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Autoxidation pathways and redox reactions of dihydroxytryptamines (5,6- and 5,7-DHT) and of 6-hydroxydopamine (6-OH-DA) are illustrated, and their potential role in aminergic neurotoxicity is discussed. It is proposed that certain aspects of the cytotoxicity of 6-OH-DA and of the DHTs, namely redox cycling of their quinone- and quinoneimine-intermediates as a source of free radicals, may also apply to quinoidal reactive intermediates and to glutathionyl- or cysteinyl conjugates ("thioether adducts") of o-dihydroxylated (catechol-like) metabolites of certain substituted amphetamines (of methylenedioxymethamphetamine (MDMA) and of methylenedioxyamphetamine (MDA)). Despite similarities in their primary interaction with the plasmalemmal (serotonergic transporter/dopamine transporter, SERT/DAT) and vesicular monoamine transporters (VMAT2), MDMA and fenfluramine (N-ethyl-meta-trifluoromethamphetamine, Fen) differ substantially in many aspects of their metabolism, pharmacokinetics, pharmacology, and neurotoxicology profile; the consequences of these differences for neuronal response patterns and long-term survival prospects are not yet fully understood. However, sustained hyperthermia appears to be a critical factor in these differences. Methodological requirements for adequate detection and description of pre- and postsynaptic forms of drug-induced neurotoxicity are exemplified using recently published accounts. The inclusion of microglial markers into research strategies has widened contemporary pathogenetic concepts on methamphetamine (MA)-induced neurotoxicity as an example of inflammatory neurodegeneration, thus complementing the traditional ROS and RNS-dependent stress models. Amphetamine-type neurotoxicity studies may assist in elaborating of preventive strategies for human neurodegenerative disorders.

The present review deals with the anatomical distribution, physiological importance, and pathological implications of the neuronal-type nitric oxide synthase (nNOS) in skeletal muscle. Throughout the body, nNOS is located beneath the sarcolemma of skeletal muscle fibers. In rodents, nNOS is enriched in type IIb muscle fibers, but is more homogenously distributed among type II and type I fibers in humans and subhuman primates. It is accumulated on the postsynaptic membrane at the neuromuscular junction. An increased concentration of nNOS is noted at the sarcolemma of muscle spindle fibers, in particular nuclear bag fibers, which belong to type I fibers. The association of nNOS with the sarcolemma is mediated by the dystrophin-glycoprotein complex. Specifically, nNOS is linked to alpha 1-syntrophin through PDZ domain interactions. Possibly, it also directly binds to dystrophin. The activity and expression of nNOS are regulated by both myogenic and neurogenic factors. Besides acetylcholine, glutamate has also been shown to stimulate nNOS, probably acting through N-methyl-D-aspartate receptors, which are colocalized with nNOS at the junctional sarcolemma. Functional studies have implicated nitric oxide as a modulator of skeletal muscle contractility, mitochondrial respiration, carbohydrate metabolism, and neuromuscular transmission. A clinically relevant aspect of nNOS is its absence from the skeletal muscle sarcolemma of patients with Duchenne muscular dystrophy (DMD). A concept is presented which suggests that, as a consequence of the disruption of the dystrophin-glyoprotein complex in DMD, nNOS fails to become attached to the sarcolemma and is subject to downregulation in the cytosol.

Background: Serotonin may play a role in the pathophysiology of obsessive-compulsive disorder (OCD) because of the anti-obsessional effect of selective serotonin reuptake inhibitors (SSRIs)., Method: The literature is reviewed on knowledge of the role of serotonergic neurons in brain function, studies on monoamine metabolites in cerebrospinal fluid (CSF), various stress neuropeptides, neuroendocrine and behavioural challenge after administration of direct and indirect serotomimetic compounds, and neuroanatomical data on brain circuits organising behaviour., Results: In most of the OCD cases analysed, CSF 5-hydroxyindoleacetic acid and homovanillic acid concentrations do not significantly differ from age-corrected controls. However, a relationship appears to exist between pre-treatment levels of these metabolites and clinical response to drugs acting on the serotonin transporter. Abnormalities in CSF arginine vasopressin, corticotropin-releasing hormone, oxytocin and somatostatin levels have been reported in OCD. Long-term treatment with high-doses of clomipramine, fluvoxamine, and fluoxetine tend to correct these neuropeptide abnormalities., Conclusions: We hypothesise that continuous treatment with SSRIs alters serotonin turnover and neuropeptide expression patterns in OCD-entertaining functional forebrain/midbrain circuits.

The prenatal development of the serotonin transporter was analyzed in mouse brain and spinal cord by autoradiographic localization of [3H]citalopram binding. Transporter expression started at embryonic day (E) 12 in two discontinuous bands in the anterior and posterior brainstem. Labeling extended cranially and caudally, reaching the basal diencephalon at E 13, the septal complex at E 15, and the cerebral cortex at E 16. The caudal extension of the labeling descended at the ventrolateral margin of the spinal cord and reached lumbar levels at E 14. At E 17-E 18, [3H]citalopram binding emerged in the striatum, amygdaloid area, ventrobasal thalamus, paraventricular and periventricular hypothalamic nuclei, and substantia nigra. The overall spatiotemporal expression pattern of the serotonin transporter in the mouse agrees with data on the immunohistochemical localization of serotonin in the rat embryo. These results suggest that serotonergic fibers have the equipment to engage in transmitter reuptake long before synapse formation, and that transporter expression might represent a prerequesite for the developmental functions exerted by serotonin.

Neurones in the ureterovesical ganglion complex provide autonomic innervation to the pelvic ureter, the ureterovesical junction and the bladder trigone. We examined the distribution and peptide co-expression pattern of nitric oxide synthase (NOS) in the human ureterovesical ganglia by combining NADPH-diaphorase histochemistry with immunoreactivity for vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP). Less than 20% of nerve cells in the large ganglia of the ureterovesical complex were stained for NOS activity. In elderly individuals, ganglion cells regularly exhibited conspicuous morphological alterations suggestive of degenerative changes. Most of the NOS-positive cell bodies costained for VIP-immunoreactivity. A minority of NOS-expressing cells also reacted for NPY-immunoreactivity. CGRP-immunoreactivity was present in varicose terminal-like nerve fibres which were found to encircle NOS-containing perikarya. Occasionally, NOS-positive somata were surrounded by plexiform axon terminals which immunostained for VIP or NPY. We conclude that the passage of urine across the ureterovesical junction is under relaxatory control of a local nitric oxide/VIP(NPY) pathway which may be modulated by preganglionic efferent and/or primary afferent input.

Serotonin neurons in the rostral and caudal brainstem raphe nuclear groups give rise to collateralized ascending and descending projections which provide modulatory input into most networks throughout the entire neuraxis. The rostral raphe system is interconnected with target forebrain areas through reciprocal limbic-midbrain loops, which suggests that serotonin has a role in the regulation of complex intelligent adaptive behavior. Serotonergic pathways sensitize brainstem and spinal cord central rhythmic pattern generators which organize repetitive autonomic and motor activities, e.g. oral-buccal and nutritive behaviors, facilitate tonically active motor neurons innervating antigravity muscles, and disfacilitate somatosensory information processing. Serotonin effects are mediated by multiple receptor subtypes with distinct pre- and postsynaptic localization and regional distribution pattern. They belong to the G protein superfamily, coupling to adenylate cyclase (5-HT1,4,5,6,7) or phospholipase C (5-HT2), and to the ligand-gated ion channel superfamily (5-HT3). Drugs acting at these receptors are known to modulate various aspects of cooperative social behavior and responding latency, i.e. impulsivity, in a variety of experimental models of anxiety and depression. The clinical efficacy of the so-called selective serotonin reuptake inhibitors (SSRIs) in disorders characterized by poor impulse control, e.g. bulimia nervosa, obsessive-compulsive disorder (OCD) and violent suicidal or homicidal behavior, may likewise be due to improved responding latency.

The central projection systems represent an expansive and important component of the brainstem reticular core which provide modulatory input into multiple target networks throughout the entire vertebrate neuraxis. Most of the afferent input into the cranial raphe originates within sensory uni- and polymodal, associative and limbic cortices suggesting that serotonin modulates preprocessed information. The serotonergic neurons discharge in a remarkably stable and tonic fashion during wakefulness. Some 5-HT neurons increase their discharge rate phasically in association with the activation of central rhythmic pattern generators involved in consummatory and grooming behaviour. In concert with enhancing motor functions, the serotonergic systems discretely deamplify sensory attentiveness and pain processing, thereby establishing an essential and protective filter mechanism against distracting and irritating noise effects of sensory afferent input level. In addition, serotonin restrains the latency to responding, i.e. impulsivity. These effects of serotonin are mediated by multiple receptor subtypes with distinct pre- and postsynaptic localisation and regional distribution pattern, acting via amplifying (5-HT2 receptors) or desamplifying (5-HT1 receptors) G-protein-dependent transduction mechanisms. The breakdown of these protective and adaptive functions of 5-HT in complex behaviour and in basic aspects of sensorimotor integration may have a pathogenetic role in disorders of impulse control (e.g. bulimia nervosa and OCD) which have been found to respond to high-dose, long-term treatment with selective serotonin reuptake inhibitors.

In nerve tissue the histochemical nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reaction is considered a suitable marker for nitric oxide synthase (NOS) activity. We have previously shown that the NOS-specific inhibitor L-nitroarginine (L-NNA) can block NADPH-d staining in intermediolateral (IML) neurons of the rat spinal cord: such a reaction might serve as a control for the presence of a NOS-related catalytic activity, i.e., L-NNA-dependent NO synthesis in these neurons. However, L-NNA inhibition of neuronal NADPH-d is inconsistent and is therefore disputed by others. This prompted us to reinvestigate the reaction conditions to provide a standardized protocol for inhibition experiments. In IML neurons of formaldehyde-fixed spinal cord tissue, inhibition of NADPH-d reaction was tested by preincubation of frozen sections with the flavin-binder diphenylene iodonium chloride (DPI, 10 microM-1 mM) which blocked the NADPH-d reaction in a concentration-dependent way, suggesting an inverse relationship of inhibitor concentration and final reaction product generated. Preincubation with the NOS-specific inhibitor L-NNA in glycine-NaOH buffer (pH 8.5-9.5) but not L-nitroarginine methyl ester (L-NAME) revealed a concentration-dependent blocking effect on neuronal NADPH-d comparable to the effects seen with DPI, suggesting the existence of a L-NNA sensitive NADPH-d activity. Blocking with L-NNA (100 microM-10 mM) was prevented by excess L-arginine (10-100 mM), suggesting competitive binding sites. NADPH-d staining was not inhibited by 7-nitro indazole, another NOS inhibitor. Thus, in formaldehyde-fixed nervous tissue both DPI and L-NNA inhibit the NOS-associated catalytic NADPH-d activity, thereby preventing NADPH-dependent conversion of nitroblue tetrazolium to formazan.

We investigated the distribution pattern of nitric oxide (NO) synthesizing nerve cell bodies and axons in the biliary system of the guinea-pig using immunohistochemistry for nitric oxide synthase (NOS). Nerve fibres staining for NOS were found to contact non-vascular smooth myocytes and to course beneath the epithelium. No perivascular NOS fibres were observed. The innervation density varied in different parts of the biliary tree. The lower portion of the common bile duct was more richly innervated than the remaining parts of the duct system. NOS-containing neurones encompassed a subpopulation of intramural ganglion cells. Sympathetic neurones in the coeliac ganglion were not stained. It is suggested that intrinsic NOergic neurones are involved in inhibitory motor control of the biliary musculature, including the sphincter of Oddi.

Nitric oxide (NO) is generated intracellularly from L-arginine by the action of the enzyme nitric oxide synthase (NOS). The present investigation demonstrates immunoreactivity against NOS and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity in nerve cells and fibers of the reproductive system of the female mouse. The density of nerve fibers staining for NOS varied among different genital organs. The ovary and Fallopian tube were devoid of NOS-positive nerves. The uterine horns received sparse innervation by NOS-containing nerve fibers. The most abundant NOergic innervation was found in the uterine cervix and vagina, where the nerve fibers ran parallel to the smooth muscle bundles and beneath the epithelium; they also accompanied intramural blood vessels. The vaginal muscular wall contained single or groups of NOS-reactive nerve cells. Clusters of NOS-containing neurons were located in Frankenhäuser's ganglion at the cervico-vaginal junction. NO may therefore act as a transmitter in the nervous control of the female reproductive tract.

Considerable evidence suggests that nitric oxide (NO) acts as a nonadrenergic noncholinergic (NANC) transmitter at autonomic neuroeffector junctions. NO is generated enzymatically from L-arginine by a constitutive, cytosolic, Ca2+/calmodulin-activated NO synthase (NOS): NADPH- and tetrahydrobiopterin-dependent cytochrome P-450-type hemoprotein. Electrophysiological and pharmacological data indicate that NO fulfils most of the criteria for a neurotransmitter. It is released from axon terminals when invaded by action potentials and mimics the effect of nerve stimulation. The changes in the mechanical and/or electrical activity of smooth muscle preparations in response to transmural stimulation of NANC nerves are antagonized by inhibitors of NO synthesis or oxyhemoglobin, an NO scavenger. NO acts principally by stimulating soluble guanylate cyclase. Studies on the histochemical localization of NOS point to the involvement of the neural L-arginine-NO pathway in the regulation of vascular tone and of several aspects of respiratory, gastrointestinal, and genitourinary tract functions.

Neural regeneration is a multistep event which appears to be controlled by neurotrophic factors such as neurotrophins and/or neurotrophic cytokines. Following traumatic, age- and/or disease-related responses, these molecules may be expressed and/or released by innervated target cells, neuron-ensheathing glial cells, recruited macrophages or by the neural somata themselves which altogether provide possible cues for neurotrophic strategies in vivo. In this respect, neurotrophic molecules may follow either paracrine, autocrine or even intracrine pathways in order to attenuate or even prevent neuronal degeneration. As neurotrophic molecules may have important functions as putative therapeutic agents for patients suffering from CNS disorders or from peripheral neuropathies, adequate and reliable animal lesion paradigms are of importance as in vivo assay systems. Axotomy models or selective neurotoxin-lesion models of anatomically well-defined neuron target connections are a first step towards assaying of neurotrophic actions in vivo. In lesioned central neural pathways, the existence of multineuronal networks, diffuse nuclear topography and a high degree of collateralization should be considered when studying regenerative potentials of trophic factors. Because of their simple organization and accessibility, peripheral neural pathways are particularly appealing as assay systems. As neurotrophic requirements and vulnerability vary among neural subsystems, in vivo lesion paradigms reveal pharmacological rather than physiological effects which have to be elucidated by more sophisticated experimental paradigms and molecular tools.

We have used a polyclonal monospecific antibody to rat cerebellum nitric oxide synthase type I (NOS-I, 160 kD) in combination with reduced NADPH-diaphorase histochemical reaction (NADPH-d) to verify colocalization of both NOS protein and NOS enzymatic activity in the rat spinal cord autonomic system. Strong immunoreactivity (IR) of NOS-I was clearly detected in the four main thoracolumbar autonomic nuclei in spinal cord layers of Rexed's laminae VI, VII and X. In all labelled neurones, NOS-I-IR colocalized with NADPH-d activity, suggesting coexistence of brain-specific NOS-I-like protein and its associated enzyme activity. For these neurones the new term 'nitroxergic' (i.e. NO-generating) neurones appears to be justified. Spinal cord nitroxergic neurones are part of a NO-mediated signal transduction pathway for control of the sympathetic 'outflow' to various peripheral target organs.

We have used retrograde fluorescent tracing (fast blue) both before (prelabeling) and at time points after selective unilateral adrenomedullectomy in vivo (post-labeling) in order to investigate the survival and morphology of sympathoadrenal preganglionic (SAP) neurons located in the lower thoracic intermediolateral (IML) cell column of the adult rat spinal cord. By prelabeling with fast blue it was found that the majority (i.e., more than 85%) of the SAP neurons underwent degeneration and were lost from the IML cell column within 4 weeks after peripheral target lesion and administration of intramedullary gelfoam implants containing a nontrophic control protein cytochrome c. By contrast, atrophy and loss of SAP neurons was largely prevented by local treatment (intramedullary implants) with recombinant basic fibroblast growth factor (bFGF) as determined from counts of large and "healthy-looking" prelabeled neurons within the IML column ipsilateral to the lesioned (i.e., operated) side 4 weeks postimplantation. The time course of withdrawal of preganglionic axons from their lesioned target area was investigated by fast blue injections into intramedullary (control or bFGF) implants at weekly intervals postimplantation (postlabeling) and was documented by counting the number of healthy SAP neurons that retained the label. Without bFGF treatment, progressive numerical loss of SAP neurons was evident within 1 to 4 weeks postlesioning, indicative of pronounced retrograde cell degeneration. Retrograde cell degeneration was insignificant during the first 2 weeks postimplantation after early postlesion treatment with exogenous bFGF; it was apparently postponed to occur after 1 month. Implantation of gelfoam containing neutralizing anti-bFGF-antibodies resulted in accelerated retrograde axon degeneration implying that bFGF is an endogenous trophic factor for SAP neurons. The results are consistent with the idea that SAP neurons actually die following peripheral target lesion and are not supported from other trophic sources. However, these neurons can be prevented from disconnection-induced death by providing exogenous bFGF. Limited amounts of endogenous FGF may also become available to SAP axons by disintegration of nerve terminal-surrounding cells delaying the process of retrograde SAP neuron death.

We have used nitric oxide synthase (NOS) histochemistry as a perikaryal viability marker to trace the retrograde reaction of spinal cord intermediolateral (IML) sympathoadrenal projection (SAP)-neurons to target-removal, i.e., selective adrenomedullectomy and local administration of either insulin-like growth factor-I (IGF-I), basic fibroblast growth factor (bFGF) or a combination of both. Counting of NOS-positive preganglionic spinal cord neurons 4 weeks post surgery indicated that more than 80% of stained neurons were lost from the IML-cell column. This percentage loss corresponds to the numerical loss of NOS-stained SAP-neurons labeled retrogradely with Fast-blue prior to adrenomedullectomy. Basic FGF-supplementation at the site of lesion resulted in maintenance of the majority of NOS-positive IML-neurons, a finding confirmed by the survival rate of Fast-blue prelabeled SAP-neurons. Thus, besides maintenance of the structural integrity of SAP-neurons, bFGF prevents loss of intracellular NOS-activity which may reflect unaltered cell metabolism (and function) of these neurons following target-removal in vivo. By contrast, IGF-I failed to alter the rate of disappearance of NOS-staining and labeling index of neurons within the IML-cell column postlesion, suggesting that IGF-I is not neurotrophic for SAP-neurons by itself. Combined treatment with both factors resulted in a more widespread loss of NOS-stained and Fast-blue-prelabeled SAP-neurons than registered after bFGF-only treatment. No co-trophic effect of bFGF and IGF-I was evident; rather, the pronounced bFGF-induced rescuing effect was significantly suppressed by exogenous IGF-I in vivo, supporting the idea that this or another molecule induced by the treatment enhances rather than prevents retrograde degeneration and neuronal death within the adult lesioned IML-adrenal pathway.

Nitric oxide synthetase (NOS) can be selectively stained in neurons by either NADPH-diaphorase (i.e., NOS)-histochemistry or immunohistochemistry with antibodies raised against NOS, which apparently label identical reactive sites (Hope, B.T., G.J. Michael, K.M. Knigge, and S.R. Vincent, Proc. Natl. Acad. Sci. USA 88:2811-2814, '91). We provide histochemical evidence for the existence of a neuron-specific NOS-activity in autonomic neurons of the thoracic spinal cord. Among the four main preganglionic cell clusters investigated at mid-thoracic levels, Th7-10, the intermediolateral (IML)-cell column was the most prominently stained cell group. The histochemical staining was absent in other spinal cord neurons and non-neuronal cells, e.g., GFAP-positive glial cells. Staining was completely blocked by N omega-nitro-L-arginine (L-NNA), a potent NOS-inhibitor for brain and peripheral autonomic neurons, but was still observed in the presence of another NOS-inhibitor, N omega-monomethyl-L-arginine (MeArg). The NOS-activity co-localized with nearly half of the ChAT-immunostained neurons located in the mid-thoracic IML-cell column as quantified by cell counts in single and double-stained tissue sections. We conclude that NOS-activity-containing neurons represent a distinct group among cholinergic IML-neurons, which suggests a more general function of this newly defined subpopulation of the spinal cord autonomic system. In vivo Fast blue retrograde labeling combined with histochemical staining and immunostaining revealed that sympathoadrenal projection neurons belong to the distinct NOS and ChAT-positive IML-cell group.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to identify possible sites of synthesis of nitric oxide in the peripheral nervous system, several mouse organs were investigated for the presence of NADPH-diaphorase activity. Diaphorase-positive neurons and fibers were localized in the tongue, submandibular salivary glands, gastrointestinal and biliary duct systems, lower urinary tract and pelvic ganglia. By thionin counterstaining it was found that a distinct subpopulation of neurons was labeled. The present study indicates that nitric oxide synthase may be present in intrinsic neurons of various organs, suggesting a widespread function of nitric oxide in the peripheral autonomic nervous system.

[3H]Flunitrazepam binding sites were analysed in the cerebellar cortex, deep cerebellar and vestibular nuclei of Purkinje cell deficit (pcd) mutant mice which have an almost complete postnatal loss of Purkinje cells, and weaver mutant mice, in which there is a postnatal degeneration of granule cells. Increases in [3H]flunitrazepam binding site densities were found in the molecular and granule cell layer of weaver mutant mice, whereas decreases were observed in pcd mutant mice when compared to wildtype 'control' mice. Apparently unaltered benzodiazepine receptor densities were found in the flocculus of pcd mutant mice, whereas increases were seen in the flocculus of weaver mutant mice. The densities of benzodiazepine binding sites in the medial and lateral deep cerebellar nuclei of both mutants significantly exceeded those in control mice. Significant increases in flunitrazepam binding sites were also found in the superior and spinal nucleus of the vestibular complex of pcd mice as compared to wildtype. In the weaver mutants the benzodiazepine receptor density is enhanced in the superior and medial vestibular nucleus. Apparently unaltered numbers of such receptors compared to the wildtype control group were found in the remaining vestibular nuclei of both mutants.

The development of inhibitory receptors in rat spinal cord was investigated by autoradiography using [3H]flunitrazepam as a ligand for benzodiazepine receptors and [3H]strychnine as a ligand for glycine receptors. The development of benzodiazepine receptors follows a similar pattern at all levels of the spinal cord. The density of [3H]flunitrazepam binding sites is already high at birth, increases 2-fold by days 3-7 and thereafter declines to levels already present at birth. In contrast, [3H]strychnine binding sites are weakly expressed at birth and increase up to 7-fold between days 4 and 21. A craniocaudal gradient in the development of glycine receptors is not apparent. However, maturation of [3H]strychnine binding in the ventral horn precedes that in the dorsal horn for 3-4 days. In summary, the developmental expression of these two inhibitory receptors in the spinal cord appears to be regulated differently.

The anatomical distribution of [3H]norharman binding sites was determined by quantitative autoradiography in rat brain slices. They are enriched in hypothalamic, thalamic, accumbens and amygdaloid nuclei as well as in hippocampal, neocortical and olfactory-related structures. The distribution pattern differs from that of other previously described receptors or binding sites (e.g. monoamine oxidase, benzodiazepine, tryptamine, 5-hydroxytryptamine receptors (5-HT1A, 5-HT1B, 5-HT1C, 5HT2], which suggests that a unique class of [3H]norharman binding sites exists in the rat brain. The findings are consistent with previous experiments which showed high affinity binding sites for [3H]norharman in rat brain membranes (KD 1.552 nM; autoradiography KD 5.5 nM). A correspondence in the displacing activity of drugs was found for both methods (crude membrane fraction: harman much greater than tryptamine much greater than 5-hydroxytryptamine greater than N-methyl-beta-carboline-3-carboxamide (FG 7142) = diazepam; autoradiography: harman much greater than tryptamine much greater than FG 7142 greater than 5-hydroxytryptamine greater than diazepam). Provided that the binding sites represent functional receptors, the present anatomical findings may explain the biological effects of norharman, e. g. pro-conflict behaviour (limbic-hypothalamic structures), tonic-clonic convulsions (limbic-cortical structures) and alterations of locomotor activity (accumbens nucleus).

(3H)Buspirone binds with high affinity (KD = 11 nM) to sections from rat striatum. Spiroperidol, chlorpromazine, (+)-butaclamol and apomorphine are the most potent inhibitors of (3H)buspirone binding. Ketanserin, SCH 23390, serotonin and phentolamine are clearly less active. The regional distribution of (3H)buspirone binding in rat and marmoset brain is characterized by high silver grain densities in the olfactory tubercle, nucleus accumbens and striatum. In the hypophysis, the pars intermedia is strongly labeled. Within the hippocampal formation, slightly higher binding site densities are found in the dentate gyrus. The distribution pattern of binding sites in the dentate gyrus varies according to the species investigated. The data presented in this study permit the conclusion that (3H)buspirone binds with high affinity to dopamine 2 receptors but do not exclude additional binding to other types of receptors, e.g. 5-HT1 receptors. The interaction of buspirone with dopamine 2 receptors may be mainly responsible for its pharmacological profile.

The present report describes the distribution of tritium label after injection of newborn rats with [3H]6-hydroxydopamine ([3H]6-OHDA). The animals were injected either intracisternally (i.c.) or subcutaneously (s.c.), with or without pretreatment with nomifensine, which blocks the high-affinity uptake of both noradrenaline (NA) and dopamine (DA), and sacrificed at intervals from 40 min to 24 h post-injection (p.i.). In i.c. injected animals, tritium label is demonstrable as early as 40 min p.i. in neurons of all known NA and DA cell groups. In NA neurons, it is taken up into cell body, dendrites, preterminal and terminal axons. The intensity of neuronal labeling is highest within the first 4 h p.i. and decreases in most neurons with longer postinjection intervals. A significant proportion of both NA and DA neurons degenerate beginning 6 h p.i., the majority show morphological signs of the axon reaction 24 h p.i. Uptake of [3H]6-OHDA into serotonergic and non-catecholaminergic neurons is not demonstrable. [3H]6-OHDA is accumulated by the following extraneuronal cells of the CNS: ependymal cells, epithelial cells of the choroid plexus, subependymal macrophages, smooth muscle cells in the wall of large intraparenchymal blood vessels, meningeal cells and glial cells. The time course of accumulation and disappearance of the label varies among these extraneuronal elements. The meningeal cells show the highest labeling intensity and degenerate within 24 h p.i. After pretreatment of the animals with nomifensine, the uptake of [3H]6-OHDA into NA and DA neurons is totally blocked; by contrast uptake of the labeled drug into extraneuronal cells is not prevented. These findings show that [3H]6-OHDA is not only accumulated by neurons possessing the high-affinity uptake for NA or DA, but by numerous other, extraneuronal cells which also participate in the metabolism of catecholamines.

Rolipram is a clinically effective antidepressant with selective cAMP phosphodiesterase (PDE) inhibiting properties. (+/-)-[3H]Rolipram binds with high affinity (Kd = 2.52 +/- 0.47 nM) to sections of rat brain (Hill number = 0.90 +/- 0.05). Binding is stereospecific. Association of (+/-) [3H]rolipram to sections is rapid (47% of specific binding in the first minute, kobs = 0.52 min-1). Dissociation of (+/-)-[3H]rolipram exhibits non first order kinetics (3 component model; t1/2 = 2.5 min, 50 min and 6 h, respectively). A number of PDE inhibitors reduce (+/-)-[3H]rolipram binding to the level of nonspecific binding ((-)-rolipram, IC50 = 0.9 nM; (+/-)-rolipram, IC50 = 1.5 nM; Ro 20-1724, IC50 = 11 nM; ICI 63.197, IC50 = 35 nM; medazepam, IC50 = 240 nM; diazepam, IC50 = 1200 nM; IBMX, IC50 = 3800 nM). In vitro autoradiography reveals high binding site densities in the cerebellum, olfactory bulb, lateral septal nucleus, frontal cortex, subiculum and CA1 of hippocampus. Most of the labeled structures are part of the limbic system. In vivo autoradiography of (+/-)-[3H]rolipram binding shows much more nonspecific binding than in vitro, nevertheless the distribution pattern of (+/-)-[3H]rolipram binding sites is similar. A comparison of the distribution pattern of (+/-)-[3H]rolipram binding sites with that of an antidepressant (monoamine oxidase inhibitor, monoamine uptake inhibitor) reveals no overlap. Limited, though significant correlations exist with the distribution of beta 1-adrenergic, adenosine1 and glutamate/quisqualate receptors as well as protein kinase C, but not with beta 2-adrenergic receptors and forskolin binding sites.

Time-dependent changes in regional CNS noradrenaline (NA) concentration, 3H-NA uptake and fluorescence morphology of CNS NA neurons were analysed in the adult rat up to 6 months after intraventricular injection of 5,7-dihydroxytryptamine (5,7-DHT), and compared with the time-course of changes in brain and spinal cord indolamine neurons. Following a substantial depletion of both amines in all CNS regions (telodiencephalon, brainstem and spinal cord) at 10 days after 150 mug 5,7-DHT, brain NA--but not 5-HT--levels recovered to near-normal values in brainstem and forebrain (35% below the age-matched controls) within 4 months. This was accompanied by a total restoration of the initially decreased capacity of the brain tissue to accumulate 3H-NA in vitro. Within 10 days after 5,7-DHT, there was a disappearance of NA terminals from many telencephalic, diencephalic and lower brain stem nuclei, from the cerebral and cerebellar cortices, and the grey matter of the spinal cord, concomitant with the appearance of numerous distorted, highly fluorescent swellings along the non-terminal axons of the major noradrenergic projection pathways. The recovery of the NA levels was paralleled by a re-appearance of fluorescent fibres, signifying an intense sprouting and regrowth of the drug-lesioned axons, which eventually re-innervated some of the previously denervated telodiencephalic regions. Except for a permanent loss of some surface-near perikarya in group A1 (the main source of the bulbospinal projections) there was no evidence of a retrograde degeneration of noradrenergic cell bodies in the rat CNS. The results are compatible with the idea that 5,7-DHT mainly causes a lesion of NA axons at a distance from the cell bodies, and this is followed by sprouting and regrowth of axons from the lisioned neurites, and formation of new terminal-like fibres in some previously denervated telodiencephalic regions. These findings indicate that chemical axotomy of central NA neurons induced by 5,7-DHT is--in contrast to that induced by 6-hydroxydopamine--followed by extensive axonal regeneration.

Binding sites for [3H]buspirone were identified on sections from rat brain by light microscopic autoradiography. Incubated sections were processed by the Ultrofilm as well as the coverslip method. Highest densities of [3H]buspirone binding were localized in the caudate/putamen, nucleus accumbens septi, olfactory tubercle and in the glomerula of the olfactory bulb. This distribution pattern is different from any serotonin receptor but fits well with that of dopamine receptors. Therefore, this study supports the hypothesis that buspirone acts, at least partially, on dopamine receptors.

The neurotoxins 5,6- and 5,7-dihydroxytryptamine are accepted tools for "chemical degeneration" of serotonergic (5-HT) axons in the CNS (for reviews, see [11, 12, 15, 20] ). Optimum application of these substances requires knowledge of their chemical properties, disposition in the biophase and mechanism of action. Current knowledge and concepts on this issue are described and results of recent studies utilizing 5,7-DHT uptake as a tool for localizing 5-HT neurons neuroanatomically are reviewed.

The sympathetic innervation of the liver of monkey and man has been investigated in a combined fluorescence histochemical, chemical and electron microscopical study. By means of the Falck-Hillarp fluorescence method a dense network of monoamine-containing nerve fibers was visualized in liver tissue of monkey and man. The nerve fibers ran in close contact to both hepatocytes and blood vessels. Chemical quantitations showed high concentrations of noradrenaline in both human and monkey liver. Microspectrofluorometry of the intraneuronal monoamine resulted in spectra characteristic of a catecholamine. For the electron microscopical study the dopamine analogue, 5-hydroxydopamine, was used to "label" the catecholamine terminals in both human and monkey liver. The nerve profiles, identified as catecholamine-containing, were demonstrated in a perivascular location and in close contact to hepatocytes. No synaptic membrane specializations were present between nerve fibers and hepatocytes. The general ultramorphology and intralobular distribution pattern of nerves in the liver of monkey and man were similar. The present results prove the existence of a sympathetic innervation of hepatocytes and blood vessels in the liver of man and monkey.

In the isolated, perfused kidney of untreated and catcholamine-depleted rats (by 6-hydroxydopamine and reserpine), dopamine (DA) caused a dose-dependent increase in vascular resistance which could be prevented by prior blockade of the alpha-adreno-receptors. The DA-induced vasoconstriction thus appears to be due to a direct stimulation of alpha-receptors in the kidney rather than an indirect sympathomimetic effect through release of noradrena-line from local adrenergic nerve terminals. The effectiveness of the chemical sympathectomy accomplished with 6-hydroxydopamine and reserpine was evaluated by chemical; histochemical and electron microscopical methods.

1. Slow infusion of 5,7-DHT into the left lateral ventricle of nomifensine pretreated, pentobarbitone anaesthetized rats produces moderate, asymmetric regional forebrain 5-HT depletions 24 h after the injection; rapid pulse injection of 5,7-DHT results in more extensive and almost symmetric 5-HT reductions. By the eighth day, both injection procedures cause a comparable pattern of 5-HT depletion throughout the CNS. RAdioactivity distribution patterns (following 14C-5,7-DHT) correlate with the characteristics of 5-HT depletions. The type of anaesthetic used (pentobarbitone; pentobarbitone plus ketamine; ether) has little, if any, influence on the long-term 5-HT reductions in the rat CNS. 2. In forebrain regions, near the ventricle, nomifensine does not totally protect catecholamine fibre systems when pentobarbitone is used as the anaesthetic. However, optimum selectivity is provided by a combination of DMI and nomifensine in animals anaesthetized with a combination of pentobarbitone and ketamine. 3. Reaction of 5,6- and 5,7-DHT with oxygen is essential for these drugs to act as neurotoxins. Both drugs interact with the electron transfer chain of mitochondria (at the site of complex III) resulting in accelerated formation of reactive quinoidal intermediates. Metabolism of 5,7-DHT by MAO contributes to the overall in vivo neurotoxicity of this m-substituted dihydroxytryptamine.