STUDIES ON THE LOCALIZATION OF CIRCULATING ANTIGEN-ANTIBODY COMPLEXES AND OTHER MACROMOLECULES IN VESSELS. II. PATHOGENETIC AND PHARMACODYNAMIC STUDIES

Localization of circulating antigen-antibody complexes in vessels of guinea pigs by means of anaphylactic shock was found to be mediated by histamine that was released at the time of anaphylaxis. The source of the histamine may have been the mast cell as noted in studies employing a direct attack on the mast cells by octylamine. Platelets played apparently little to no role in guinea pigs in the anaphylactic deposition of circulating complexes. Rat anaphylatoxin was found to cause vascular localization and symptoms of anaphylaxis identical with that brought about by antigen-antibody anaphylaxis. This also was found to be dependent upon the release of histamine. Antibody against Forssman antigen in the vessel walls of the guinea pigs also led to deposition of circulating complexes. This was found not to be histamine dependent. The possible role of local increase in vascular permeability in certain experimental disease states in the localization of circulating complexes is discussed.

THE INFLAMMATORY RESPONSE TO IMPLANTATION OF COTTON PELLETS IN THE RAT

The subcutaneous implantation of a cotton pellet in the rat evokes a short-lasting phase of increased capillary permeability lasting some 20 min. after implantation followed by a more sustained phase which occurs after 2·5–3 hr. The early increase is antagonised by lysergic acid diethylamide, reserpine and 5-HT. The peak granuloma weight is reached at 2 days, and then falls rapidly. Antagonism of oedema and granulation tissue by hydrocortisone and reserpine can be demonstrated at 2 days after implantation.

A SENSITIVE METHOD FOR THE ASSAY OF ANGIOTENSIN

A method is described for the assay of angiotensin on the rat colon. Under the conditions of the assay, the preparation is sensitive to angiotensin and relatively insensitive to 5-hydroxytryptamine, to histamine and to other substances which might be present in blood. Bradykinin and catechol amines do not interfere with the assay. Evidence is given for the specificity of the angiotensin receptors.

BEHAVIORAL-NEUROCHEMICAL CORRELATION IN REACTIVE AND NONREACTIVE STRAINS OF RATS

Male and female rats of the Maudsley reactive and Maudsley nonreactive strains were tested in the open-field to obtain ambulation and defecation scores. They were later killed, and their brains were dissected into five portions and analyzed for serotonin. Males defecated more and ambulated less than females, and nonreactive males ambulated more and defecated less than reactive males. These behavioral differences were significant (p .05). A statistically significant difference was found for the amounts of serotonin in specific regions of the brain between males and females (males higher) and between reactive and nonreactive males (reactive higher). Significant negative correlations between serotonin values in specific regions of brain and ambulation scores were found in these animals viewed as a group or even within a given strain and sex.

THE 5-HYDROXYTRYPTAMINE CONTENT OF THE PLACENTA AND FOETUS DURING PREGNANCY IN MICE

5-Hydroxytryptamine (5HT) levels were measured in blood and tissues from pregnant mice. Blood levels remained constant during pregnancy and were the same as those in nonpregnant female mice. Placental levels of 5HT increased throughout pregnancy as did the foetal levels. The maternal blood volume of the placenta also increased with advancing gestation. 5HT levels were measured after treatment of the mother with 5HT, and the critical placental level of 5HT observed at about the time of death of the foetus was determined. The levels of 5HT in the placenta and foetus after treatment of the mother with several monoamine oxidase inhibitors were measured, and found to show no significant increase above the normal levels in these tissues. Treatment with cyproheptadine, a 5HT antagonist, did not delay parturition.

EFFECTS OF BACTERIAL ENDOTOXIN ON RABBIT PLATELETS. 3. COMPARISON OF PLATELET INJURY INDUCED BY THROMBIN AND BY ENDOTOXIN

The platelet injury produced by bacterial endotoxin and thrombin have been compared in studies utilizing citrated rabbit platelet-rich plasma. Endotoxin-induced platelet injury is characterized by a lag period, is progressive, and does not produce gross clot formation. Thrombin-induced platelet injury is immediate, non-progressive, and is associated with clot formation. The quantity of thrombin required to produce clot formation in this citrated system is less than that required to produce release of platelet 5-hydroxytryptamine. The endotoxin-induced platelet injury required extremely large quantities of heparin for inhibition. The platelet injury induced by thrombin can be inhibited by small quantities of heparin. It is concluded that the injurious effects of endotoxin on platelets is mediated through some mechanism other than thrombin formation.

ACTION OF DEXAMPHETAMINE ON 5-HYDROXYTRYPTAMINE RECEPTORS

Dexamphetamine contracted isolated preparations of rat stomach, dog retractor penis, rabbit aorta, rabbit uterus and all sections of guinea-pig ileum. Adrenaline inhibited rat stomach and all but the terminal 10 cm of guinea-pig ileum, but contracted dog retractor penis, rabbit aorta, rabbit uterus and the terminal portion of the guinea-pig ileum. 5-Hydroxytryptamine contracted all five preparations. Responses to dexamphetamine and 5-hydroxytryptamine were not blocked in preparations protected by a high concentration of either drug during exposure to phenoxybenzamine in a dose which usually caused block. Responses to dexamphetamine and 5-hydroxytryptamine were blocked in preparations protected by adrenaline. Responses to dexamphetamine in dog retractor penis, rabbit aorta and rabbit uterus were not reduced in preparations from animals treated with reserpine or after cocaine, indicating that the contraction is not mediated by released noradrenaline. It is concluded that dexamphetamine acts directly on 5-hydroxytryptamine receptors in these smooth muscles and therefore cannot be regarded as a true sympathomimetic amine.

THE SUBCELLULAR LOCALIZATION OF DOPAMINE AND ACETYLCHOLINE IN THE DOG CAUDATE NUCLEUS

The distribution of dopamine (3,4-dihydroxyphenylethylamine) between the subcellular fractions from homogenates of dog caudate nucleus was compared with the distributions of acetylcholine, 5-hydroxytryptamine and lactate dehydrogenase activity. The distributions of noradrenaline and 5-hydroxytryptamine between the subcellular fractions from homogenates of dog hypothalamus were also determined. Most of the dopamine, in contrast to acetylcholine, occurred in the soluble supernatant fraction; the remainder was associated with the fractions rich in pinched-off nerve ending particles, but localization in any one fraction was not as sharp as that of acetylcholine. Evidence is presented that suggests that the dopamine occurs in a free or easily released form throughout cell cytoplasm.

THE ORIGIN OF THE ACETYLCHOLINE RELEASED SPONTANEOUSLY FROM THE GUINEA-PIG ISOLATED ILEUM

When the guinea-pig isolated ileum had been previously treated with the anticholinesterase, NN-diisopropylphosphodiamidic fluoride (mipafox), and attached to an isotonic lever loaded with 0.5 g, it released acetylcholine into Krebs solution gassed with a mixture of 95% oxygen and 5% carbon dioxide. The amount of acetylcholine spontaneously released depended on the duration of the rest period. Cocaine, procaine or cooling the preparation to 25 degrees C greatly reduced this spontaneous output of acetylcholine, thus providing evidence in support of nervous origin of the ester. Reduction of the calcium ion content of the Krebs solution to one-twentieth of its usual value or increase in the magnesium ion content four-fold, changes which inhibit the release of acetylcholine from somatic motor nerve-endings, inhibited the output of acetylcholine from the ileum. When all the calcium of Krebs solution had been replaced by strontium one-third of the control output of acetylcholine was obtained, but the smooth muscle of the guinea-pig ileum would not respond to drugs under these conditions. Strontium could thus partially substitute for calcium in nerves but not in muscle. Hemicholinium-3 (100 mug/ml.) inhibited the spontaneous release of acetylcholine and 400 mug/ml. of choline was required to reverse the inhibition. It is concluded that cocaine, procaine, cooling, reduction of calcium ion and increase of magnesium ion concentrations all reduce the spontaneous output of acetylcholine, which has its origin in the parasympathetic nerve-endings of the intramural nerve plexuses. Further, the hemicholinium experiments seem to justify the conclusion that the release of acetylcholine is reduced because synthesis is reduced.