Aromatic L-amino acid decarboxylase in the rat brain: immunocytochemical localization in neurons of the brain stem

Extrinsic denervation elevates neuronal aromatic L-amino acid decarboxylase immunoreactivity in rat small intestine

In order to clarify further the neural control of digestive tract function, we have compared the neuronal localization of tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC) in rat small intestine. Immunoreactivity for TH was found in numerous varicose axons associated with neurons of the enteric plexuses and in axons within the circular muscular coat and the mucosal villi. Axons with AADC immunoreactivity had a similar distribution, but were sparser in the enteric plexuses and musculature than those containing TH. Chronic extrinsic denervation of a segment of intestine removed all TH-positive nerves from that region. By contrast, the intensity of AADC immunoreactivity was enhanced and more AADC-positive axons were visible than in adjacent intact areas of intestine. The AADC-positive axons appear to represent the intrinsic 'amine-handling' neurons rather than intrinsic tryptaminergic neurons or extrinsic dopaminergic neurons, and the effect on AADC activity of removing the extrinsic nerve supply suggests that this normally exerts some restraining influence on the metabolism of the 'amine-handling' population.

Evidence that dopaminergic sympathetic axons supply the medullary arterioles of human kidney

The ability of the kidney to excrete sodium appears to depend on release of dopamine from intrarenal sources. In the present study, we have used immunohistochemistry to examine the possibility that renal dopaminergic nerves constitute one of these sources. We found that the sympathetic axons supplying cortical structures in human kidney contain tyrosine hydroxylase-like immunoreactivity but lack DOPA decarboxylase-like immunoreactivity. By contrast, the vasa recta arterioles of the renal medulla are supplied by varicose tyrosine hydroxylase-positive nerve fibres, some of which also contain DOPA decarboxylase. As DOPA decarboxylase has been demonstrated in other situations to be a selective marker for dopaminergic terminal axons, our results suggest the innervation of renal medullary blood vessels in man by both noradrenergic and dopaminergic sympathetic nerves.

Functional interactions of 2-phenylethylamine and of tryptamine with brain catecholamines: implications for psychotherapeutic drug action

1. The relevance of trace amine research is outlined for PEA and T in the context of psychotherapeutic drug action, particularly in relation to the actions of MAO-inhibitor antidepressant drugs. 2. Evidence for the neuronal localization of these amines and their relationship to brain catecholamines is discussed with respect to possible co-localization with DA and their distribution within the nigro-striatal/striato-nigral system. 3. The results of recent experiments assessing the behavioural effects of prodrugs for PEA and T are described. The interactions of these compounds with MAO inhibitors are assessed and the actions of PEA prodrugs are discussed in relation to brain DA systems. 4. Recent evidence for functional decreases in beta-adrenergic receptors following chronic administration of MAO inhibitors is outlined. The lack of association of such effects with the percentage of MAO inhibition observed after these treatments indicates influences of these compounds (or metabolites) on factors other than MAO activity as mediators of these effects. The possible role of PEA (as a metabolite of PLZ) in this context is proposed. The possible involvement of PEA in emergent changes in beta-adrenergic receptors induced by chronic antidepressant drugs is hypothesized in relation to ongoing research.

Coexistence of catecholamine and methionine enkephalin-Arg6-Gly7-Leu8 in neurons of the rat ventrolateral medulla oblongata. Application of combined peptide immunocytochemistry and histofluorescence method in the same vibratome section

An overlapping distribution of catecholamine-containing cells and proenkephaline-A derived peptide-containing neurons have been identified in the rat medulla oblongata. However, it is not evident whether the coexistence of these bioactive substances occurs in the same neurons or not. Therefore, we examined the coexistence of catecholamine and methionine-enkephalin-Arg6-Gly7-Leu8 (MEAGL), a proenkephaline-A derived peptide, using a combination of histofluorescence and peroxidase-anti-peroxidase (PAP) immunohistochemical (modified formaldehyde-glutalaldehyde (Faglu)) methods on the same tissue sections. We found one third of A1/C1 catecholamine fluorescent cells show MEAGL-like immunoreactivity.

Aromatic L-amino acid decarboxylase activity of the rat retina is modulated in vivo by environmental light

Aromatic L-amino acid decarboxylase (AAAD) activity of rat retina is low in animals placed in the dark. When the room lights are turned on, activity rises for almost 3 h and reaches values that are about twice the values found in the dark. A study of the kinetics of the enzyme revealed that the apparent Km values for L-3,4-dihydroxyphenylalanine and pyridoxal-5'-phosphate were unchanged in light- and dark-exposed animals, whereas the Vmax increased in the light. Treating the animals with cycloheximide before exposure to light prevented the increase of enzyme activity. Immunotitration with antibodies to AAAD suggested that more enzyme molecules are present in the light than in the dark. When the room lights are turned off AAAD activity drops rapidly at first and then more slowly, suggesting that at least two processes are responsible for the fall of enzyme activity. Exposure to short periods of dark followed by light results in a rapid increase of AAAD activity. Mixing homogenates from light- and dark-exposed rats results in activity values that are less than expected, suggesting the presence of an endogenous inhibitor(s). These studies demonstrate that AAAD activity is modulated in vivo.

Immunohistochemistry of aromatic L-amino acid decarboxylase in the cat forebrain

The topographic distribution of aromatic L-amino acid decarboxylase (AADC)-immunoreactive (IR) neurons was investigated in the cat hypothalamus, limbic areas, and thalamus by using specific antiserum raised against porcine kidney AADC. The perikarya and main axons were mapped on an atlas in ten cross-sectional drawings from A8 to A16 of the Horsley Clarke stereotaxic plane. AADC-IR neurons were widely distributed in the anterior brain. They were identified in the posterior hypothalamic area, rostral arcuate nucleus of the hypothalamus, dorsal hypothalamic area, and periventricular complex of the hypothalamus, which contain tyrosine hydroxylase (TH)-IR cells and are known as A11 to A14 dopaminergic cell groups. AADC-IR perikarya were also found in the other hypothalamic areas where few or no TH-IR cells have been reported: the supramamillary nucleus, tuberomamillary nucleus, pre- and anterior mamillary nuclei, caudal arcuate nucleus, dorsal hypothalamic area immediately ventral to the mamillothalamic tract, anterior hypothalamic area, area of the tuber cinereum, retrochiasmatic area, preoptic area, suprachiasmatic and dorsal chiasmatic nuclei. We also identified them in the anterior commissure nucleus, bed nucleus of the stria terminalis, stria terminalis, medial and central amygdaloid nuclei, lateral septal nucleus, and nucleus of the diagonal band of Broca. AADC-IR neurons were localized in the ventromedial part of the thalamus, lateral posterior complex, paracentral nucleus and lateral dorsal nucleus of the thalamus, medial habenula, parafascicular nucleus, subparafascicular nucleus, and periaqueductal gray. Conversely, we detected only a few AADC-IR cells in the supraoptic nucleus whose rostral portion contains TH-IR perikarya. Comments are made on the relative localizations of the AADC-IR and TH-IR neurons, on species differences between the cat and rat, as well as on the possible physiological functions of the enzyme AADC.

Distributions of tyrosine hydroxylase-, dopamine-beta-hydroxylase-, and phenylethanolamine-N-methyltransferase-immunoreactive neurons in the brain of the hamster (Mesocricetus auratus)

Antibodies to the catecholamine synthetic enzymes tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT) were used in an immunohistochemical analysis of the brain of the golden hamster. The distributions and morphological characteristics of neurons displaying immunoreactivity to these enzymes were examined in sets of adjacent sections. Various novel groups of TH-immunoreactive neurons were found. A distinct feature observed in the hamster brain was the presence of a population of magnocellular multipolar neurons in the basal forebrain which displayed intense TH immunoreactivity. These cells were found predominantly in the vertical and horizontal limbs of the nucleus of the diagonal band of Broca and in the lateral preoptic area. Many small TH-positive cells were also found scattered in the deeper layers of the cortex in the hamster. The pericentral divisions of the inferior colliculus contained a large number of TH-immunoreactive neurons, and a few small bipolar cells in the lateral superior olive were also stained. A major cell group was found in the lateral parabrachial nucleus at the level of the locus ceruleus that displayed TH but not DBH immunoreactivity and was obviously separate from the TH- and DBH-positive cells of the locus ceruleus. Additional TH-positive cell groups were found along the seventh nerve, within the medial longitudinal fasiculus, in the nucleus raphe pallidus, and in the pars caudalis of the spinal trigeminal nucleus. The various catecholamine cell groups described by many people in the rat by use of histochemical and immunohistochemical techniques were also present in the hamster brain. These included the noradrenergic, TH- and DBH-immunoreactive cell groups of the pons and medulla. The hamster also displayed groups of medullary neurons displaying immunoreactivity to TH, DBH, and PNMT. These appeared similar in distribution and morphology to the adrenaline cell groups described in the rat. TH-immunoreactive cell groups in the olfactory bulb, hypothalamus, substantia nigra, and ventral tegmental area of the hamster appeared to correspond to the dopaminergic cells groups described in the rat and other species. In addition, as in the rat and cat, numerous TH-positive cells were found in the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, and the area postrema. These observations suggest that catechols may be present in neurons in the cortex, basal forebrain, auditory brainstem, and the parabrachial nucleus of the hamster. These studies also emphasize the need for caution in making generalizations regarding transmitter distributions across species.

Studies on dopamine-, tyrosine hydroxylase- and aromatic L-amino acid decarboxylase-containing cells in the rat diencephalon: comparison between formaldehyde-induced histofluorescence and immunofluorescence

The morphology, number and distribution of catecholaminergic neurons, as visualized either with the aluminum-catalysed formaldehyde method for catecholamines or with the immunohistochemical method for the catecholamine-synthesizing enzymes tyrosine hydroxylase and aromatic L-amino acid decarboxylase, respectively, were analysed within the rat dorsal hypothalamus, ventral thalamus and adjoining regions (A11 and A13 cell groups). Both polyclonal rabbit and monoclonal mouse tyrosine hydroxylase antibodies were used in elution-restaining and double-staining experiments, respectively. Some of the animals also received spinal injections of the fluorescent tracer True Blue in order to retrogradely label cells projecting to the spinal cord. With respect to the number and distribution of catecholaminergic neurons in the A11 and medial A13 cell groups, including the spinal-projecting subpopulation, the results obtained with the two methods were very similar, indicating that within these regions of the CNS the two methods in principle visualize identical cell populations. However, the catecholaminergic cells were distinctly larger and their processes appeared more extensive with the immunohistochemical method. Animals processed for immunohistochemistry exhibited a lower total number of retrogradely labelled cells in the A11 area than those analysed with aldehyde-induced fluorescence despite the fact that both methods revealed similar numbers of retrogradely labelled tyrosine hydroxylase-positive and catecholamine-containing cells, respectively. The reason for these discrepancies, which are probably of methodological nature, are discussed. While this study shows that the results obtained with the two methods within the A11 and medial A13 cell group are very similar and thus strengthens the earlier proposed concept of the organization of the diencephalospinal dopaminergic system, it also documents that in intermingling and nearby CNS regions there are cell bodies which cannot be demonstrated with the aldehyde fluorescence method, but which still contain tyrosine hydroxylase and/or aromatic L-amino acid decarboxylase-like immunoreactivity. One explanation is low levels of enzyme and/or dopamine combined with a comparatively low sensitivity of the histochemical method. Thus, neurons containing both enzymes are probably dopaminergic, even if catecholamine fluorescence cannot be demonstrated. Neurons containing tyrosine hydroxylase, but lacking both aldehyde induced fluorescence and aromatic L-amino acid decarboxylase, may also still be dopaminergic.(ABSTRACT TRUNCATED AT 400 WORDS)

Peptide- and transmitter-containing neurons in the mediobasal hypothalamus and their relation to GABAergic systems: possible roles in control of prolactin and growth hormone secretion

Indirect immunofluorescence histochemistry was used to study the relation among GABAergic, catecholaminergic, cholinergic, and peptidergic neurons in the rat mediobasal hypothalamus. By employing a direct double-labelling procedure using sheep antiserum against glutamic acid decarboxylase (GAD), mouse monoclonal and rabbit antibodies to neurotensin (NT) and rabbit antisera to tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), galanin (GAL), growth hormone-releasing factor (GRF), or somatostatin (SOM), it was demonstrated that GAD-positive fibers and terminals in the external part of the median eminence co-contained immunoreactivity for TH, NT, GAL or GRF, but not for SOM. In the internal part of the median eminence-infundibular stalk, GAD-positive/NT-, GAL-, and GRF-negative and GAD-positive/TH-positive fiber plexa were shown. When a recently developed direct triple-labelling procedure with biotin-conjugated mouse secondary antibodies in conjunction with diethylaminocoumarin (DAMC)-conjugated avidin was employed, presence of GAD/GAL/NT- as well as GAD/GRF/NT-containing varicosities could be demonstrated close to hypophysial portal vessels. In colchicine-pretreated animals, GAD was shown to coexist with TH, NT, or GAL in cell bodies in both the dorsomedial and ventrolateral domains of the arcuate nucleus, but with GRF only in the ventrolateral division. ChAT-positive neurons in the ventrolateral region were also TH-positive. In the ventrolateral arcuate nucleus, triple-labelling followed by elution-restaining showed GAD/NT/GAL/TH-immunoreactivities in the same cells. Similarly, double-labelling with two following elution-restaining steps showed several NT/GAL/GRF/TH-containing cell bodies in this part of the arcuate nucleus. GAD-positive cells in the anterior hypothalamic periventricular area and fibers in the pituitary neurointermediate lobe were also TH-positive. The results demonstrate complex patterns of storage of chemical messengers in neurons of the arcuate nucleus-median eminence complex. Possible neuroendocrine interactions of these systems in the control of prolactin and growth hormone secretion are discussed.

5-Hydroxytryptophan (5-HTP)-immunoreactive neurons in the rat brain tissue

We demonstrated the presence of 5-hydroxytryptophan (5-HTP), the immediate precursor of serotonin (5-HT), in the rat brain tissue using a glutaraldehyde-coupled immunohistochemical technique. The immunoreactivity of 5-HTP was intensified in the colchicine-pretreated rat. The distribution of labelled cells was the same as for 5-HT-immunoreactive cells, but they were fewer in number.

Effect of monofluoromethyldopa (MFMD) on trace amine levels

The concentrations of the trace amines, m-tyramine, p-tyramine, phenylethylamine and tryptamine, were measured in the striatum of the brain and in the kidney of adult rats treated with alpha-monofluoromethyldopa (MFMD), an inhibitor of aromatic amino acid decarboxylase. While MFMD decreased the levels of all four amines in the kidney, only phenylethylamine and tryptamine levels were decreased in the striatum compared to control. Striatal p-tyramine levels were not affected, while striatal m-tyramine levels were increased by MFMD. When the rats were injected with a monoamine oxidase (MAO) inhibitor before MFMD administration, similar changes in striatal and kidney trace amine levels were observed compared to MFMD alone.

Demonstration of immunohistochemical and immunochemical cross-reactivity of L-histidine and L-dopa decarboxylases using antibodies against the two enzymes

Both rat L-histidine decarboxylase (HDC) and guinea-pig L-DOPA decarboxylase (DDC) were shown immunohistochemically and immunochemically to react with anti-rat HDC antibody. No cross-reaction was observed in immunoprecipitation experiments, but both anti-rat HDC antibody and anti-rat DDC antibody immunostained neurons in the substantia nigra, raphe nucleus and locus coeruleus of guinea-pig brain. Moreover, on immunoblotting, anti-rat HDC antibody recognized not only rat HDC but also guinea-pig DDC, but not rat DDC. However, anti-rat DDC antibody showed no immunohistochemical or immunochemical cross-reactivity with rat HDC.

Depletion of striatal beta-phenylethylamine following dopamine but not 5-HT denervation

The effects of lesions of the substantia nigra (electrolytic 2 mA 10 sec, or 6-OHDA 2 or 8 micrograms) and of the midbrain raphé nuclei (electrolytic 2 X 1.0 mA 10 sec) at 7 days postlesion on striatal levels of beta-phenylethylamine, DA, DOPAC, HVA, 5-HT and 5-HIAA and on hypothalamic levels of beta-phenylethylamine, DA, NA, 5-HT and 5-HIAA were investigated. In the presence of deprenyl (2 mg kg-1 2 hr SC), both electrolytic and 6-OHDA-induced dopamine-depleting lesions of the nigra but not 5-HT-depleting lesions of the raphé nuclei resulted in a marked decrease in the accumulation of beta-phenylethylamine. The marked reduction in accumulation of striatal beta-phenylethylamine in response to lesions of the substantia nigra indicates that the intraneuronal compartment is a major site of striatal beta-phenylethylamine synthesis. An equivalent decrease (approximately 40%) in the accumulation of 5-HT was observed following electrolytic lesions of the substantia nigra or raphé nuclei after administration of L-5-HTP (200 mg kg-1 hr IP). As L-5-HTP at the dose employed in this study is taken up non-selectively by both DA- and 5-HT-containing neurones the loss of L-AAD following nigral and raphé lesions was apparently equivalent. These results indicate that depletion of beta-phenylethylamine may not be simply attributable to a general loss of L-AAD following lesions of monoamine-containing neurones and suggest either co-localisation of beta-phenylethylamine and DA or the existence of distinct beta-phenylethylamine-containing neurones.

The distribution of tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyltransferase immunoreactive neurons in the feline medulla oblongata

The distributions and morphological characteristics of neurons displaying immunoreactivity to the catecholamine synthetic enzymes tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT) were examined in adjacent sections of the feline medulla oblongata. TH-positive neurons were found in two bilaterally symmetrical columns in the ventrolateral and dorsomedial medulla. Within the ventrolateral medulla, TH-positive neurons were found within the lateral reticular formation throughout the entire rostrocaudal extent of the medulla. In the dorsomedial medulla, TH-immunoreactive perikarya were localized to the nucleus of the tractus solitarius including the commissural subnucleus, the dorsal motor nucleus of the vagus, and the area postrema. DBH-positive neurons had distributions and morphologies similar to those of the TH-immunoreactive cells with three exceptions: TH-positive neurons far outnumbered DBH-positive neurons in the area postrema; slightly greater numbers of TH-positive neurons were seen in the commissural nucleus of the tractus solitarius; and, caudal to the obex, only TH-positive neurons were seen within the dorsal motor nucleus of the vagus. PNMT-immunoreactive neurons were found in all the nuclear regions of the medulla where both TH- and DBH-positive neurons were seen. However, the PNMT immunoreactive perikarya had a somewhat more restricted distribution along the rostrocaudal axis. In the ventrolateral medulla, PNMT-positive cells extended rostrally only as far as the retrofacial nucleus and caudally only to the obex. Within the dorsomedial medulla, PNMT immunoreactive cells were found from just rostral to the area postrema to the medullary-spinal cord junction. These findings demonstrate that the distributions of TH, DBH, and PNMT immunoreactive perikarya in the medulla of the cat are generally similar to those seen in the rat insofar as these neurons are arranged in longitudinal columns in both species. However, significant differences exist with regard to the cytoarchitectonic borders within which immunoreactive perikarya can be found and the rostrocaudal extent of the PNMT-positive cell groups in these two species.

Aromatic L-amino acid decarboxylase in the rat brain: immunocytochemical localization during prenatal development

Immunocytochemically labeled cells containing the enzyme aromatic L-amino acid decarboxylase were localized in the brain of rat embryos at gestational age E15-E19. Cell groups that contained aromatic L-amino acid decarboxylase but lacked either the enzyme tyrosine hydroxylase or the indolamine serotonin were referred to as "D" groups. Anatomical landmarks, cytoarchitectonic structure and histochemical staining for acetylcholinesterase were used to delineate the position of "D" groups. In the E15 embryo three "D" groups existed. The first to appear, named D1, was located in the spinal cord and had been demonstrated before. A large "D" cell cluster was found in the walls of the central forebrain deep to the hypothalamic sulcus. This group distributed dorsally in the ventral dorsal thalamic region and ventrally in the dorsal hypothalamus. The rostral-most "D" group, D14, occurred in the ventral telencephalon just medial to fibers of the nigrostriatal projection. D14 was the smallest of the early groups. In E16 and E17 embryos dorsal di- and mesencephalic "D" groups were first detected. During the course of ontogeny a considerable increase of immunoreactive cells occurred and segregation of the large central forebrain cluster into several rostrally and laterally distributed "D" groups took place. Some "D" groups that occur in the adult brain were not present in the E19 embryo. This study provides a first report of the localization of several unique cell groups in the brain of rat embryos and their appearance at different stages of gestation. It also gives further support to the notion that variations of aromatic L-amino acid decarboxylase staining intensities may be characteristic of different monoamine neurons.

Dopaminergic and noradrenergic sympathetic nerves of the dog have different DOPA decarboxylase activities

We have compared the pattern of neural catecholamine fluorescence with that of immunoreactivity for the catecholamine-synthesizing enzymes tyrosine hydroxylase (TH) and DOPA decarboxylase (DDC) in dog atrium, which is innervated by noradrenergic nerves, and in dog kidney, which is thought to be supplied by dopaminergic nerves as well. In both tissues the distribution of nerves containing catecholamine fluorescence was similar to that of nerves exhibiting TH-like immunoreactivity. By contrast, DDC-like immunoreactivity was present in some (but not all) of the nerves associated with the intrarenal blood vessels, but was not detectable in any atrial nerves. High DDC activity provides further confirmation of the existence of sympathetic dopaminergic neurons supplying the kidney.

Inhibition of monoamine oxidase selectively in brain monoamine nerves using the bioprecursor (E)-beta-fluoromethylene-m-tyrosine (MDL 72394), a substrate for aromatic L-amino acid decarboxylase

(E)-beta-Fluoromethylene-m-tyrosine (FMMT) is a dual-enzyme-activated inhibitor of monoamine oxidase (MAO). The compound is not an inhibitor per se but is decarboxylated by aromatic L-amino acid decarboxylase (AADC) to yield a potent enzyme-activated irreversible inhibitor of MAO, (E)-beta-fluoromethylene-m-tyramine, which shows some selectivity for inhibition of MAO type A. Decarboxylation of FMMT was demonstrated in vitro using hog kidney AADC and in vivo in rats by the ability of alpha-monofluoromethyldopa (MFMD), a potent inhibitor of AADC, to prevent MAO inhibition produced by FMMT. In isolated synaptosomes, FMMT was decarboxylated by AADC, and, furthermore, the compound was actively transported into these isolated nerve endings. An active transport into the CNS has also been demonstrated in vivo by performing competition experiments with leucine. To demonstrate that FMMT is preferentially decarboxylated within monoamine nerves of the CNS, the nigrostriatal 3,4-dihydroxyphenylethylamine (dopamine) pathway of rats was unilaterally lesioned with 6-hydroxydopamine or infused with MFMD. Under these conditions, MAO inhibition produced by orally administered FMMT in the striatum ipsilateral to the lesion or infusion was markedly attenuated. Combination of FMMT with an inhibitor of extracerebral AADC, such as carbidopa, protected peripheral organs against the MAO inhibitory effects and concomitantly enhanced MAO inhibition in the CNS. Such combinations had a greatly reduced propensity to augment the cardiovascular effects of intraduodenally administered tyramine, when compared with FMMT given alone or with clorgyline, a selective inhibitor of MAO type A. The results obtained with FMMT suggest the possibility of achieving selective inhibition of MAO within monoamine nerves of the CNS and, further, suggest that combination of FMMT with an inhibitor of extracerebral AADC will reduce the propensity of this inhibitor to produce adverse interactions with tyramine.

The synthesis and metabolism of catecholamines in the spinal cord of the rat after acute and chronic transections

The capacity of the spinal cord of the rat to synthesize and metabolize catecholamines from injected L-DOPA, was tested at 10 and 100 days after a middle thoracic transection of the cord. There was no indication of even a minimal recovery of the capacity to synthesize noradrenaline in the caudal region of the transected cord. At 10 days after transection, the lumbar cord could synthesize 50% of the dopamine formed in the intact cord. At 100 days after transection the synthesis of dopamine in the transected cord was equal to that in the intact control animal. At both 10 and 100 days after transection, the dopamine synthesized from L-DOPA was efficiently metabolized to dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). As judged from the levels of gamma-aminobutyric acid (GABA) and glutamic acid (glutamate) present in the transected cord, no major metabolic derangement of the spinal cord tissue seemed to have been present at the times the experiments were done. It is concluded that dopamine can be efficiently synthesized and metabolized from its immediate precursor, L-DOPA, even in the absence of monoaminergic nerves. The results are discussed with reference to two main themes. The first, is the likelihood that in the therapeutic use of L-DOPA in states of chronic dopaminergic nerve degeneration (e.g. Parkinson's disease), the synthesis and metabolism of dopamine probably occurs throughout the entire central nervous system. The second, is the possible usefulness of L-DOPA to test for the relative intactness of spinal reflex circuities in the chronically spinalized animal.

Simple purification of aromatic L-amino acid decarboxylase from human pheochromocytoma using high-performance liquid chromatography

We purified aromatic L-amino acid decarboxylase (AADC) homogeneously and rapidly from human pheochromocytoma using high-performance liquid chromatography. HPLC with gel permeation and hydrophobic columns was highly effective, and the entire purification could be finished within 3 days. Purified AADC showed a single band with an Mr of 50,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and decarboxylated L-3,4-dihydroxyphenylalanine, L-5-hydroxytryptophan, and L-threo-3,4-dihydroxyphenylserine (a synthetic precursor of natural norepinephrine). Amino acid analysis of purified AADC was performed.

Distribution of neurons containing phenylethanolamine N-methyltransferase in medulla and hypothalamus of rat

Neurons immunocytochemically labeled with the adrenaline-synthesizing enzyme phenylethanolamine N-methyltransferase were mapped in the brain of rat pretreated with colchicine. In medulla, immunoreactive cells in the C1 and C2 groups were distributed in a more complex manner than described previously. C1 neurons were identified in the reticular formation of ventrolateral medulla and were organized into two populations: (1) a cell column extending throughout the ventrolateral medulla, and lying ventral to the ambiguus cell group and either dorsal to the precerebellar lateral reticular nucleus or interposed between its two subdivisions; (2) a rostral cell cluster forming medial to the column at caudal levels and enlarging close to and in parallel with the ventral surface of the rostral ventrolateral medulla. A large proportion of cells and processes of the rostral cell group were oriented medially and ventromedially. processes of C1 neurons were traced dorsally toward the nucleus tractus solitarii, dorsal motor nucleus, and principal tegmental adrenergic bundle, ventrally toward the ventral surface, laterally toward the trigeminal complex, and medially or ventromedially toward the raphe. C2 neurons were located in the dorsomedial medulla and were subdivided into four distinct populations: (1) neurons in the rostral nucleus paragigantocellularis pars dorsalis (NGCd) and medial longitudinal fasciculus (MLF) were contiguous and similar in size and shape, with their long diameters oriented horizontally or diagonally along several axes; (2) neurons of the periventricular gray were located in a cytoarchitecturally undefined area dorsal to the MLF; these cells were ovoid, smaller, and organized more compactly than those in the NGCd-MLF; (3) a cell group in the rostromedial nucleus tractus solitarii (NTS) and dorsal motor nucleus overflowed caudally into the intermediate thirds of both structures; and (4) a parvicellular group in the NTS was compactly organized in the dorsolateral NTS and was best developed at the level of the area postrema. Processes of C2 neurons were generally directed sagitally, medially, and laterally along the ventricular floor and ventrally or medially toward the raphe; other fibers arborized and terminated within the NTS and dorsal motor nucleus. In the medulla, local processes were traced from C1 and C2 neurons directly into respective ventral and dorsal parts of the medullary raphe and surrounding intraparenchymal blood vessels. Fibers from these neurons were also followed, respectively, onto the ventral subpial surface and the floor of the fourth ventricle.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical anatomy of the brain

The development of sensitive histochemical-neuroanatomical techniques has made it possible to analyze the content of specific compounds in single nerve cells and their processes. In consequence, it has been possible to construct detailed maps of the distribution of various types of neurons on the basis of their transmitter substance. There are now many examples of neurons containing both a classical transmitter and a peptide. In some instances the peptides seem to support the action of the classical transmitters. This interaction may have applications in the prevention and treatment of nervous disease states.