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At least 19 recordsLinked to original sources
PubMed1992

Emergency symphysiotomy for the trapped head in breech delivery: indications, limitations and method.

Careful case selection can avoid most obstetrical emergencies. However, even with optimum management of breech labour, the fetal head may become trapped. Since doctors in developing nations must be prepared for this dire situation, this article reviews breech case selection and outlines the steps in breech delivery, illustrating symphysiotomy for the entrapped head. The limitations and precautions associated with symphysiotomy are stressed.

Breech Presentation↗
PubMed1976

Transplacental passage of diazepam following intravenous injection immediately prior to operative vaginal delivery.

The early phase of diaplacental transfer of diazepam was studied in 39 women given the drug as a basic anaesthetic for operative vaginal delivery indicated by prolonged second stage of labour (9 cases), breech delivery (19 cases) and intrauterine hypoxia (11 cases). A total dose of 30 mg diazepam (Valium Roche) was injected intravenously over a period of 15 sec umbilical cord blood was collected immediately after delivery. Diazepam was extracted with diethyl ether and determined by gas chromatography. The concentration of diazepam in cord blood increased from greater than 5-250 ng/ml at 57-60 seconds to 48-1861 ng/ml at 90-100 seconds after completion of the intravenous injection. Thereafter a plateau seemed to be reached but the interindividual variation was still great with values ranging from 45-3034 ng/ml up to 360 seconds. Judged by Apgar score and the clinical course the neonates seemed to be unaffected by the medication administered to the mother.

Anesthesia, Obstetrical↗
PubMed1989

Detection of human papillomavirus deoxyribonucleic acid by filter in situ hybridization during pregnancy.

Samples taken from 101 healthy pregnant women (49 over and 52 under the 20-week gestational period) and 108 healthy nonpregnant women were tested for human papillomavirus (HPV) types. Using 6, 11, 16, and 18 HPV DNA probes, 3-5 x 10(5) exfoliated cells scraped from the cervix were tested by filter in situ hybridization (FISH). Thirty-five of the pregnant women (34.6%) had evidence of the presence of HPV DNA: with 11.8% (12/101) HPV 6; 7.9% (8/101) HPV 11; 8.9% (9/101) HPV 16; and 5.9% (6/101) HPV 18 positivity. HPV DNA was detected in 20.4% (22/108) of the non-pregnant women. Compared with the healthy, nonpregnant group, the higher level of asymptomatic cervical HPV infection was mainly due to the accumulation of HPV 16 and 18 nucleic acids during the gestational period: with detection of HPV 16 in 8/49 cases (16.3%) and of HPV 18 DNA sequences in 4/49 (7.6%) cases. Screening 6-8 weeks after delivery indicated a decline of HPV positivity. Of the 4/12 HPV type 16 positive mothers, only one retained the presence of HPV 16 DNA, whereas neither of the 2/12 type 18 positive women reacted after birth with the type 18 radioactive probe.

DNA Probes, HPV↗
PubMed1979

Natural history of placenta previa ascertained by diagnostic ultrasound.

Placental localization by diagnostic ultrasound was performed at 16 to 18 weeks' gestation in 1,098 patients prior to amniocentesis for genetic indications. Placenta previa was diagnosed in 58 patients, 47 of whom went on to delivery uncomplicated by placenta previa. There were five patients with placenta previa at delivery, four of whom had third-trimester bleeding. One patient was diagnosed as having a normal placental implantation at midtrimester but placenta previa was demonstrated at delivery. The incidence of placenta previa at 16 to 18 weeks' was 5.3% and fell to 0.58% at delivery, indicating a 90% conversion rate. Thus the vast majority of cases of asymptomatic placenta previa remain so and convert before delivery. These patients should be observed with serial ultrasound at 6 to 8 week intervals until delivery or unequivocal conversion. No restriction in activity seems indicated unless the placenta previa persists beyond 30 weeks or becomes clinically manifest.

Adult↗
PubMed1992

Neonatal periventricular-intraventricular hemorrhage after maternal beta-sympathomimetic tocolysis. The March of Dimes Multicenter Study Group.

OBJECTIVE: Our objective was to determine if the rate of periventricular-intraventricular hemorrhage is increased in the offspring of women who received a beta-sympathomimetic agent as part of the management of preterm labor. STUDY DESIGN: This retrospective study consists of 2827 women who were delivered of a singleton, live infant free of congenital neurologic anomalies between 25 and 36 completed weeks of gestation during a multicenter preterm birth prevention trial. The data were analyzed, adjusting for type of tocolytic agent, race, infant sex, gestational age, birth weight, health care center, route of delivery, indication for delivery, intrapartum fetal distress, respiratory distress syndrome, and neonatal sepsis. RESULTS: The overall incidence of periventricular-intraventricular hemorrhage in this population was 5.6%. In a univariate analysis in which no adjustment was made for potentially confounding variables, beta-sympathomimetic tocolysis was found to be associated with nearly a fourfold increase in the incidence of periventricular-intraventricular hemorrhage when compared with the use of either magnesium sulfate or no tocolytic agent. The results of a multivariate regression analysis revealed that beta-sympathomimetic agents were associated with a statistically significant increase in the overall incidence of periventricular-intraventricular hemorrhage (odds ratio 2.47, 95% confidence interval 1.34 to 4.56, p = 0.004) and a similar, but not significant, increase in the incidence of grades 3 and 4 periventricular-intraventricular hemorrhage (odds ratio 2.50, 95% confidence interval 0.96 to 6.48, p = 0.06). CONCLUSION: beta-Sympathomimetic tocolytic therapy may be associated with a more than twofold increase in the incidence of neonatal periventricular-intraventricular hemorrhage.

Birth Weight↗
PubMed1992

Midtrimester pregnancy termination: a randomized trial of prostaglandin E2 versus concentrated oxytocin.

OBJECTIVES: The purpose of this study was to determine whether a concentrated oxytocin infusion can reliably effect uterine evacuation in the midtrimester and whether such an infusion is associated with fewer side effects than prostaglandin E2 vaginal suppositories. STUDY DESIGN: Patients received either prostaglandin E2 (n = 42) or oxytocin (n = 45) for indicated midtrimester abortions in a prospective, randomized trial. Treatment consisted of either prostaglandin E2 vaginal suppositories (one every 4 hours) or infusions of an escalating concentration of oxytocin (one every 4 hours). Unless delivery had occurred or was imminent after 24 hours, the agent was considered to have failed, and patients were crossed to the alternative method. RESULTS: Delivery indications were similar between the two groups. There were 6 (14%) first-agent failures with prostaglandin E2 and 9 (20%) with oxytocin (p = 0.48). Considering the failures and subsequent crossovers, 103 patient trial regimens were completed. Fever, nausea, vomiting, and diarrhea were more frequent with prostaglandin E2 (p < 0.005). CONCLUSIONS: Concentrated oxytocin is a satisfactory alternative to prostaglandin E2 for midtrimester abortion.

Abortifacient Agents↗
PubMed1988

[Comparison of Doppler flow measurements of the arcuate artery and uterine artery in fetal growth retardation].

Transabdominal Doppler velocimetry in the arcuate arteries has been the widest used technique for the assessment of uterine perfusion despite theoretical and physiological drawbacks. The size of arcuate arteries is beyond the resolution of modern scanners. They represent terminal branches of the uterine vasculature and do not provide information regarding total uterine blood supply. Transvaginal Doppler velocimetry of the main uterine arteries on its course through the parametrium by means of a newly developed frontally radiating 240-degree "panorama" sector scanner promised a solution. The aim of the study was to compare the A/B ratios in both arteries (i.e. arcuate vs. main uterine) in pregnancies with a growth retarded fetus below the 10th percentile, as defined by ultrasound biometry. We wondered firstly which vessel better demonstrates velocity waveforms leading to growth retarded newborns defined by a birth weight beyond the 10th percentile (Hohenauer) and secondly, how frequently pathological A/B ratios in the uterine vessels are associated with pathological A/B ratios in the umbilical arteries. In 25 growth retarded fetuses (ultrasound biometry), we found more often pathological waveforms in the arcuate arteries (n = 20) than in the main uterine arteries (n = 18). Pathological waveforms in all three vessels (arcuate, main uterine, umbilical) were found in 12, in the arcuate and umbilical vessels in 13, and in the main uterine and in umbilical artery in 17 cases. Six fetuses were within the normal weight range at delivery indicating normal fetal growth. Pathological A/B ratios in the main uterine artery were more often associated with a growth retarded newborn.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Failure of chloroquine prophylaxis for falciparum malaria in pregnant women in Madang, Papua New Guinea.

Six hundred and twenty pregnant women, living under conditions of year-round transmission of malaria in a rural coastal area of Madang, Papua New Guinea (PNG), were followed while attending mobile antenatal clinics and receiving chloroquine prophylaxis (300 mg base weekly). Whole blood chloroquine concentrations measured by ELISA from samples collected at delivery indicated a high level of drug compliance in regular attenders. Susceptibility is increased in primigravidae to Plasmodium falciparum but not to other malaria species, with the peak prevalence occurring at nine to 16 weeks gestation. The incidence of P. falciparum infection per person-month was 20% for primigravidae, 25% for those gravida 2, 17% for those gravida 3 or greater, and 14% for non-pregnant nulliparae. Some 8.7% of primigravidae and 9.5% of those gravida 2 had persistent infections. Prophylactic chloroquine is required in this pregnant population because of altered host immunity during pregnancy, but is reduced in efficacy because of chloroquine resistance. Despite this, a missed clinic attendance resulted in a two-fold increase in incidence for all pregnant women, indicating that chloroquine was having some effect.

Animals↗
PubMed1992

N omega-amino-L-arginine, an inhibitor of nitric oxide synthase, raises vascular resistance but increases mortality rates in awake canines challenged with endotoxin.

Inhibitors of nitric oxide synthase (NOS) have been reported to increase mean arterial pressure in animal models of sepsis and recently have been given to patients in septic shock. However, controlled studies to determine the effects of these agents on cardiovascular function and survival in awake animal models of sepsis have not been reported. To examine the therapeutic potential of NOS inhibition in septic shock, we challenged canines with endotoxin (2 or 4 mg/kg i.v.) and treated them with either normal saline or N omega-amino-L-arginine (10 or 1 mg/kg/h), the most specific inhibitor available for the isoform of NOS implicated in septic shock. Endotoxemic animals treated with N omega-amino-L-arginine (n = 11) had higher systemic and pulmonary vascular resistance indices (SVRI and PVRI, p less than or equal to 0.033) and decreased heart rates (p = 0.009), cardiac indices (CI, p = 0.01), oxygen delivery indices (p = 0.027), and oxygen consumption indices (p = 0.046) compared with controls (n = 6). Moreover, N omega-amino-L-arginine increased mortality rates after endotoxin challenge (10 of 11 vs. 1 of 6 controls, p = 0.005). Administration of L-arginine did not improve survival or alter the cardiopulmonary effects of N omega-amino-L-arginine, which suggests that inhibition of NOS may not have been competitive. In normal animals, N omega-amino-L-arginine alone (n = 3) increased SVRI (p = 0.0008) and mean arterial pressure (p = 0.016), and decreased CI (p = 0.01) compared with saline-treated controls (n = 3), but, at the high dose, also produced neuromuscular rigidity and seizure-like activity that was not apparent in the endotoxemic model. Thus, the mortality rate from endotoxemia increased either because of NOS inhibition per se or because of properties unique to N omega-amino-L-arginine, or both.

Amino Acid Oxidoreductases↗
PubMed1979

A study of the plasma concentrations of lorazepam in mother and neonate.

A standard dose of lorazepam 2.5 mg was given i.v. to two groups of mothers: (a) before surgical induction of labour and (b) at the beginning of the second stage of labour. A group of non-pregnant women was studied as control. Plasma concentrations of lorazepam were measured by gas-liquid chromatography, in the mothers before delivery, and in the mother and neonate at delivery and 24 and 48 h thereafter. Concentrations at delivery in the neonates were similar to those in the mothers in group (a), but significantly less in group (b). Fetal concentration rarely exceeded that in the mother. Measurements after delivery indicated that the neonates were able to metabolize lorazepam at the same rate as the mothers. Of the 22 neonates studied only one had an Apgar score of less than 8 at 5 min and this score was 10 at 10 min.

Adult↗
PubMed1992

Hemodynamic and metabolic effects of epinephrine during cardiopulmonary resuscitation in a pig model.

BACKGROUND AND METHODS: This study was designed to assess the effect of epinephrine during cardiopulmonary resuscitation (CPR) on left ventricular myocardial blood flow, systemic oxygen delivery and consumption, and on plasma glucose and lactate concentrations. Fourteen pigs were allocated to receive either 0.9% saline (n = 7), or 45 micrograms/kg epinephrine (n = 7) after 5 mins of ventricular fibrillation, and 3 mins of open-chest CPR. Left ventricular myocardial blood flow was measured with radiolabeled microspheres. Plasma catecholamine concentrations were measured by high-pressure liquid chromatography. RESULTS: During open-chest CPR, mean (+/- SD) values of left ventricular myocardial blood flow before, 90 secs, and 5 mins following drug administration were 49 +/- 10, 46 +/- 12, 43 +/- 15 mL/min/100 g, respectively, in the control group, and 52 +/- 12, 118 +/- 21, 84 +/- 28 mL/min/100 g, respectively, in the epinephrine group (p less than .05 at 90 secs and 5 mins). At the same time points, mean (+/- SD) oxygen delivery indices were 7.7 +/- 3.0, 6.0 +/- 2.1, 6.5 +/- 2.7 mL/min/kg in the control group and 7.6 +/- 2.5, 5.3 +/- 2.1, 5.5 +/- 1.9 mL/min/kg in the epinephrine group (nonsignificant). Mean oxygen consumption indices were 5.8 +/- 2.4, 4.6 +/- 1.6, 5.2 +/- 2.6 mL/min/kg in the control group and 5.4 +/- 1.6, 4.2 +/- 1.6, 4.4 +/- 1.4 mL/min/kg in the epinephrine group (nonsignificant). During CPR and before epinephrine administration, arterial plasma epinephrine concentrations increased from prearrest values of 0.77 +/- 0.70 to 62.1 +/- 48.7 micrograms/L, and plasma norepinephrine concentrations increased from 0.28 +/- 0.32 to 104.3 +/- 57.1 micrograms/L. After administered epinephrine, there was an additional increase to 271 +/- 83 micrograms/L at 90 secs in arterial plasma epinephrine, but no important alteration in the plasma norepinephrine concentration. At no time point could we find a clinically important difference in plasma glucose or lactate concentrations between the two groups. CONCLUSIONS: At a dose of 45 micrograms/kg, epinephrine caused an increase in left ventricular myocardial blood flow after a total of 8 mins of cardiac arrest, including 3 mins of CPR, while not altering systemic oxygen delivery and consumption, plasma glucose, or lactate concentrations.

Animals↗
PubMed1989

Group B streptococcus and premature rupture of membranes and preterm delivery.

In a population of 1,050 pregnant women the effect of maternal colonization by group B Streptococcus on premature rupture of membranes (PROM), preterm delivery, and low weight was analyzed. A significant increment was found of the prevalence of PROM for patients colonized in the vagina and/or the rectum (26.4%) versus noncarrier patients (17.8%). In vaginal and/or rectal group B Streptococcus carriers, in whom group B Streptococcus was also isolated from the cervical culture, the rate of PROM was higher (41.7%), while when the cervical culture was negative, the PROM was similar to noncarriers. THere were no significant differences with respect to colonization conditions regarding the incidence of preterm delivery or the different preterm delivery indicators analyzed.

Carrier State↗
PubMed1991

Ventilatory drive and respiratory muscle function in pregnancy.

It has been demonstrated that during pregnancy expiratory reserve volume (ERV) decreases and minute ventilation (VE) increases initially and then stabilizes. In order to determine the role of thoracoabdominal mechanics, control of breathing, and inspiratory muscle function in these alterations, we studied inspiratory pressures, lung volumes, thoracic configuration, and respiratory drive in 18 normal pregnant women at Weeks 13, 21, 30, and 37 of pregnancy. Ten of them were studied 6 months after delivery. Transdiaphragmatic pressure (Pdi) was measured at Week 37 and 3 months after delivery in an additional group of seven women. VE as well as VT/TI increased early during gestation and remained unchanged thereafter. In contrast, mouth occlusion pressure (P0.1) increased progressively during pregnancy, from 1.53 +/- 0.16 (mean +/- SE) to 2.02 +/- 0.18 cm H2O, and fell significantly to 1.1 +/- 0.15 cm H2O after delivery, indicating that effective respiratory impedance increases during pregnancy. Mean P0.1 correlated with progesterone plasma levels (r = 0.918 p less than 0.05). No changes in Plmax, PEmax, and Pdimax, were observed. End-expiratory gastric pressure (Pga) increases significantly during pregnancy: 11.8 +/- 0.8 versus 8.4 +/- 1.12 cm H2O after delivery (p less than 0.012). This increment was correlated with the fall in ERV observed in late pregnancy (r = 0.74 p less than 0.05). Our results demonstrate that during pregnancy ventilatory drive and respiratory impedance increase with the consequent stabilization of VE, but our data do not permit us to differentiate whether the increment in P0.1 is secondary to the increase in impedance or to the rise in progesterone. Respiratory muscle function remains normal despite the alteration of thoracic configuration.

Adult↗
PubMed1989

Angiotensin II stimulates early proximal bicarbonate absorption in the rat by decreasing cyclic adenosine monophosphate.

These studies explored the hypothesis that angiotensin II increases bicarbonate absorption in the proximal convoluted tubule (PCT) by decreasing intracellular cAMP. In vivo microperfusion was performed in rat PCT with measurements of bicarbonate absorption and of tubular fluid cAMP delivery, as a reflection of intracellular cAMP. Intravenous angiotensin II potently increased S1 PCT bicarbonate absorption (348 +/- 11 to 588 +/- 8 peq/min.min, P less than 0.001) and decreased tubular fluid cAMP (18 +/- 2 to 12 +/- 2 fmol/mm.min, P less than 0.05). Parathyroid hormone had the expected opposite effects, which were additive to those of angiotensin II. Over a wide range of hormonal activities, there was an excellent inverse relationship between hormonally modulated bicarbonate absorption and cAMP delivery. Pertussis toxin pretreatment significantly attenuated (by 35-45%) the angiotensin-induced increase in bicarbonate absorption and decrease in cAMP delivery, indicating Gi-protein intermediation. Luminal dibutyryl cAMP abolished the transport response to angiotensin II. In conclusion, these in vivo results suggest angiotensin II stimulates bicarbonate absorption in the S1 PCT by a G1-mediated depression in intracellular cAMP.

Adenylyl Cyclases↗
PubMed1987

Long term effects of a first pregnancy on the hormonal environment: estrogens and androgens.

An early (but not a late) first pregnancy is known to be protective for breast cancer. This effect might be mediated through a long term change in the hormonal environment caused by the early first pregnancy. To investigate the possibility of such a change we carried out a prospective longitudinal study of serum and urinary estrogens and serum androgens in four groups of women, namely early (age, 18-23 yr) first pregnancy (n = 15), early control (n = 20), late (age, 29-40 yr) first pregnancy (n = 9), and late control (n = 20). The pregnancy groups were studied before (initial visit) and 7-19 months after a first pregnancy (return visit). The control groups were similarly studied, but without an intervening pregnancy. The following were measured: serum estrone (E1), 17 beta-estradiol (E2), estriol (E3), and E1 sulfate; urinary total E1, E2, E3, and glucosiduronates of these three estrogens; and serum testosterone, dehydroepiandrosterone sulfate (DHAS), and dehydroepiandrosterone (DHA). There was no significant change between the initial and return visits in serum E1, E2, E1 sulfate, or any of the urinary estrogens in either pregnancy group or in the corresponding control groups. There was, however, a significant increase in serum E3 between initial and return visits for both pregnancy groups compared with the control values. There was no significant change in serum testosterone. There was a marked significant decrease in both serum DHAS and DHA between initial and return visits in both pregnancy groups compared with the corresponding control group values. There was also a significant increase in the serum E3 to DHA ratio in both pregnancy groups. A cross-sectional study (measuring serum DHAS and DHA only) was then carried out in a series of parous and nulliparous women. The serum DHAS and DHA levels were markedly and significantly lower in parous than in nulliparous women, as expected. There was no significant relationship between serum DHAS or DHA levels and months elapsed (up to 150) since last delivery, indicating that the changes last at least for this period of time. There was no significant relationship between serum DHAS or DHA levels and parity (one to three previous pregnancies), indicating that the changes occur only after a first pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Human corticotropin-releasing hormone during pregnancy.

Elevated irCRH levels up to 14 ng/ml were measured in 176 females in the last trimester. The highest maternal CRH levels were found in those females in whom the period from the onset of labour to full dilatation of the cervix and the time span of delivery were shortest. irCRH in amniotic fluid (120 +/- 180 pg/ml; n = 14) was in the same range as in umbilical cord plasma (233 +/- 188 pg/ml; n = 66) and 20-fold lower than in prepartal maternal plasma (5.38 +/- 4.49 ng/ml; n = 66). irCRH in maternal plasma correlated highly to irCRH in umbilical cord plasma (p less than 0.001; n = 66). After delivery irCRH disappeared from maternal plasma with a half-life of 50 minutes (n = 14). One day postpartum irCRH levels (n = 22) were undetectable. The height of the irCRH levels in the various biological fluids did not correlate to the mode or the pathological events of delivery (n = 43). Maternal ACTH levels above the normal range were encountered only in women immediately prepartal and did not correlate to the CRH levels (253 +/- 229 pg/ml; n = 66). Cortisol levels were higher in maternal plasma than in umbilical cord plasma due to elevated CBG (n = 78). Free cortisol levels were higher in the 3rd trimester than in the 1st (2.18 +/- 0.16 vs 1.16 +/- 0.73 ng/ml; n = 42). irCRH in maternal and umbilical cord plasma correlated to the hPl and estriol levels (p less than 0.001 and p less than 0.05; n = 66). We conclude that irCRH is secreted by the placenta into both maternal and fetal circulation. Though placental CRH is undistinguishable from hypothalamic CRH, the biological significance of placental CRH remains open. Our data show that placental CRH might be responsible for the changed function of the adrenal gland during pregnancy, with higher free cortisol levels in the last trimester. The extremely elevated ACTH levels during labour and delivery indicate that CRH is not the only mediator of stress-induced ACTH secretion in the regulation of the maternal hypothalamo-pituitary-adrenal axis.

Adolescent↗
PubMed1991

Dopamine distribution and behavioral alterations resulting from dopamine infusion into the brain of the lesioned rat.

In an effort to verify the "dopamine secretion hypothesis" as the mechanism responsible for the antiparkinsonian efficacy of adrenal medullary transplants into the brain, the effects of dopamine infusion into the brains of rats with unilateral substantia nigra lesions were examined. The apomorphine-induced rotation, characteristic of this animal model, was diminished after 7 days of continuous dopamine infusion (10 micrograms/hr) into the ipsilateral striatum, whereas intraventricular infusion was without effect. Chromatographic analysis of the dopamine distribution after 10 days of infusion into either region revealed that ipsilateral delivery of dopamine did not result in contralateral increases in dopamine content. Examination of the adjacent striatum following ipsilateral intraventricular delivery indicated that dopamine had only penetrated 1 mm. Even with intrastriatal delivery, there were still parts of the infused striatum which had below-normal levels of dopamine. The fact that striatal tissue presents a significant barrier to the penetration of dopamine is discussed in relation to adrenal medullary and fetal nigral transplants.

Adrenal Medulla↗
PubMed1976

Respiratory rhythmicity in the cat.

Brain stem respiratory neuron activity in the cat was studied in relation to efferent outflow (phrenic discharge) under the influence of several forcing inputs: 1) CO2 tension: hypocapnia produces disappearance of firing in some neurons, and conversion of respiratory-modulated to continuous (tonic) firing in others. 2) Lung inflation: during the Bruer-Hering reflex, some neurons have "classical" responses and others have "paradoxical" responses (i.e., opposite in direction to peripheral discharge). 3) Electrical stimulation: stimulus trains to the pneumotaxic center region (rostral lateral pons) produce phase-switching, whose threshold is: a) sharp (indicating action of positive-feedback mechanisms), and b) dependent on timing of stimulus delivery (indicating continuous excitability changes during each respiratory phase). Auto- and crosscorrelation analysis revealed the existence of short-term interactions between: a) medullary inspiratory (I) neurons and phrenic motoneurons; b) pairs of medullary I neurons; c) medullary I neurons and expiratory (E) neurons. A model of the respiratory oscillator is presented, in which the processes of conversion of tonic to phasic activity and switching of the respiratory phases are explained by recurrent excitatory and inhibitory loops.

Action Potentials↗