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Biomedical subjects

K Starke

Publications and source records attributed to K Starke.

At least 235 records · Page 13Linked to original sources
PubMed1981

Presynaptic receptors of central catecholamine neurones.

The article summarizes recent investigations on presynaptic alpha-adrenoceptors, opiate receptors and GABA receptors of central noradrenaline neurones, and on presynaptic dopamine receptors, opiate receptors and GABA receptors of central dopamine neurones. Pharmacological properties of the receptors, their location, and the steps linking receptor activation to changes in catecholamine release are discussed. In spite of a proliferation of research, there are large gaps in our knowledge of, in particular, GABA receptors and catecholamine release as well as opiate receptors and dopamine release.

Action Potentials↗
PubMed1980

Antagonist/agonist-preferring alpha-adrenoceptors or alpha 1/alpha 2-adrenoceptors?

Yohimbine and some stereoisomeric alkaloids inhibited the binding of 3H-clonidine and 3H-WB-4101 to rat cerebral cortex membranes. Rauwolscine and yohimbine had much higher affinity to the 3H-clonidine than to the 3H-WB-4101 site, whereas the reverse was true for corynanthine. The results indicate that the 3H-clonidine site is an alpha 2-adrenoceptor and not an agonist-selective site whereas the 3H-WB-4101 site is an alpha 1-andrenoceptor and not an antagonist-selective site.

Adrenergic alpha-Agonists↗
PubMed1980

Selective inhibition by amezinium of intraneuronal monoamine oxidase.

Intra- and extraneuronal compartments of rat hearts were selectively labelled by perfusion with 3H-noradrenaline in the presence of corticosterone 87 microM or cocaine 30 microM, respectively. The subsequent outflow of 3H-compounds was examined. As little as 1 nM amezinium diminished the outflow of intraneuronally formed 3H-DOPEG. This effect was antagonized by cocaine. Amezinium 1 microM was necessary to diminish the outflow of extraneuronally formed 3H-DOPEG. This effect was not counteracted by corticosterone. The results indicate that amezinium is both a potent and, at low concentrations, selective inhibitor of intraneuronal MAO.

Animals↗
PubMed1980

Modulation by endogenous dopamine of the release of acetylcholine in the caudate nucleus of the rabbit.

Slices of the caudate nucleus of rabbits were preincubated with 3H-choline and then superfused. Stimulation by electrical pulses at 3 Hz or by 25 mmol/l potassium elicited an increase in tritium outflow which was calcium-dependent and, in the case of electrical stimulation, tetrodotoxin-sensitive. The dopamine receptor agonist apomorphine (0.01-1 mumol/l) decreased, whereas the antagonist haloperidol increased the electrically evoked overflow of tritium. Nomifensine and cocaine, used at concentrations known to inhibit the re-uptake of dopamine, also reduced the evoked overflow of tritium, and this reduction was antagonized by haloperidol. Combined pretreatment with reserpine and alpha-methyltyrosine methylester (alpha-MT), which lowered dopamine levels by 99.5%, increased the electrically evoked overflow, as did bretylium which is shown here to block action potential-induced release of dopamine. The facilitation by haloperidol and bretylium as well as the inhibition by nomifensine and cocaine were diminished or abolished after pretreatment with reserpine plus alpha-MT. Apomorphine decreased, and haloperidol increased, the potassium-evoked overflow of tritium; the effects were not changed by tetrodotoxin. The results indicate that the striatal dopamine receptors which, when activated, depress the release of acetylcholine, are akin to the D-2 type. Endogenous dopamine also acts on the receptors as shown by several manipulations with known effects on dopaminergic transmission. A large fraction of these dopamine receptors may be located on the cholinergic axon terminals.

Acetylcholine↗
PubMed1980

Interneurones are probably not involved in the presynaptic dopaminergic control of dopamine release in rabbit caudate nucleus.

Slices of rabbit caudate nucleus were preincubated with 3H-dopamine and then superfused. The influence of apomorphine and haloperidol on the overflow of tritium evoked by 20 mmol/l potassium was investigated in the presence and in the absence of tetrodotoxin. The potassium-evoked overflow was largely calcium-dependent and consisted mainly of 3H-dopamine. The dopamine receptor agonist apomorphine 0.01-1.0 mumol/l reduced, whereas the antagonist haloperidol 0.1 mumol/l enhanced the potassium-evoked overflow of tritium. The effects of apomorphine and haloperidol were as pronounced in the presence as in the absence of tetrodotoxin 0.3 mumol/l. It is concluded that the presynaptic dopaminergic modulation of dopamine release is not mediated by a tetrodotoxin-sensitive interneuronal pathway.

Action Potentials↗
PubMed1980

gamma-Aminobutyric acid and postganglionic sympathetic transmission in the pulmonary artery of the rabbit.

1 The effect of gamma-aminobutyric acid (GABA) on postganglionic sympathetic neurotransmission was studied in strips of the rabbit pulmonary artery. The strips were preincubated with 3H-noradrenaline and then superfused with 3H-amine-free medium. They were stimulated either electrically at 2 Hz, or by 60 mM potassium, or by 1 microM tyramine. 2 GABA (1 - 1000 microM) did not change the basal outflow of tritium, but decreased the electrically evoked overflow as well as the contractile response. GABA 1 microM decreased the evoked overflow by 12%, and GABA 1000 microM, by 42%. The effect of GABA was not changed by yohimbine, propranolol, cocaine, corticosterone, or indomethacin. It was not antagonized by picrotoxin or bicuculline methiodide. GABA 100 microM also slightly reduced the potassium-evoked overflow of tritium but did not change the tyramine-evoked overflow. 3 The results show that, in the pulmonary artery of the rabbit, GABA inhibits the release of noradrenaline. Its effect is independent of alpha- and beta-adrenoreceptors and is not mediated by prostaglandins. The effect may be due to activation of presynaptic receptors which appear to differ from conventional GABA receptors inasmuch as they are insensitive to blockade by either picrotoxin or bicuculline.

Animals↗
PubMed1979

[Sexual experience and family planning among freshmen (author's transl)].

In the last few years, the number of freshmen who experienced their first sexual intercourse prior to college has increased. This is due to the first occurrence of sexual intercourse at an earlier age even among prospective students. The proportion of university students wishing to get married and to have children during their university years has substantially increased.

Adolescent↗
PubMed1978

Effects of prostaglandin E2, prostaglandin I2 and 6-keto-prostaglandin F1 alpha on adrenergic neurotransmission in the pulmonary artery of the rabbit.

Strips of the rabbit pulmonary artery were preincubated with 3H-noradrenaline and then superfused and stimulated electrically at 2 or 4 Hz. PGE2 and PGI2 reduced the stimulation-evoked overflow of total tritium and 3H-noradrenaline. PGI2 was about 10 times less potent than PGE2. High concentrations of 6-keto-PGF 1alpha also diminished the evoked overflow, but the effect was small. It is concluded that PGI2, in comparison with PGs of the E series, is a relatively weak inhibitor of noradrenaline release.

Animals↗