Heinrich Langemann

A fluorometric micromethod for the simultaneous determination of serotonin, noradrenaline and dopamine in milligram amounts of brain tissue

A miniaturized method for the assay of serotonin, noradrenaline and dopamine in extracts from l.5 to 5 mg of brain tissue (rat and mouse) was developed. The method permitted quantification and spectral analysis of pmole amounts of the amines. The method is derived from the solvent extraction technique and uses the principles of the trihydroxyindole and o-phthaldialdehyde methods for the development of fluorophores. The increase in sensitivity was accomplished mainly by volume reduction accompanied by changes of reagent concentrations. The small size of the tissue pieces requires a standardized dissection technique for the control of topographical variations. The problem of an appropriate reference system for the calculation of concentrations was also studied in detail. Protein weight was judged superior to wet weight for this purpose. The method was tested in a series of amine determinations on various areas of rat and mouse brain. Some examples of amine determinations as well as spectral analyses in various areas of single mouse brains are discussed.

The influence of ovariectomy, estrogen, and progesterone on the catecholamine content of hypothalamic nerve cells in the rat

Abstract In female rats the intensity of the catecholamine fluorescence was measured in nerve cell bodies of tubero-infundibular neurons by microfluorimetry, and the serum LH and FSH levels were determined. Ovariectomy interrupted the typical sequence in the frequency distributions of relative fluorescence intensity of the normal estrous cycle. A frequency distribution comparable to the type of diestrous day 2 was observed between 3 and 7 weeks after ovariectomy together with an LH level similar to diestrous day 2 but an FSH level higher than during the cycle. Ten μg of estradiol dipropionate caused a shift of the frequency distribution which then resembled the type of diestrous day 1, and a fall of LH and FSH levels. Very high doses were less effective in both respects. Effects of progesterone depended on whether it was administered with or without estrogen. The findings further support the hypothesis of a functional relationship between different states of activity of these tubero-infundibular neurons and the control of gonadotropin secretion.

Monoamines in the brain under the influence of muscimol and ibotenic acid, two psychoactive principles of amanita muscaria

The concentrations of noradrenaline, dopamine and serotonin were measured in the brain of male albino mice and rats after intraperitoneal injections of muscimol, ibotenic acid or LSD. All three drugs induced a generalized increase of serotonin. When muscimol was administered to rats after pretreatment with p-chlorophenylalanine, a serotonin synthesis inhibitor, the serotonin concentration was still increased in midbrain and hypothalamus. Muscimol also caused a reduced accumulation of 5-hydroxyindoleacetic acid in rats pretreated with probenecid. There were differences in the action of the three compounds on the catecholamine concentration. Muscimol and LSD caused a decrease of the catecholamines. Ibotenic acid increased the catecholamine concentration. Certain topographical differences were noted.The increase in the serotonin concentration in the hypothalamus and midbrain after muscimol may be due to a reduced turnover of serotonin. An increase in serotonin concentration and a decrease of 5-hydroxyindolacetic acid in the rat brain are effects observed also with other psychotomimetic drugs such as LSD or psilocybin.

Response of nigral dopamine neurons to acute and prolonged morphine treatment

The effects of morphine and acute exposure to cold on nigral dopamine (DA) neurons and possible interactions with cholinergic systems were studied by histochemical microfluorimetry in normal and partially morphine-tolerant mice. Morphine (40 mg/kg), cold (4 degrees C), nicotine (1 mg/kg) and physiostigmine (0.25 mg/kg) elicited a rapid rise and subsequent decrease in the fluorescence intensity of DA nerve cells with certain differences in time course. Fastest changes with a peak at 5 min, a marked subsequent drop below control levels and return towards control intensity after 40 min were seen after physostigmine. Antagonisms between various treatments were noted. DA responses correlated well with the time course of behavioural effects, especially after physostigmine. After 3 1/2 days of morphine treatment, the locomotor and analgesic effects of the drug were reduced. At this stage, the initial increase in fluorescence intensity after morphine and the biphasic pattern caused by physostigmine were delayed without any change in response magnitude. Responses to cold and nicotine remained unaltered both in magnitude and time course. Thus, partial tolerance affected the response of nigral DA neurons to some but not all funtional conditions and thereby markedly changed the interaction with cholinergic systems. The difference between physostigmine and nicotine suggests that neuronal circuits including mustcarinic mechanisms are possibly more susceptible to alteration.SummaryThe effects of morphine and acute exposure to cold on nigral dopamine (DA) neurons and possible interactions with cholinergic systems were studied by histochemical microfluorimetry in normal and partially morphinetolerant mice. Morphine (40 mg/kg), cold (4°C), nicotine (1 mg/kg) and physiostigmine (0.25 mg/kg) elicited a rapid rise and subsequent decrease in the fluorescence intensity of DA nerve cells with certain differences in time course. Fastest changes with a peak at 5 min, a marked subsequent drop below control levels and return towards control intensity after 40 min were seen after physostigmine. Antagonisms between various treatments were noted. DA responses correlated well with the time course of behavioural effects, especially after physostigmine.After 3 1/2 days of morphine treatment, the locomotor and analgesic effects of the drug were reduced. At this stage, the initial increase in fluorescence intensity after morphine and the biphasic pattern caused by physostigmine were delayed without any change in response magnitude. Responses to cold and nicotine remained unaltered both in magnitude and time course. Thus, partial tolerance affected the response of nigral DA neurons to some but not all functional conditions and thereby markedly changed the interaction with cholinergic systems. The difference between physostigmine and nicotine suggests that neuronal circuits including muscarinic mechanisms are possibly more susceptible to alteration.

The Uptake of Serotonin by Central Neurons Normally Containing Catecholamines

Publisher Summary The chapter focuses on the specificity of the amine uptake mechanism of central catecholamine containing neurons at the level of the cell membrane. Amines are localized histochemically by means of the fluorescence method. The uptake of 5-HT is influenced by amphetamine and cocaine in the same way as that of catecholamines by the same neurons. Central catecholamine neurons situated outside the blood–brain barrier can take up both exogenous catecholamines and 5-HT from the circulation in vivo, after they have been depleted by reserpine. The parallel influence of amphetamine and cocaine on the uptake of catecholamines and 5-HT by these neurons strongly suggests that at the level of the cell membrane, a similar mechanism is involved in the uptake of these amines.