Annica Dahlström

Demonstration and mapping out of nigro-neostriatal dopamine neurons

Abstract In normal rats dopamine-storing nerve terminals are found in the neostriatum (= the caudate nucleus + putamen) and dopamine-containing nerve cells in the substantia nigra, mainly in the pars compacta. After electrolytic lesions in the substantia nigra or the internal capsule the histochemical fluorescence and the dopamine content of the neostriatum were markedly reduced. Removal of the neostriatum produced an increased fluorescence of the dopamine nerve cells of the substantia nigra and of their axons central to the lesion. These axons ascend as a nerve tract in the internal capsule towards the neostriatum. The data give strong evidence for the existence of nigro-neostriatal dopamine neurons, which probably contain most or all of the dopamine present in the neostriatum.

Localization of monoamines in the lower brain stem.

Histochemische und pharmakologische Experimente sprechen stark dafür, dass Dopamin, Noradrenalin und 5-Hydroxitryptamin im Hirnstamm der Ratte in drei Typen von Nervenzellen und Endsynapsen gespeichert werden.

Effect of colchicine on transport of amine storage granules in sympathetic nerves of rat

Abstract Local application of colchicine to adrenergic ganglia and axons seems to interrupt the fast proximo-distal transport of amine storage granules. This effect may be due to destruction of neurotubules, which possibly take part in granular transport.

A functional effect of dopamine in the nucleus accumbens and in some other dopamine-rich parts of the rat brain

Dopamine (5 to 50 Μg) applied bilaterally to the nucleus accumbens of reserpine-nialamide pretreated rats produced a marked dose-dependent rise in coordinated locomotor activity, devoid of stereotypies such as gnawing, rearing and licking seen after dopamine application (50 Μg) to the neostriatum. The locomotor activity was completely blocked by pimozide, but not by phenoxybenzamine. The effects of apomorphine or d-noradrenaline were similar to those of dopamine. In contrast, l-noradrenaline produced a “convulsive” syndrome devoid of coordinated locomotor activity, and this convulsive syndrome could be completely blocked by phenoxybenzamine but not by pimozide. Release of endogenous dopamine by d- or l-amphetamine (10 and 50 Μg) in the nucleus accumbens produced a rise in coordinated activity, the d-isomer was about 4 times as potent as the l-isomer, and the effect of the d-isomer was blocked completely by α-methyltyrosine. Bilateral application of trifluoperazine (2.5 Μg) to the nucleus accumbens completely blocked the effect of systemically administered d-amphetamine (1.5 and 3.0 mg/kg), but similar application to the area of the central nucleus of the amygdala or the neostriatum was much less effective. Partial protection of the endogenous dopamine stores against the depleting action of reserpine by local application of metatyramine to the nucleus accumbens resulted in a higher level of basal activity than in control animals. Application of dopamine or noradrenaline to the area of the central nucleus of the amygdala or to the olfactory tubercles did not lead to any consistent changes in locomotor activity.The nucleus accumbens and olfactory tubercles contained most of the dopamine in the limbic forebrain, with noradrenaline more evenly distributed.These data suggest that the nucleus accumbens plays an important role in the locomotor activity in rats.

Effects of tyrosine hydroxylase inhibition on the amine levels of central monoamine neurons

Abstract As shown by both histochemical and biochemical methods, the methyl ester of α-methyl- p -tyrosine (H 44/68, 500 mg/kg i.p.), an inhibitor of the tyrosine hydroxylase, causes the catecholamines but not the 5-hydroxytryptamine in rat brain and spinal cord to disappear almost completely in 24 hours. There were no significant differences between the various regions in rate and degree of the depletion of the terminals and cell bodies. After transection the loss of noradrenaline from the spinal cord was prevented below but not above the lesion showing the importance of the impulse flow for the disappearance of the transmitter. A marked recovery was seen in all terminals and cell bodies after 48 hours. The reappearance was somewhat faster in the cell bodies suggesting that the tyrosine hydroxylase is formed in them.

Effects of two mitosis inhibitors (colchicine and vinblastine) on the distribution and axonal transport of noradrenaline storage particles, studied by fluorescence and electron microscopy.

SummaryThe lumbar sympathetic ganglia and the interganglionic interconnecting nerves of untreated rats and rats treated with Colchicine (COL) or Vinblastine (VIN) were studied with the help of the Falck-Hillarp fluorescence technique and electron microscopy. Both in untreated and drug treated rats there was a good correlation between the distribution of noradrenaline (NA) specific fluorescence and granular vesicles supporting the previous view that the granular vesicles represent the main intraneuronal NA storage sites. The granular vesicles were present both in the cell bodies—mainly in the peripheral part of the cytoplasm— and in the axons of untreated rats. After local application of COL or VIN on the ganglia there was a marked increase in fluorescence intensity and number of granular vesicles in many cell bodies. Often increased number of granular vesicles were found in the neighbourhood of the Golgi apparatus, in which region only few such vesicles are found in untreated rats. In some cell bodies high numbers of granular vesicles could be found all over the cytoplasm.When applied locally to axons the mitosis inhibitors caused a marked accumulation of fluorescence and granular vesicles—and other cell organelles like mitochondria and tubules of the endoplasmic reticulum-proximal to the site of application.A prominent feature both in cell bodies and axons of drug treated rats were large bundles of neurofilaments running through the cytoplasm. In the axons these filaments were often localized to the central part of the axon and surrounded by vesicles and tubules. Microtubules, on the other hand, which are rather numerous in cell bodies and axons of untreated rats seemed to be reduced in number after COL or VIN treatment, especially in those axons in which large amounts of subcellular organelles had accumulated.The present findings are discussed with respect to intraneuronal transport of NA and possible mechanisms behind this transport. It is suggested that the accumulation of fluorescence and granular vesicles after application of mitosis inhibitors is due to an interruption of the centrifugal transport of NA granules. The increased numbers of granular vesicles in the neighbourhood of the Golgi apparatus suggest that granular vesicles are produced in this part of the cytoplasm. This does not exclude a local formation of granular vesicles in other parts of the neuron. Furthermore, the possibility is discussed that the interruption of the transport is related to the increased number of neurofilaments and a possible decrease or disarrangement of microtubules. This discussion is based on previous suggestions that microtubules are involved in intracellular transport mechanisms and on recent findings that COL and VIN bind to proteins specific for microtubules.

Mapping out of catecholamine and 5-hydroxytryptamine neurons innervating the telencephalon and diencephalon

Abstract In previous investigations a large nigro-neostriatal dopamine (DA) neuron system has been characterized (1, 2). Also the hypothalamus, the preoptic area and the limbic system are innervated by ascending catecholamine (CA) neuron systems which degenerate after destruction of the CA cell groups in the mesencephalon (3). In this paper additional experimental evidence for the presence of ascending CA and 5-hydroxytryptamine (5-HT) neuron systems from the lower brain stem will be given consisting of changes in amine levels after different types of lesions in the prosencephalon (telencephalon plus diencephalon).

A METHOD FOR THE DEMONSTRATION OF ADRENERGIC NERVE FIBRES IN PERIPHERAL NERVES.

SummaryThe adrenergic nerve fibres running from the ganglia to the innervated tissues usually have too low a content of noradrenaline to be clearly visualized with the histochemical fluorescence method of Falck and Hillarp. They can easily be demonstrated, however, as early as 24 hours after axotomy (crushing or constriction of the nerves) due to the rapid accumulation of what is probably noradrenaline taking place proximally to the lesion. The fibres can be visualized even more clearly if axotomy is combined with the administration of l-dopa and with monoamine oxidase inhibition. In this way the presence, distribution and direction of adrenergic fibres can be directly studied in peripheral nerves.

Effects of the amphetamine group on intraneuronal brain amines in vivo and in vitro.

SIR,-Previous studies have shown that (+)-amphetamine in large doses causes a decrease in the brain content of noradrenaline (Smith, 1965). The present investigation was made to study the action of (+)-amphetamine at the cellular level with the help of the histochemical fluorescence method of Hillarp & others. The existence of central dopamine, noradrenaline and 5-hydroxytryptamine (5-HT) neurones has recently been demonstrated by this technique. These neurones have been shown to contain specific mechanisms for uptake and storage of the amines. They have an uptake mechanism, probably localized at the level of the cell membrane and sensitive to, for example, desipramine or cocaine (see review by Hillarp, Fuxe & Dahlstrom, 1965). Furthermore, they possess a reserpine-sensitive storage mechanism localised in specific granules. Single injections (i.p.) of (+)-amphetamine (5-60 mg/kg), (+)-amphetamine (1 5-60 mg/kg), methamphetamine (30 mg/kg) and benzylamphetamine (30 mg/kg) have been given to male, albino rats (Sprague-Dawley, 200-300 g). The animals were killed at 1,2 or 3 hr after theinjection. Pieces from all parts of the brain were dissected, freeze-dried and treated with formaldehyde gas (Dahlstrom & Fuxe, 1964). Fluorescence microscopic examination showed that (+)-amphetamine, 15-60 mg/kg, caused a fairly marked to marked decrease in number and intensity of the very fine catecholamine (mainly noradrenaline) terminals in, for example, the neocortex, the gyrus cinguli and the formatio reticularis of the lower brain stem. The fine to fairly thick catecholamine terminals of the hypothalamus, on the other hand, remained unaffected even with the higher doses. The dopamine and ~ H T terminals exhibited a normal appearance after all doses except with 60 mg/kg. After this dose, the dopamine terminals showed a distinct decrease in their amine contents. Somewhat less marked changes occurred after (&)-amphetamine and methamphetamine, while benzylamphetamine did not cause any definite decrease in the intraneuronal amine levels of the noradrenaline terminals. These results are supported by in vitro studies on the central monoamine neurone with brain slices (for technical details, see Hamberger & Masuoka, 1965). Noradrenaline terminals in brain slices from neocortex after preincubation with noradrenaline, 10 pg/ml, and rinsing were markedly decreased in

CENTRAL MONOAMINE NEURONS

Publisher Summary This chapter discusses the chemistry, histochemistry, specificity, and sensitivity of central monoamine neurons. The first step in the fluorescence reaction in the case of catecholamines (CA) is a condensation, resulting in the formation of a 6,7-dihydroxy-l,2,3,4-tetrahydroisoquinoline. Under the mild conditions used, the great activation of the 3-OH group is required for this condensation to be achieved and the catecholamines must obviously be either primary or secondary amines. Their 3-0-methylated and acid metabolites therefore do not react. The next step is a quite unexpected protein-promoted dehydrogenation, which gives the final fluorescent product, a 6,7-dihydroxy-3,4-dihydroisoquinoline.In the case of a secondary amine, this dehydrogenation gives rise to a quaternary 3,4-dihydroisoquinoline and requires more severe reaction conditions. Primary and secondary catecholamines can, thus, be differentiated from each other histochemical in a simple manner. The fluorescent product, 6-hydroxy-3,4-dihydro-β-carboline, has an emission spectrum with a peak about 50 mμ higher than that of the fluorescent product formed from CA.