vascular resistance low. This haemodynamic situation is essential for efficient placental function. 2. The low placental vascular resistance is due to a lack of nervous influences together with pregnancy-induced changes promoting vasodilatation. Increases occur in output of the vasodilators prostacyclin and nitric oxide and also in membrane sodium pump activity. 3. Many autacoids are present in umbilical blood. Fetal vessels of the placenta develop intense vasoconstriction in the presence of some autacoids, such as thromboxane A2 and prostaglandins F2 alpha and E2, and respond weakly to others, such as angiotensin II and 5-hydroxytryptamine. Nevertheless, vasodilator influences predominate. 4. The diseases of pre-eclampsia and fetal growth retardation are associated with reduced output of nitric oxide and prostacyclin and with increased production of thromboxane A2 and endothelin-1. These changes promote vasoconstriction, increased vascular sensitivity to vasoconstrictor stimuli, platelet aggregation and intravascular coagulation, retarding blood flow and feto-placental growth. 5. Aspirin and glyceryl trinitrate have been investigated for possible therapeutic use in pre-eclampsia and fetal growth retardation. Improved drug therapy is likely as knowledge increases of the importance of autacoids in normal placental function and in the changes that occur during disease.

A clinical trial of phenelzine in anxiety depressive and phobic neuroses.

A double-blind clinical trial of phenelzine and diazepam against placebo and diazepam in neurotic patients over a four-week period showed phenelzine to be superior to placebo on three rating scales in some groups of patients who completed the trial. The findings suggest that phenelzine may exert a beneficial effect on some as yet undefined features of anxiety and depression which were not revealed by a multiple regression analysis of clinical symptomatology or premorbid personality.