[Effect of neurotropic drugs on the excitability of the structures of the striopallidal complex]

The results of investigations into the effect of microinjections of a number of adrenocholino- and dophaminergic agents on excitability of the pale globe, caudate nucleus and shell are reported. The non-uniformity of the effects produced by the agents of the mediator type action is established both in different segments and in individual zones of the extrapyramidal system with continuous concurrent antagonism between the mimetics and the corresponding blocking agents. The presence of alpha- and beta-adrenoreceptors and also of M- and N-cholinoreceptors in the structures of the striopallidal complex is suggested.

The beta-adrenergic responses in isolated splenic capsule area of several species of animals

In isolated splenic capsules of mouse, rat, guinea pig, rabbit, cat and dog, either a single or a cumulative dose of l- and dl-isoproterenol at a concentration higher than l0(-9) M, induced a relaxation which was inhibited or blocked with pretreatment of 10(-5) M propranolol. At a concentration of 5 x 10(-6) M to 10(-5) M 1- and dl-isoproterenol, an inverse contraction was induced, and such response was prevented or reversed to one of relaxation in the presence of 10(-5) M phentolamine. Application of 10(-5) M epinephrine produced a strong contraction and such was reversed to one of relaxation after addition of 10(-4) M phentolamine. This relaxation was reduced or blocked with pretreatment of 10(-5) M propranolol. Thus, it was confirmed that both alpha- and beta-receptors exist in the splenic capsule area of these different species.

Changes in adipocyte beta-adrenergic receptor of cold-acclimated rats

The changes in the number and affinity of binding sites in the beta-adrenergic receptors of rat white adipocytes after cold exposure were studied with the aid of (p)-[3H]dihydroalprenolol. One day cold exposure did not change the number and affinity of binding sites in beta-adrenergic receptors. Chronic exposure of rats to cold (5 degrees C) for 1 and 4 weeks significantly decreased the affinity of beta-adrenergic receptors without any alteration in the number of binding sites. Such changes in the binding affinity observed in cold-acclimated rats (4 weeks, 5 degrees C) remained for 18 hr after these animals were transferred to a warm environment of 25 degrees C. The decreased affinity of binding sites in beta-adrenergic receptor induced by cold acclimation could not explain the enhanced metabolic response of cold-acclimated animals to noradrenaline.

Direct characterization of beta-adrenoceptors in membranes of immature red blood cells from rats

By means of the radioactive antagonist ligand (3H)(-) dihydroalprenolol (DHAP) specific binding sites were identified in membrane preparations from red blood cells from rats. These specific sites were characterized as beta-adrenoceptors because of the following reasons: Specific binding of DHAP (in contrast to unspecific binding) was dependent on temperature and time of incubation. Furthermore, specific binding of DHAP showed saturability, temperature-dependent reversibility and high affinity (KD-value of DHAP = 6.51 nM). Specific binding of DHAP was competitively inhibited by beta-adrenergic antagonists (pindolol greater than alprenolol greater than or equal to propranolol greater than practolol) and agonists (isoprenaline greater than adrenaline). The (-) enantiomers of pindolol and isoprenaline showed pronounced higher affinities for the receptor sites than the respective (+) enantiomers. The receptor density in the membrane preparations (pmoles/mg protein) was strongly dependent on the degree of reticulocytosis: The Bmax-values increased more than 4 to 5 fold without alteration of the respective KD-values when reticulocyte counts were enhanced from 3 to 80% treatment of the animals with increasing doses of acetyl phenylhydrazine.

Influences on the density of beta-adrenergic receptors in the cornea and iris--ciliary body of the rabbit

By measurement of the specific binding of 3H-dihydroalprenolol, the densities of beta-adrenergic receptors on membranes prepared from homogenized corneas and iris--ciliary bodies of rabbits were studied. Sympathetic denervation, as a result of subconjunctival treatment with 6-hydroxydopamine, causes an increase in the density of beta-adrenergic receptors in membranes prepared from the ipsilateral iris--ciliary body but not the cornea. Topical treatment with epinephrine for 5 days causes a decrease in the density of beta-adrenergic receptors in membranes prepared from cornea and iris-ciliary body, whereas similar treatment with timolol causes an increase in the density of beta-adrenergic receptors. In the cornea, the decrease in receptor density that occurs following in vivo treatment with epinephrine is associated with a decreased ability to synthesize cyclic AMP, whereas the increase in receptor density that occurs following in vivo treatment with timolol is not associated with an altered ability to synthesize cyclic AMP. Our results indicate that the density of beta-adrenergic receptors in the anterior segment of the eye is inversely related to the level of adrenergic stimulation to the tissue but that the ability of a tissue to synthesize cyclic AMP does not necessarily parallel the change in receptor density.

The beta-adrenergic receptor of newborn mouse skin

Binding of the potent beta-adrenergic antagonist [125I]iodohydroxybenzylpindolol ([125I]IHYP) to particulate preparations from newborn mouse skin was characterized. A number of criteria were used to establish that binding occurred to specific, high affinity beta-adrenergic receptors in the skin preparations. Thus specific binding (that displaced by 10 micrometer concentrations of the beta-adrenergic antagonist (-)propranolol) reached equilibrium in 15--20 min, was saturable (ligand concentration for half-maximal saturation, 0.25 nM) and freely reversible. Stereoselectivity of binding was demonstrated by the observation that displacement of [125I]IHYP by (-)propranolol occurred at concentrations at least 100 times lower than with (+)isoproterenol. Displacement was also observed with the beta-adrenergic agonists (-)isoproterenol, (-)epinephrine and (-)norepinephrine, but not with the alpha-adrenergic antagonist phentolamine.

Alpha-adrenergic receptors in rat myocardium. Identification by binding of [3H]dihydroergocryptine

[3H]Dihydroergocryptine ([3H]DHE) binds to sites in membranes derived from rat myocardium that have the characteristics expected of alpha-adrenergic receptors. The binding is saturable with 41 fmol [3H]DHE bound per mg of protein and of high affinity with KD = 2.9 nM. The binding is rapid and readily reversible. Adrenergic agonists compete with [3H]DHE for binding in the order: epinephrine greater than norepinephrine greater than isoproterenol; and adrenergic antagonists compete for binding in the order: phentolamine greater than propranolol. For comparison, (-)[3H]dihydroalprenolol [(-)[3h]dha] was used to bind to sites in the same membrane preparations having characteristics of beta-receptors. The number and affinity of beta-receptors were quite similar to those of the alpha-receptors with 46 fmol (-)[EH]DHA per mg protein bound at saturation and KD = 2.5 nM. These techniques allowed identification of both beta- and alpha-adrenergic receptors in membranes derived from isolated atria, right ventricular free walls, and left ventricles including interventricular septa. This is the first report documenting direct identification of myocardial alpha-receptors by radioligand-binding techniques and complements the literature previously reporting myocardial inotopic and electrophysiological responses to alpha-adrenergic stimulation.

Histochemical labeling of beta-adrenergic receptors in the mouse central nervous system by 9-amino-acridin propranolol

A new fluorescent beta-adrenergic antagonist, 9-amino-acridin propranolol (9-AAP), was administered intravenously to living mice. In the cerebral cortex, the highest concentration of 9-AAP was noted in the hippocampal formation, where it distinctly labeled the hippocampal pyramidal cell layer and the granule cell layer of the dentate gryus. High uptake occurred in the pyramidal cell layer of the piriform cortex. In the neocortex, fluorescence was less dense and more diffuse but confined to the basal layers. A similar pattern was observed in the basal layers of the cingulate cortex, but an additional high-density dotted fluorescence labeled its layer II. In the cerebellar cortex, 9-AAP was localized within the Purkinje cell layer. In the spinal cord, the highest density of fluorescence was observed in the nuclear collections of alpha-motoneurons. The findings were similar to those observed in the central nervous system of the rat and support the reproducibility of the method. 9-AAP may be used in vivo as a fluorescent probe to map out the central beta-adrenergic receptor system.

The response of lymphatic smooth muscles to vasoactive substances

A study was made of the isotonic response of bovine mesenteric lymphatics to several physiological vasoactive substances. Contractions of lymphatic smooth muscles were induced by serotonin (5-HT), prostaglandin F2alpha (PGF2alpha), noradrenaline (NA), histamine, dopamine and acetylcholine (ACh). The smooth muscles were particularly sensitive to 5-HT. Excepting PGF2alpha no other substances could equal 5-HT in the magnitude of the maximum response. The majority of 5-HT receptors seemed to be the D receptors. The decreasing order of the contractile responses was as follows: 5-HT greater than PGF2alpha greater than NA greater than histamine greater than dopamine greater than ACh. The contractile response to ACh was observed only in specimens involving valvular region. It was very likely that, in the lymphatics, there were 2 kinds of receptors for catecholamines, i.e. alpha and beta receptors, and the stimulation of the former induced smooth muscle contraction and that of the latter relaxation. A difference was noticed between the responses of valvular and intervalvular segments to NA. Relaxations of lymphatic smooth muscles were induced not only by isoproterenol but also by adenosine and adenine nucleotides. The decreasing order of the relaxant responses was as follows: ISP greater than adenosine greater than ATP greater than ADP greater cyclic AMP greater than or equal to AMP. The relaxant responses to adenine nucleotides tended to reduce with decrease in the number of high energy phosphates.

Localization of beta receptors in the anterior segment of the rat eye by a fluorescent analogue of propranolol

A fluorescent analogue of propranolol, 9-AAP, was injected intravenously in order to detect beta-adrenergic receptors in the anterior segment of the albino rat eye. Specific 9-AAP fluorescence was noted along cell membranes of the ciliary epithelium and to lesser extent in the walls of blood vessels in the ciliary processes and episclera at the limbus. The iris showed maximum 9-AAP binding in the region of the sphincter muscle. These data suggest that 9-AAP may label beta receptors in the anterior segment of the rat eye.

[Beta-adrenoreceptors on the surface membranes of lymphocytes and macrophages]

In experiments in vivo and in vitro on sensitized and intact guinea pigs and Wistar rats the effect of beta-adrenergic stimulants (adrenaline and izoproterenol) and a beta-adrenergic blocker (propranalol) on lymphocytolysis and the reaction of macrophage adherence inhibition was studied. Adrenaline and izoproterenol were shown to inhibit the antigen interaction with both sensitized and intact cells. Restoring the sensitivity of cells to the antigen, propranalol destroys the defensive action of adrenaline and isoproterenol.

Serotonin nerve terminals in the locus coeruleus of adult rat: a radioautographic study

Serotonin (5-HT) nerve terminals in the locus coeruleus (LC) of adult rat were visualized by high-resolution radioautography, in order to examine their distribution, fine structural features and intimate relationships with norepinephrine neurons. In animals pretreated with a monoamine oxidase inhibitor, prolonged intraventricular perfusion of 10(-4) M [3H]5-HT resulted in a specific identification of most if not all 5-HT axonal varicosities in LC. These terminals were equally distributed between the dorsal and ventral divisions of the nucleus. Their density was approximated at 10(7) per cu.mm within the middle third of the LC. In electron microscope radioautographs, the labeled 5-HT varicosities averaged 0.9 micron in diameter. They all exhibited a distinctive storage organelle, in the form of microvesicles and microcanaliculi (15-25 nm in diameter) partly filled with electron-dense material and usually aggregated in association with several large dense-core vesicles. While this finding of intrinsic morphological characteristics appeared compatible with a special cellular origin or regional differentiation, it was also suggestive of particular functional properties and/or mode of action. In a sample comprised of some 500 sectional profiles from labeled 5-HT varicosities in LC, a small proportion only (less than 10%) exhibited morphologically defined synaptic junctions. These rare contacts were invariably made with dendritic processes and never observed on the noradrenergic perikarya. It is therefore concluded that, in the LC, non-synaptic as well as synaptic mechanisms might be involved in the modulation and transneuronal regulation of norepinephrine neurons by 5-HT afferents.