How the U.S. press covers the Canadian health care system

The U.S. media dwell on what they perceive as the shortcomings of the Canadian health care system, and minimize the advantages of providing free medical care for all. Focusing on specialization and high-tech treatments as the most important measure of health care quality, the media overlook the importance of greater access to medical care in promoting health. At the same time, the U.S. media are reluctant to cite the higher infant mortality rates and lower life expectancy rates in the United States compared with Canada.

Developmental steps for radionuclide hysterosalpingography

The active oviductal transportation capacity was studied in 73 infertile women by the use of a new deposition technique of radioactive particles into the internal cervical os. The main reason for this study was that a previous observation had shown that such a transportation capacity was lacking in 41% of the infertile patients with a normal hysterosalpingogram. The examination was performed in the immediate preovulatory phase, i.e. on days -3 to 0 before the ovulation, as measured by the basal body temperature during two preceding cycles. The deposition of 99mTc-labelled albumin particles of 0.2-1.0 micron at the internal cervical os and the interpretation of the radionuclide images are described in detail. The results show that the bilateral active tubal transportation capacity was present in 42 patients. An impaired transportation capacity was diagnosed in 22 patients. In 9 patients, the particles never reached the uterine cavity, or all activity leaked back to the vagina.

Forces required for dilatation of human cervix in first trimester of pregnancy

Cervical resistance to dilatation was measured in 76 patients undergoing first trimester legal abortion; a specially designed force-sensing instrument was used. No correlation between cervical resistance and patient age or gestational age was found. Increasing parity and earlier legal abortions were significantly correlated with a lowering of the cervical resistance. In patients dilated to 11 mm a lowering of resistance was noted suggesting a tear in cervical tissue.

Cervical dilatation before first trimester elective abortion: a comparison between laminaria and a newly developed hydrogel tent, the A rod

The effect of cervical dilatation prior to first trimester abortion by laminaria tent and a newly developed hydrogel tent, the A rod, was studied on 50 patients undergoing first trimester legal abortion. The effect was measured both clinically and by the use of an objective measure of cervical resistance. No significant difference in cervical dilatation was found after 5 h of treatment.

Evaluation of the clinical method of measuring cervical dilatation after treatment of the cervix prior to first trimester abortion

A comparison of the subjectively measured cervical dilatation and the dilatation measured objectively with a force-sensing instrument connected to metal dilators was made in two studies of cervical treatment prior to first trimester abortion. It was concluded that the subjective method is a sensitive and accurate method of measuring cervical dilatation but does not allow for comparison between different studies where an objective method of measurement should be used.

Transcervical sterilization in the human female by hysteroscopic application of hydrogelic occlusive devices into the intramural parts of the fallopian tubes: 10 years experience of the P-block

The development of the hydrogelic occlusive device called the P-block is described including developmental steps of the design of the device as well as the experience gained concerning the hydrogel of the device, shelf life, animal and human toxicology, insertion techniques, analgesia, check-up for retention in situ, actual efficacy of the method, mode of action of the device, complication rates, patient acceptance, continuation rates, possible reversibility and future perspectives of the method. Over a period of 10 years more than 900 woman years were observed. The gross Pearl Index for the total series of nine different designs of P-blocks is 5, due to rejection of the device on either or both sides. The corresponding value for intact P-blocks in situ is 0.3. With the latest version of P-blocks--Mark 9--a total of 191 women have been observed over 637 woman years during a mean of 21 months with a maximum time of observation of 88 months in the single case. The continuation rate, when no pregnancy occurs is 99% over 10 years. After unilateral expulsion and intra-uterine pregnancy 48% return for reinsertion of P-blocks. The rate of complications, including extra-uterine pregnancies was neglectable as was the loss for follow-up. Life table analysis revealed that no pregnancy occurred after 30 months from the insertion of P-blocks.

Cardiac gas embolism during carbon dioxide hysteroscopy: risk and management

A relatively high number of fatal complications during hysteroscopy, where carbon dioxide was used as the uterine distension medium, plus a recent report on heart embolism during dog experiments with venous carbon dioxide infusion, audible by simple stethoscopic surveillance during the infusion, prompted the present study. Seventy women with no history of cardiac valvular disease or failure were observed during carbon dioxide hysteroscopy for the occurrence of the characteristic metallic heart sound caused by the intracardiac presence of free carbon dioxide during the heart contractions. In seven cases (10%) the typical metallic heart sounds appeared during the hysteroscopy, leading to immediate interruption of the hysteroscopy and withdrawal of the hysteroscope. This caused the pathological heart sounds to disappear, after which the hysteroscopy could continue. Heart auscultation should always be performed during carbon dioxide hysteroscopy in order to avoid serious cardiovascular complications. This simple precaution turns carbon dioxide hysteroscopy into a versatile and safe method for intra-uterine diagnosis and therapy.

Sonographic localization of an intramurally placed intratubal device--the P-block

Hysteroscopical application of hydrogelic non-medicated occlusive devices, P-blocks, in the intramural part of the human fallopian tube has become an alternative to abdominal sterilization. The check-up procedure involved repeated hysteroscopies at certain intervals. These check-ups had to be confined to the early proliferative phase of the menstrual cycle in order to get maximum vision. In view of this and as the number of patients increased, practical and administrative problems arose. The need for other methods to check the P-blocks in situ after the first insertion and later became very urgent. Linear-array ultrasound and hysterosalpingography were tried, both methods failing to reveal the exact intramural position of the P-blocks. Finally, transabdominal scanning by use of modern sonographic equipment (phase array electronic sector system) made it possible to detect the exact position of the P-blocks. Furthermore, transvaginal examination appeared to have a very high sensitivity as well as specificity even in cases with sharply retroflected uteri. Our achievements in the field of sonographic examination of intratubal devices are presented.

Second look laparoscopy; evaluation of two different antibiotic regimens after treatment of acute salpingitis

In order to have their diagnoses verified, etiology determined and treatment evaluated, 64 patients with suspected acute salpingitis (AS) underwent laparoscopy during which specimens were taken. The patients were referred to groups of either a mild (16/64), a moderate (26/64), or a severe (22/64) form of salpingitis. They were then randomized to one of two groups for treatment with either doxycycline/bensylpenicillin-procain (DC/BP) or trimethoprim-sulfamethoxazole (TMP-SMZ). The results were evaluated by second-look laparoscopy 3-6 months later when adhesions and tubal passage were looked for. Isolates from the cervix were culture positive for Chlamydia trachomatis (CT) in 36/64 (56%) (9/16 with a mild form, 13/26 with moderate form and 14/22 with a severe form of salpingitis). Neisseria gonorrhoeae (NG) was isolated from the cervix in 15/64 (23%) (5/16 with a mild form, 4/26 with a moderate form and 6/22 with a severe form of the disease). Oviductal cultures for CT were found in 12/64 (19%) (1/16 with a mild form, 4/26 with a moderate and 7/25 with severe form of salpingitis). Oviductal isolates for NG were found in 2/64 (13%) (2/16 from the group with a mild form of the disease). Second-look laparoscopy revealed totally occluded oviducts in two patients from the group with a severe form of salpingitis (one from each treatment group).

Measurement of human cervical compliance

A critical evaluation of the various methods for the measurement of the compliance of the human cervix uteri was made. The resistance of this tissue to a dilating force was measured by a previously constructed strain gauge instrument equipped with exchangeable Pratt cervical dilators. The dilating resistance offered by the cervical canal was recorded on a polygraph at a constant paper speed. Control experiments in which the dilating instrument was allowed to meet artificial cellulose tissue showed that the peak value recorded was of importance for estimating cellulose tissue resistance. Measurements of the area under the curve were shown to be of minor importance in this system. Using this technique in clinical applications, it was also shown that peak resistance provides the most accurate measurement of human cervical resistance.

Radionuclide hysterosalpingography for measurement of human oviductal function

A clinical method is described and claimed to evaluate the active transportation capacity of the luminal epithelium lining the human uterus and fallopian tube. After intracervical application of technetium-labelled human albumin spheres at 1-2 days before ovulation this radioactivity could be followed by gamma-camera when moved in ad ovarian direction. This method is called radionuclide hysterosalpingography (RN-HSG). The results were compared to the findings at normal hysterosalpingography (HSG). By use of this method it was possible to verify active passage in cases of tubal spasm at HSG, lack of transport in cases of normal patent oviducts at HSG as well as presence or absence of active transport through sactosalpinges with or without fimbrial passages to the abdominal cavity as seen at normal HSG. Congruent findings between HSG and RN-HSG was observed in 49%. The studied oviducts were found to be patent with normal HSG but lacked transportation capacity when studied by RN-HSG in 41%. The clinical use of this method is discussed in view of the selection of patients for different forms of in vitro fertilization and egg transfer (IVF-ET).

Serum levels of estrogens and of five 'steroid sensitive' proteins in early normal pregnancy

Serum concentrations of sex hormone binding globulin (SHBG), pregnancy associated alpha 2-glycoprotein (alpha 2-PAG), caeruloplasmin (Cp), alpha 1-antitrypsin (alpha 1-At) and transferrin (Tf), unconjugated and total estrone, and unconjugated estradiol-17 beta were measured twice at a 4-5 week interval in 43 cases of early normal pregnancy (gestational weeks 6-19). Significant correlations between estrogen and protein levels in the total material were observed for all proteins except for Tf. However, within 2-week intervals of pregnancy, significant correlations were obtained only in certain intervals between estrogens on one hand and SHBG, Cp and alpha 1-At on the other. Significant correlations between rates of increase of estrogens and of proteins were obtained only at certain occasions for SHBG, Cp, Tf and alpha 1-At. The results indicate that, although estrogens may have a modulatory function in 'steroid-sensitive' protein synthesis, they are probably not the main physiological regulator.

Observations on the mode of action of an intratubal device, the P-block

A hydrogelic intratubal device, called P-block, Mark 9, was inserted hysteroscopically with local anesthesia in the intramural part of the fallopian tube of 25 women referred for the procedure as an alternative to abdominal sterilization. Hysterosalpingography revealing bilateral oviductal patency was followed by hysteroscopic checkup verifying bilateral presence of P-blocks, except in three patients who had expulsion of the P-blocks on one side. All of the 22 patients had retention of the P-blocks 6 to 7 months after insertion. None became pregnant. Thus it is suggested that an intratubal device in the isthmic part of the human fallopian tube acts as an intrauterine contraceptive device, preventing intratubal and intrauterine pregnancies. Endeavors to explain the contraceptive effect of a nonocclusive intratubal device are discussed on the basis of our present knowledge of tubal physiology. Distension of part of the human isthmus is likely to disturb normal gamete transport through the isthmus.

Salpingitis; aspects of diagnosis and etiology: a 4-year study from a Swedish capital hospital

359 patients underwent laparoscopy to verify the diagnosis of salpingitis. Pelvic inflammatory disease (PID) was found in 187 (52%) cases. Laparoscopy revealed normal conditions in 136 (37%) cases. Other diseases were diagnosed in 36 (10%) cases. Bacteriological cultures from the fimbrial lumen were positive in 24% of the PID cases. Chlamydia trachomatis (CT) was detected in 12%, Bacteroides species (BS) in 5%, Actinomyces israelii (AI) in 3%, Gardnerella vaginalis (GV) in 2%, Neisseria gonorrhoeae (NG) in 1%, and Ureaplasma urealyticum (UU) in 1%. Cervical cultures were positive for NG and/or CT in 71% of the PID cases but only in 19% of the non-PID cases. From these no positive intra-abdominal cultures were detected. Serological tests for CT were carried out. A positive acute titre of greater than or equal to 1/64 was noted in 37%, a seroconversion (X4) 2-3 weeks later was found in 14%. Positive serology despite a negative culture was registered in 19%.

Oestrogen and thyroxine-binding globulin levels in early normal pregnancy

Peripheral serum levels of thyroxine-binding globulin (TBG), unconjugated and total oestrone, and unconjugated oestradiol-17 beta were measured twice in 60 cases of early normal pregnancy (gestational weeks 6-19). Although highly significant correlations between TBG and oestrogen levels were obtained in the total material, the correlations within two-week intervals of pregnancy were rather poor and mostly insignificant. Furthermore, there were no associations at all between the increase rates of TBG and those of the oestrogens, either within two-week intervals or in the total material. The findings do not support the common concept of continuously rising oestrogen stimulation as the main factor affecting the TBG synthesis during pregnancy.

Adenosine modulation of adrenergic neurotransmission in the human fallopian tube

The effects of adenosine and adenosine analogues on nerve-induced contractile responses and [3H]noradrenaline ([3H]NA) release, were studied in the isthmic part of human oviducts. Adenosine and L-N6-phenylisopropyladenosine (L-PIA) could enhance neurogenic contractile responses in preparations obtained mainly in the proliferative phase. At higher concentrations, adenosine derivatives inhibited contractile responses to nerve stimulation in both proliferative and secretory phase, with the potency order: 5'-N-ethylcarboxamideadenosine (NECA) greater than or equal to L-PIA much greater than D-PIA. This indicated actions at both stimulatory A1- and inhibitory A2-receptors. Adenosine, L-PIA and NECA but not D-PIA inhibited [3H]NA release during nerve stimulation. The relative potency order for the prejunctional inhibition was compatible with an action at A1-receptors. Furthermore, adenosine was found to modulate nerve-induced contractions via postjunctional stimulatory A1- and inhibitory A2-like receptors. The postjunctional effects may be influenced by cyclic hormonal changes. The adenosine antagonist 8-p-sulfophenyltheophylline (PSøT) reversibly antagonized the stimulatory and inhibitory effects by adenosine and analogues.

Thyroxine-binding globulin in spontaneous abortion

Thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), thyroxine (T4), free T4, triiodothyronine (T3) and thyroid-stimulating hormone (TSH) were studied in 144 apparently healthy, euthyroid pregnant women displaying miscarriages. In an additional group of 18 aborting women a frozen blood sample drawn in early pregnancy was similarly analyzed for the thyroid components as well as for human chorionic gonadotropin (HCG). The values were compared to those of normal pregnancies (n = 228) at corresponding intervals. Significantly lower values of TBG were found in the spontaneously aborting group. A significantly lower value of TBG was found to be more predictive concerning spontaneous abortion than that of HCG.

Therapeutic ureteral occlusion in advanced pelvic malignant tumors

A technique for ureteral occlusion, combining insertion of nylon plugs with injection of polidocanol, is described. The method was used in 15 patients with vesicovaginal fistulas after operation and irradiation for advanced gynecological malignancy, or with severe malfunction and fibrosis of the bladder after radiotherapy for bladder carcinoma. The urinary leakage ceased in 11 patients, was greatly diminished in 2 and was unchanged in 2. Migration of plugs to the renal pelvis was the most serious complication and may have been the cause of pyelonephritis in 1 case. The technique is recommended for patients with a short life expectancy and uncontrolled, distressing leakage of urine.

Long-term toxicity of a hydrogelic occlusive device in the isthmus of the human oviduct. A light microscopic study

Ten women applying for sterilization volunteered for a tubal blocking procedure. An occlusive device of gamma polymerized hydrogel, a P-block, was applied in the isthmic part of the oviduct by trans-cervical hysteroscopy. Bilateral expulsion occurred in three and unilateral in six subjects. Six patients became pregnant. The P-block was in position from one week to 32 months. Histologically, the reaction to the P-block was first erosion and acute unspecific inflammation. Later there was a histiocytic and foreign-body reaction due to dissolution of the hydrogel. When the P-block was expelled no changes were present in the material.

Doxycycline in human oviduct mucosa and plasma 24-30 hours after an oral dose of 100 mg

Oviductal and peripheral plasma concentrations 24 hours after the last dose of Doxycycline (DC) were studied in 17 patients. The concentration of DC in healthy oviduct mucosa was 1.3 micrograms/g (range 0.6-1.7) and 1.1 micrograms/ml (range 0.6-1.7) in plasma. One patient with severe chronic salpingitis in acute exacerbation showed 3.6 micrograms/g in tissue and 2.4 micrograms/ml in plasma in proliferative phase.

The A-rod--a new possibility for cervical dilation and/or induction of uterine contractions for abortion or delivery by combined pharmacological and mechanical action

A hydrogel compound (Sauflex, Special Polymers Ltd., London) which has the capacity to swell by absorbing surrounding fluid, was found to be capable of absorbing prostaglandins (PGE1, PGF2 alpha) in alcohol or saline during this process. After evaporation of the hydratized hydrogelic compound which restored its initial proportions and stiffness, rehydratization of the hydrogelic compound caused it to release the respective prostaglandin to the surrounding medium or tissues. The endocervical canal of first-trimester abortions was dilated by plain mechanical action of a rod-shaped hydrogel body (A-rod) inserted in the cervical canal. By loading the A-rod with PGF2 alpha (2-110 mg) the cervical canal was additionally widened and abortive contractions were elicited in the uterus. Further implications of the medical use of the A-rod are discussed.

Levels of ampicillin and doxycycline in human oviduct mucosa and serum

A common treatment for salpingitis today includes ampicillin (AMPI) and doxycycline (DC), the former against Neisseria gonorrhoeae and the latter against Chlamydia trachomatis. The concentrations of doxycycline in oviduct mucosa were found about equal to that of serum and well above the minimum inhibitory concentrations (MIC's) for the bacteriae in question. The concentration of AMPI in the oviduct mucosa was only about 1/40 of that in serum, i.e. 1/10 of the MIC, which jeopardizes the effectivity of AMPI in the treatment of salpingitis.

Thyroid associated components in serum during normal pregnancy

Thyroxine-binding globulin (TBG(, thyroxine-binding pre-albumin (TBPA), thyroxine (T4), free-T4, triiodothyronine (T3), and thyroid-stimulating hormone (TSH) were studied throughout apparently normal pregnancy in 290 cases grouped in 2 week intervals. TBG increased to a plateau level reached in the 24th week and was hereafter unchanged until term. T4 showed an increase until the 16th week of pregnancy and levelled off to a constant level for the rest of the pregnancy. Free-T4 declined to almost subnormal values for the non-pregnancy state which was reached around the 20th week of pregnancy. T3 showed a slight and definite increase in the beginning of pregnancy and levelled off to a constant value after the 14th week. TSH increased towards the end of pregnancy also showing its maximum during the last 4 weeks. TBPA showed constant values throughout pregnancy. The results are discussed in view of the use of modern techniques and previously missing data in literature (TBPA).

Sex-dependent induction of human suppressor T cells by chorionic gonadotropin

Human chorionic gonadotropin (hCG) in physiological retroplacental concentration has been shown to induce human female lymphocytes which suppress the proliferation and differentiation of B cells stimulated by purified protein derivative of tuberculin. To test whether the hCG-induced suppression was sex dependent parallel experiments using female and male peripheral lymphocytes were performed. hCG did not induce cells capable of suppressing purified protein derivative induced B cell proliferation in lymphocytes from males, which was in contrast to lymphocytes from females where a statistically significant suppression was found. A similar hCG-induced suppressive effect was found before menarche, after the menopause and in two patients with Turner's syndrome, suggesting that a gene(s) on the Y chromosome exerts a regulatory function and thus prevents the hormone from inducing suppressor T cells.

Levels of trimethoprim and sulfamethoxazole in human oviduct mucosa and plasma

The oviductal and plasma levels of trimethoprim (TMP) and sulfamethoxazole (SMZ) were studied in 9 women after oral and i.v. administration of a drug combination (Eusaprim R, Wellcome Foundation Ltd). The concentration of TMP in a healthy endosalpinx was found to be twice as high (4.7 microgram/g, range 2.8-8.3) as in plasma (2.6 microgram/ml, range 2.1-3.6). Conversely, the endosalpingeal level of SMZ (38 microgram/g, range 12-65) was about half that in plasma (77 microgram/ml, range 58-95). The agar well diffusion method was used for the concentration determinations. The specimens were collected during surgery for non-infectious genital diseases. The implication of treatment by the given drugs is discussed.

In vitro induction of human suppressor T cells by a chorionic gonadotropin preparation

Human chorionic gonadotropin (hCG) in physiological retroplacental concentration has been shown to possess the capacity of inducing human lymphocytes which are subsequently competent to depress an antibody response induced by purified protein derivative of tuberculin, phytohemagglutinin, lipopolysaccharide and pokeweed mitogen. These suppressor cells inhibited the T cell-dependent mitogen-induced activation of lymphocytes synthesizing IgM, IgG and IgA. No suppression by hCG-induced cells was observed in Epstein-Barr virus activated cell cultures, indicating a T cell origin of the target cell. It is suggested that this may represent a mechanism for the cellular basis of an hCG-induced immunosuppressive effect in pregnancy.

In vitro induction of murine suppressor T-cells by human chorionic gonadotropin

Human chorionic gonadotropin (HCG) has previously been considered to be immunosuppressive and, thus, by prohibiting maternal rejection of the fetal transplant, to be one of the factors responsible for the successful outcome of pregnancy. The mechanism by which HCG exerts its pregnancy retaining effect is, however, as yet unknown. The present study shows that HCG has the capacity in mice of inducing lymphocytes which are subsequently competent to depress a polyclonal antibody response induced by different B cell mitogens. It is therefore suggested that HCG may exert its feto-protective action by inducing suppressor T cells. These lymphocytes would thus prevent the activation of cells which are responsible for transplant rejection.

Frequency-dependence of 3H-noradrenaline secretion from human vasoconstrictor nerves: modification by factors interfering with alpha-or beta-adrenoceptor or prostaglandin E2 mediated control

Isolated superfused field stimulated human omental arteries and veins, preincubated with 3H (-)-noradrenaline (NA) were used to study the frequency dependence of NA secretion and of the mechanisms for its local feedback control. 3H-NA secretion per shock was found to be basically a simple hyperbolic function of the stimulation frequency from 1 to 30 Hz, as long as secretion was restricted by prostaglandin E2 (PGE2). In the absence of restriction, or during facilitation, 3H-NA secretion per shock reached its maximum at 10 Hz and then declined at 30 Hz, indicating 'overload' in some link in the secretory mechanism. 3H-NA secretion was depressed by exogenous NA and by PGE2, and enchanced by isoprenaline, phentolamine and by blockade of PGE2 formation. Most of these effects were inversely related to the stimulation frequency. Attempts were made to study interactions between the different control mechanisms and to evaluate possible in vivo consequences of disturbance of adrenergic neuroeffector transmission by interference with the local control of the secretory mechanisms.

Changes of bone mineral content during pregnancy and lactation

In order to study changes in the calcium depots of the body during pregnancy and lactation, bone mineral deteminations were performed on fourteen pregnant women and eighteen mothers post partum by X-ray spectrophotomeyry. Pregnant women exhibited a loss in trabecular bone but not in cortical bone when measured once during late first or early second trimester and again one week post partum. Lactating women who nursed less than three months lost mineral during the first three months and than regained it while those who nursed for longer than three months had no losses during six months of study.

The effect of miconazole on vulvo-vaginal candidosis in pregnant and non-pregnant women and their partners

Miconazole cream (Daktar vaginal cream 2%, Leo) given for 12-14 days was tested in 85 subjects with positive vaginal candida culture. Eighty percent of the patients were pregnant. Healing was observed in 93% of the cases. Treatment of the sexual partner did not influence the therapeutic effect.

Ultrastructure of the nerves in veins from human omentum

To study the ultrastructural characteristics of the sympathetic nerve terminals of human omental veins, and of their relationship to the innervated smooth muscle cells, biopsy specimens were taken during abdominal surgery, rapidly fixed in glutaraldehyde/osmium and stained with uranylacetate. The results indicate that the veins have an extensive noradrenergic innervation, penetrating into the tunica media. The distance between nerve terminals partly or wholly free from enveloping Schwann cells, to the surface of smooth muscle cells ranged from 30 to 500 nm. Large dense core vesicles were prominent in both preterminals and terminal regions, while small dense core vesicles occurred mainly in terminals. Large dense core vesicles in close contact with the axolemma were occasionally observed, indicating involvement in secretion by exocytosis.

Beta2-adrenoceptors facilitating noradrenaline secretion from human vasoconstrictor nerves

Isolated biopsy specimens of human peripheral arteries and veins, preincubated with 3H-(-)- noradrenaline (NA) to label the neural stores of NA, were used to study the Beta-adrenoceptors previously found to increase the secretion of 3H-NA evoked by electrical field stimulation of the adrenergic nerves of this tissue. The increase in nerve stimulation induced secretion of 3H-NA caused by 0.04 muM isoprenaline was prevented by 1 muM propranolol. This beta-blocking drug by itself slightly but significantly depressed the secretion of 3H-NA caused by nerve stimulation in the absence of isoprenaline. While the secretion of 3H-NA was not affected by known beta1-agonists, it was dose-dependently and reversibly increased by two different beta2-agonists. The effect of isoprenaline on 3H-NA secretion was not altered by a selective beta1-antagonist, but strongly reduced or abolished by a beta2-blocking drug. The results indicate that the beta-adrenoceptors involved in the control of NA secretion from the vasoconstrictor nerves of human omental blood vessels are only to a minimal extent stimulated by NA secreted from the nerves, and therefore do probably not mainly serve to mediate local positive feedback control of transmitter secretion; the receptors appear to be beta2 in nature.

Affinity of Noradrenaline and dopamine for neural alpha-receptors mediating negative feedback control of noradrenaline secretion in human vasoconstrictor nerves

Isolated superfused field stimulated biopsy specimens of human peripheral arteries and veins, preincubated with 3H-( - )-NOradrenaline (NA) to label the neural stores of NA, were used to study the potency of dopamine (DA) and of NA as triggers of alpha-adrenoceptor mediated negative feedback control of sympathetic neurotransmitter secretion, evoked by stimulation with trains of 300 shocks at 1 Hz. In this preparation DA was found to be only slightly less potent than NA in depressing both the secretion of 3h-na, and the contractile response, evoked by nerve stimulation. DA depressed the contraction evoked by exogenous NA as well, but to a very much smaller extent. On the other hand, DA was a very weak agonist on the alpha receptors of the smooth muscle; nearly 1000 times higher concentrations of DA were required to mimick contractions evoked by exogenous NA. The results show that the neural alpha-receptor function involved in control of NA secretion differs considerably from the alpha-receptors of e.g. smooth muscle, with respect to sensitivity to DA. It seems possible that the observed depressing effect of DA on NA secretion may be of pharmacological and clinical interest; it may at least in part explain the vasodilating effect of DA infusions in man.