Distribution of dopamine-containing neurons and fibres in the feline medulla oblongata: a comparative study using catecholamine-synthesizing enzyme and dopamine immunohistochemistry

TRPV1-Like Immunoreactivity in the Human Locus K, a Distinct Subregion of the Cuneate Nucleus

The presence of transient receptor potential vanilloid type-1 receptor (TRPV1)-like immunoreactivity (LI), in the form of nerve fibres and terminals, is shown in a set of discrete gray matter subregions placed in the territory of the human cuneate nucleus. We showed previously that those subregions share neurochemical and structural features with the protopathic nuclei and, after the ancient name of our town, collectively call them Locus Karalis, and briefly Locus K. TRPV1-LI in the Locus K is codistributed, though not perfectly overlapped, with that of the neuropeptides calcitonin gene-related peptide and substance P, the topography of the elements immunoreactive to the three markers, in relation to each other, reflecting that previously described in the caudal spinal trigeminal nucleus. Myelin stainings show that myelinated fibres, abundant in the cuneate, gracile and trigeminal magnocellular nuclei, are scarce in the Locus K as in the trigeminal substantia gelatinosa. Morphometric analysis shows that cell size and density of Locus K neurons are consistent with those of the trigeminal substantia gelatinosa and significantly different from those of the magnocellular trigeminal, solitary and dorsal column nuclei. We propose that Locus K is a special component of the human dorsal column nuclei. Its functional role remains to be determined, but TRPV1 appears to play a part in it.

Sexually-dimorphic expression of tyrosine hydroxylase immunoreactivity in the brain of a vocal teleost fish (Porichthys notatus)

Vocal communication has emerged as a powerful model for the study of neural mechanisms of social behavior. Modulatory neurochemicals postulated to play a central role in social behavior, related to motivation, arousal, incentive and reward, include the catecholamines, particularly dopamine and noradrenaline. Many questions remain regarding the functional mechanisms by which these modulators interact with sensory and motor systems. Here, we begin to address these questions in a model system for vocal and social behavior, the plainfin midshipman fish (Porichthys notatus). We mapped the distribution of immunoreactivity for the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in the midshipman brain. The general pattern of TH(+) cell groups in midshipman appears to be highly conserved with other teleost fish, with a few exceptions, including the apparent absence of pretectal catecholamine cells. Many components of the midshipman vocal and auditory systems were innervated by TH(+) fibers and terminals, including portions of the subpallial area ventralis, the preoptic complex, and the anterior hypothalamus, the midbrain periaqueductal gray and torus semicircularis, several hindbrain auditory nuclei, and parts of the hindbrain vocal pattern generator. These areas thus represent potential sites for catecholamine modulation of vocal and/or auditory behavior. To begin to test functionally whether catecholamines modulate vocal social behaviors, we hypothesized that male and female midshipman, which are sexually dimorphic in both their vocal-motor repertoires and in their responses to hearing conspecific vocalizations, should exhibit sexually dimorphic expression of TH immunoreactivity in their vocal and/or auditory systems. We used quantitative immunohistochemical techniques to test this hypothesis across a number of brain areas. We found significantly higher levels of TH expression in male midshipman relative to females in the TH cell population in the paraventricular organ of the diencephalon and in the TH-innervated torus semicircularis, the main teleost midbrain auditory structure. The torus semicircularis has been implicated in sexually dimorphic behavioral responses to conspecific vocalizations. Our data thus support the general idea that catecholamines modulate vocal and auditory processing in midshipman, and the specific hypothesis that they shape sexually dimorphic auditory responses in the auditory midbrain.

The human cuneate nucleus contains discrete subregions whose neurochemical features match those of the relay nuclei for nociceptive information

The present paper is aimed at defining distinctive subdivisions of the human cuneate nucleus (Cu), evident from prenatal to old life, whose occurrence has never been clearly formalized in the human brain, or described in other species so far. It extends our early observations on the presence of gray matter areas that host strong substance P (SP) immunoreactivity in the territory of the human Cu and adjacent cuneate fascicle. Here we provide a three-dimensional reconstruction of the Cu fields rich in SP and further identify those areas by means of their immunoreactivity to the neuropeptides SP, calcitonin gene-related peptide, methionine- and leucine-enkephalin, peptide histidine-isoleucine, somatostatin and galanin, to the trophins glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor, and to the neuroplasticity proteins polysialylated neural cell adhesion molecule and growth-associated protein-43. The presence, density and distribution of immunoreactivity for each of these molecules closely resemble those occurring in the superficial layers of the caudal spinal trigeminal nucleus (Sp5C). Myelin and Nissl stainings suggest that those Cu subregions and the Sp5C superficial layers share a similar histological aspect. This work establishes the existence of definite subregions, localized within the Cu territory, that bear the neurochemical and histological features of sensory nuclei committed to the neurotransmission of protopathic stimuli, including pain. These findings appear of particular interest when considering that functional, preclinical and clinical studies show that the dorsal column nuclei, classical relay station of fine somatic tactile and proprioceptive sensory stimuli, are also involved in pain neurotransmission.

Activation of D2-like dopamine receptors inhibits GABA and glycinergic neurotransmission to pre-motor cardiac vagal neurons in the nucleus ambiguus

The parasympathetic control of heart rate arises from premotor cardiac vagal neurons (CVNs) located in the nucleus ambiguus (NA). Previous microinjection studies in NA show that dopamine evokes a decrease in heart rate, but the underlying mechanisms responsible for these responses were not identified. This study tested whether dopamine modulates inhibitory GABAergic and glycinergic and/or excitatory glutamatergic neurotransmission to CVNs. Retrogradely labeled CVNs were identified in an in vitro rat brainstem slice preparation and synaptic events were recorded using whole cell voltage clamp techniques. Bath application of dopamine (100 μM) had no effect on excitatory synaptic events, but reversibly inhibited the frequency (but not amplitude) of GABAergic inhibitory postsynaptic currents (IPSCs) in CVNs. Similarly, dopamine (10 μM and 100 μM) inhibited glycinergic IPSC frequency by ~50% and 70% respectively. The reduction in inhibitory neurotransmission to CVNs by dopamine was prevented by the sodium channel blocker TTX (1μM) indicating that the dopamine mediated effects were action potential dependent. Dopamine evoked responses were mimicked by the D2-like receptor agonist, Quinpirole but not D1-like receptor agonist, SKF 38393. In addition, the dopamine mediated depression of inhibitory synaptic responses were prevented by the D2-like receptor antagonist sulpiride, but not by D1-like or adrenergic or serotonergic receptor antagonists, suggesting that these responses were D2-like receptor mediated and not D1-like or adrenergic or 5-HT receptor mediated. These data suggest that dopamine acts via dis-inhibition, and diminishes inhibitory GABAergic and glycinergic neurotransmission to CVNs, which would be predicted to increase parasympathetic activity to the heart and evoke a bradycardia.

Gastroparesis and Parkinson's disease: a systematic review

Some of the gastrointestinal (GI) symptoms commonly experienced by patients with Parkinson's disease (PD) have been attributed to gastroparesis; however, the precise prevalence and relevance of gastric emptying delay in PD is unclear. The definition of gastroparesis varies; currently the most widely accepted definition (from the National Institute of Diabetes and Digestive and Kidney Diseases Gastroparesis Clinical Research Consortium) is the presence of appropriate symptoms (including nausea, retching, vomiting, stomach fullness, and inability to finish a meal) for ≥ 12 weeks, together with delayed gastric emptying on scintigraphy and the absence of any obstructive lesions on upper GI endoscopy. In PD patients, gastroparesis has the potential to affect nutrition and quality of life, as well as the absorption of PD medications, including L-dopa. This reduced absorption of L-dopa has implications for the control of the PD motor symptoms for which it is administered. We performed a systematic review of the literature on gastroparesis in PD with the aim of developing an evidence-based approach to its management. Based on this review, we conclude that while gastric emptying has been reported to be frequently delayed in PD, the existing data do not permit definitive conclusions concerning its true prevalence, relationship to the underlying disease process, relevance to PD management, or the optimal therapy of related GI symptoms. Further study of these important issues is, therefore, required.

In vitro examination of degenerative evolution of adrenergic nerve endings in pulmonary inflammatory [corrected] processes in newborns

Morphological aspect of tracheal preparations and pulmonary tissue was studied in vitro. The material was obtained from autopsy of newborns that died from different causes. Examinations were made in different gestational periods (immature 23-29 weeks; premature 30-37 weeks; mature >38 weeks). Material for examination was obtained up to 6 hours after death. Pulmonary and tracheal tissue was incubated for fixation in buffered formalin (10%). Special histochemical and histoenzymatic methods were used for coloring of pulmonary and tracheal tissue and the activity of ATP-ase and dopaoxidase was monitored. Cut out models were made in series of 7 micro, 10 micro and 20 micro. In peripheral axons of tracheobronchial pathways, degenerative alterations of adrenergic nerve endings in lung inflammatory processes were documented. These morphologic neuronal changes were described: Walerians degeneration, neuro-axonal degeneration and segment demyelinisation. These changes are well seen with argentafine coloring (Sevier-Munger modification for nerve endings) and with dopaoxidase reaction. In mature newborns that died from respiratory distress syndrome, we found different forms of metabolic and toxic degenerative damage in peripheral axons, such as: segment demyelinisation, neurotubular fragmentation, Schwann cell proliferation, fragmentation and bulging out of axonal neurotubules and neurofilaments. In tracheo-bronchial tissue, chromafine granules are homogeneously distributed on Lamina propria layer and through glandular structures. This gives as a contradiction, according to some authors, that adrenergic nerve fibers for muscle tissue are absent and that adrenaline and noradrenaline diffuse in muscle tissue from interstice.

Localization of L-DOPA uptake and decarboxylating neuronal structures in the cat brain using dopamine immunohistochemistry

The present study examined dopamine-immunoreactive neuronal structures using immunohistochemistry in conjunction with an anti-dopamine antiserum, following injection of l-3,4-dihydroxyphenylalanine (L-DOPA) with or without an inhibitor of monoamine oxidase (Pargyline) in the cat brain. L-DOPA injection made it possible to detect dopamine immunoreactivity in presumptive serotonergic and noradrenergic cell bodies and axons. Weak to moderate dopamine immunoreactivity was observed in non-aminergic cells (possibly so-called "D" cells containing aromatic L-amino acid decarboxylase (AADC)) in several hypothalamic, midbrain, pontine and medullary nuclei. Intense dopamine immunoreactivity became visible in a large number of cells and axons (possibly containing AADC) with wide distribution in the brain following administration of L-DOPA with Pargyline. AADC is most likely active in cells and axons that take up L-DOPA, where it decarboxylates the L-DOPA to dopamine. However, newly synthesized dopamine in such cells is rapidly oxidized by monoamine oxidase.

Swallowing abnormalities and dyskinesia in Parkinson's disease

Gastrointestinal abnormalities in Parkinson's disease (PD) have been known for almost two centuries, but many aspects concerning their pathophysiology have not been completely clarified. The aim of this study was to characterize the oropharyngeal dynamics in PD patients with and without levodopa-induced dyskinesia. Fifteen dyskinetic, 12 nondyskinetic patients, and a control group were included. Patients were asked about dysphagia and evaluated with the Unified Parkinson's Disease Rating Scale Parts II and III and the Hoehn and Yahr scale. Deglutition was assessed using modified barium swallow with videofluoroscopy. Nondyskinetic patients, but not the dyskinetic ones, showed less oropharyngeal swallowing efficiency (OPSE) for liquid food than controls (Dunnett, P = 0.02). Dyskinetic patients tended to have a greater OPSE than nondyskinetic (Dunnett, P = 0.06). Patients who were using a higher dose of levodopa had a greater OPSE and a trend toward a smaller oral transit time (Pearson's correlation, P = 0.01 and 0.08, respectively). Neither the report of dysphagia nor any of the PD severity parameters correlated to the videofluoroscopic variables. In the current study, dyskinetic patients performed better in swallowing function, which could be explained on the basis of a greater levodopa dose. Our results suggest a role for levodopa in the oral phase of deglutition and confirm that dysphagia is not a good predictor of deglutition alterations in PD.

Role of the lateral parabrachial nucleus in apomorphine-induced conditioned consumption reduction: cooling lesions and relationship of c-Fos-like immunoreactivity to strength of conditioning

The following experiments were designed to determine whether the lateral parabrachial nucleus (lPBN) mediates acquisition of conditioned consumption reduction induced by apomorphine, an agent that also has reinforcing properties. Temporary cooling lesions of the PBN blocked acquisition of apomorphine-induced conditioned consumption reduction. In addition, both apomorphine and LiCl activated c-Fos-like immunoreactivity (c-FLI) in the central, external, and crescent lPBN, and there was a strong correspondence between amount of c-FLI expression and strength of conditioned consumption reduction in these subnuclei. Taken together, these results support the hypothesis that the lPBN mediates apomorphine-induced conditioned consumption reduction, as is true for LiCl. Furthermore, they raise the possibility that the specific part of the lPBN mediating this conditioning effect of apomorphine and LiCl is 1 of the 3 subnuclei.

Distribution and ultrastructure of dopaminergic neurons in the dorsal motor nucleus of the vagus projecting to the stomach of the rat

Almost all parasympathetic preganglionic motor neurons contain acetylcholine, whereas quite a few motor neurons in the dorsal motor nucleus of the vagus (DMV) contain dopamine. We determined the distribution and ultrastructure of these dopaminergic neurons with double-labeling immunohistochemistry for tyrosine hydroxylase (TH) and the retrograde tracer cholera toxin subunit b (CTb) following its injection into the stomach. A few TH-immunoreactive (TH-ir) neurons were found in the rostral half of the DMV, while a moderate number of these neurons were found in the caudal half. Most of the TH-ir neurons (78.4%) were double-labeled for CTb in the half of the DMV caudal to the area postrema, but only a few TH-ir neurons (5.5%) were double-labeled in the rostral half. About 20% of gastric motor neurons showed TH-immunoreactivity in the caudal half of the DMV, but only 0.3% were TH-ir in the rostral half. In all gastric motor neurons, 8.1% were double-labeled for TH. The ultrastructure of the TH-ir neurons in the caudal DMV was determined with immuno-gold-silver labeling. The TH-ir neurons were small (20.4 x 12.4 microm), round or oval, and contained numerous mitochondria, many free ribosomes, several Golgi apparatuses, a round nucleus and a few Nissl bodies. The average number of axosomatic terminals per section was 4.0. More than half of them contained round synaptic vesicles and made asymmetric synaptic contacts (Gray's type I). Most of the axodendritic terminals contacting TH-ir dendrites were Gray's type I (90%), but a few contained pleomorphic vesicles and made symmetric synaptic contacts (Gray's type II).

Monoaminergic and peptidergic axonal projections to the vagal motor cell column of a teleost, the filefish Stephanolepis cirrhifer

In an immunohistochemical study, the vagal motor nucleus of a teleost, the filefish Stephanolepis cirrhifer, could be divided into a rostral part and a caudal part, and the former into a dorsolateral group and a ventromedial group. The dorsolateral group consisted of neurons immunoreactive for calcitonin gene-related peptide, whereas the ventrolateral-caudal group was negative for calcitonin gene-related peptide. The latter group was retrogradely labeled after dextran amine injection to the visceral ramus of the vagus nerve, suggesting that it is a general visceral efferent column, made up of parasympathetic preganglionic neurons, whereas the dorsolateral rostral group is a special visceral efferent column. In the general visceral efferent column, a dense concentration of nerve fibers immunoreactive for serotonin, tyrosine hydroxylase, cholecystokinin-8, and substance P, and a small number of fibers immunoreactive for neuropeptide Y was observed. Perikarya in contact with varicose terminals immunoreactive for these substances were frequently seen. In contrast, in the special visceral efferent column, only a moderate concentration of neuropeptide Y-immunoreactive nerve fibers and a sparse distribution of fibers immunoreactive for tyrosine hydroxylase were observed. Perikarya in contact with varicose terminals immunoreactive for these substances were rare. These results suggest that the vagal parasympathetic preganglionic neurons might receive multiple inputs of monoaminergic and peptidergic fibers involved in the regulation of the visceral organs. On the other hand, monoaminergic and peptidergic afferent fibers might be of much less significance in the activity of the special visceral efferent component of the vagus nerve.

Gastric emptying time and gastric motility in patients with Parkinson's disease

Gastrointestinal symptoms such as nausea, abdominal pain, and bloating are frequent complaints of patients with Parkinson's disease (PD). It has been postulated that impaired gastrointestinal function may contribute to the development of motor fluctuations such as delay on and no on in patients with PD. Gastrointestinal impaired function and symptoms may be associated with the disease itself or secondary to levodopa treatment. Thus, we assessed gastric emptying (GE) and gastric motility in PD patients to examine the association between clinical status and gastric function. GE and antral contraction (frequency and amplitude) were evaluated by scintigraphy in 29 patients with mild PD (Hoehn and Yahr [H&Y] stage 1.0-2.0); 22 patients with moderate PD (H&Y stage 2.5-3.0); and 22 healthy volunteers, following the ingestion of a labeled standard meal. Gastric emptying (mean +/- SD of T(1/2)) and antral contraction were not significantly different between patients with mild PD (63.4 +/- 28.8 minutes) and moderate PD (54.7 +/- 25.5 minutes). In the control group, GE was 43.4 +/- 10.8 minutes (range 29.0 - 61.0 minutes). The prevalence of delayed emptying (>61 minutes) was not significantly different in patients with mild disease (48.3%) as compared with patients with moderate disease (36.4%). Antral contraction, both frequency and amplitude, were not significantly different between patients with mild and moderate PD throughout the entire 100 minutes of the study. Untreated patients (n = 28) had mean GE T(1/2) of 59 +/- 30.6 minutes. Patients with smooth response to levodopa showed slower GE (n = 10; 73.6 +/- 25.3 minutes), while treated patients with motor response fluctuations when tested at the on state (n = 13), had much faster GE (49.3 +/- 16.2 minutes). This shortened GE in the on state was similar to the GE of normal volunteers. We conclude that gastric emptying time in patients with PD was delayed compared with control volunteers. It was even slower in patients treated with levodopa. This effect of levodopa treatment was reversed to pseudonormalization (normal GE) at the advanced stages of the disease, when patients developed motor response fluctuation. Other clinical features of PD were not associated with delayed gastric emptying.

Differential expression of catecholamine biosynthetic enzymes in the rat ventrolateral medulla

Adrenergic (C1) neurons located in the rostral ventrolateral medulla are considered a key component in the control of arterial blood pressure. Classically, C1 cells have been identified by their immunoreactivity for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH) and/or phenylethanolamine N-methyltransferase (PNMT). However, no studies have simultaneously demonstrated the expression of aromatic L-amino acid decarboxylase (AADC) and dopamine beta-hydroxylase (DBH) in these neurons. We examined the expression and colocalization of all four enzymes in the rat ventrolateral medulla using immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Retrograde tracer injected into thoracic spinal segments T2-T4 was used to identify bulbospinal neurons. Using fluorescence and confocal microscopy, most cells of the C1 group were shown to be double or triple labeled with TH, DBH, and PNMT, whereas only 65-78% were immunoreactive for AADC. Cells that lacked detectable immunoreactivity for AADC were located in the rostral C1 region, and approximately 50% were spinally projecting. Some cells in this area lacked DBH immunoreactivity (6.5-8.3%) but were positive for TH and/or PNMT. Small numbers of cells were immunoreactive for only one of the four enzymes. Numerous fibres that were immunoreactive for DBH but not for TH or PNMT were noted in the rostral C1 region. Single-cell RT-PCR analysis conducted on spinally projecting C1 neurons indicated that only 76.5% of cells that contained mRNA for TH, DBH, and PNMT contained detectable message for AADC. These experiments suggest that a proportion of C1 cells may not express all of the enzymes necessary for adrenaline synthesis.

Synaptic control of motoneuronal excitability

Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K(+) current, cationic inward current, hyperpolarization-activated inward current, Ca(2+) channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior.

Catecholaminergic mechanisms underlying neurohypophysial hormone responses to unconditioned or conditioned aversive stimuli in rats

Oxytocin release from the neurohypophysis is facilitated by systemic cholecystokinin octapeptide (CCK) administration and noxious stimuli. Oxytocin release after CCK administration is mediated by A2 noradrenergic neurones while the release after noxious stimuli appears to be mediated by A1 noradrenergic neurones. On the other hand, facilitation of vasopressin release after noxious stimuli is not dependent upon noradrenergic neurones but on dopamine receptors. Environmental stimuli previously paired with noxious stimuli (conditioned fear stimuli) or novel environmental stimuli facilitate oxytocin release and suppress vasopressin release. These neuroendocrine responses to conditioned fear stimuli, but not to novel stimuli, are impaired by central noradrenaline depletion or i.c.v. adrenoceptor antagonists. These data suggest that there are at least two types of stress responses in neuroendocrine systems, one noradrenaline dependent, and one noradrenaline independent. It is also suggested that noradrenergic neurones are functionally heterogeneous in the control of oxytocin release.

Long-lasting sensitization to the accelerating effects of amphetamine on the speed of an internal clock

Drinking in the rat occurs in bursts of rapid licking, a high frequency rhythmic behavior controlled by a neural clock located in the brain stem. We found that 3.0 mg/kg amphetamine increased the speed of licking and shifted to the left the frequency distribution of inter-lick intervals. Repeated amphetamine treatments result in long-lasting sensitization to this effect. Thus, it appears possible to produce enduring changes in the activity of a biological interval clock (or 'stopwatch') by manipulating catecholaminergic transmission. These findings may be important for an understanding of the neural basis of normal and pathological timing behavior.

Differential decreases in c-fos and aldolase C mRNA expression in the rat cerebellum after repeated administration of methamphetamine

The effects of repeated methamphetamine administration on c-fos mRNA and aldolase C (Zebrin) mRNA expression in the rat cerebellum were investigated. A single dose of methamphetamine induced c-fos mRNA expression in granule and Purkinje cells of both anterior and posterior lobes. In the posterior lobe, in particular, c-fos mRNA signals were distributed in a parasagittal organization, like Zebrin bands. Repeated methamphetamine injections reduced methamphetamine-induced c-fos mRNA signals in the anterior hemisphere and in part of the posterior vermis (lobule VII) and posterior hemisphere. Aldolase C mRNA signals in Purkinje cells decreased only in lobules where methamphetamine-induced c-fos signals were not reduced (lobules VI and IX). Therefore, differential decreases in c-fos mRNA and aldolase C mRNA expression after repeated methamphetamine administration depend upon the localization of Purkinje cells in the cerebellum. Since c-fos mRNA and aldolase C mRNA expressions are markers of excitability and the metabolic state of Purkinje cells, respectively, hypofunction of inhibitory Purkinje cells could be induced if methamphetamine is repeatedly injected. Since repeated methamphetamine administration in this experimental paradigm increased horizontal movement and the rearing activity of rats, the hemisphere of the cerebellum may be involved in development of methamphetamine-induced motor behavioral sensitization in addition to the striatum and the nucleus accumbens.

Light microscopic and ultrastructural investigation of the dopaminergic innervation of the ventrolateral outgrowth of the rat inferior olive

The ventrolateral outgrowth of the inferior olive is involved in the control of compensatory eye movement responses to optokinetic stimuli about the horizontal axis that is perpendicular to the ipsilateral anterior semicircular canal. Combining immunocytochemistry with retrograde tracing of WGA-BSA-gold, we demonstrated in the present study that this olivary subnucleus receives a substantial dopaminergic input, and that the prerubral parafascicular area and its surrounding regions form the sole source of this input. In addition, we investigated the postsynaptic distribution of the dopaminergic terminals in the inferior olive at the ultrastructural level. About a third (32%) of the dopaminergic terminals was found to make synaptic contacts in the olivary neuropil. The majority (81%) of these boutons terminated on cell bodies or extraglomerular dendrites, while the remaining terminals contacted dendritic spines inside glomeruli. In contrast, GABAergic terminals in the inferior olive formed more frequently (66%) synaptic contacts and they terminated more frequently (38%) in glomeruli. Thus, the ventrolateral outgrowth receives a dopaminergic input from the mesodiencephalic junction, and the postsynaptic distribution of this input reveals a characteristic pattern.

Co-localization of c-Fos and neurotransmitter immunoreactivities in the cat brain stem after carotid sinus nerve stimulation

To reveal neurones in the cat medulla oblongata involved in carotid baroreceptor/chemoreceptor reflexes, the distribution of c-Fos oncoprotein immunoreactivity was studied following electrical stimulation of the right carotid sinus nerve. The neurochemistry of the activated neurones was investigated using antisera to tyrosine hydroxylase, neuropeptide Y, somatostatin, and glutamate. Nitric oxide containing neurones were identified using antiserum to nitric oxide synthase (NOS) and by the histochemical localization of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase. Following sinus nerve stimulation numerous c-Fos-IR cells were detected both ipsilaterally and contralaterally in the nucleus tractus solitarii, the area postrema and throughout the ventrolateral medulla. Dual labelling studies revealed that 3.3% of c-Fos-immunoreactive cells in the nucleus tractus solitarii were also immunoreactive for tyrosine hydroxylase. The double labelled cells were scattered within the medial and ventrolateral subnuclei, predominantly rostral to obex. A higher proportion (10.3%) of c-Fos-IR cells in the ventrolateral medulla also showed tyrosine hydroxylase immunoreactivity. Caudal to obex, these were scattered in the reticular formation between the spinal trigeminal nucleus and the lateral reticular nucleus, while more rostrally they were found within the lateral reticular nucleus, the nucleus ambiguus and the lateral tegmental field. Cells expressing c-fos and reactive for glutamate, neuropeptide Y or NADPH-diaphorase (or NOS) were only rarely seen, and co-localization of c-Fos and somatostatin immunoreactivities was not seen. These results suggest that of the neurones forming pathways within the medulla activated on carotid sinus nerve stimulation, presumably mediating baro- and chemoreceptor reflexes, relatively few utilize catecholamines, glutamate, neuropeptide Y or nitric oxide as their transmitter substance.

Distribution of dopamine immunoreactivity in the rat, cat and monkey spinal cord

In the present study, the distribution of dopamine (DA) was identified light microscopically in all segments of the rat, cat, and monkey spinal cord by using immunocytochemistry with antibodies directed against dopamine. Only fibers and (presumed) terminals were found to be immunoreactive for DA. Strongest DA labeling was present in the sympathetic intermediolateral cell column (IML). Strong DA labeling, consisting of many varicose fibers, was found in all laminae of the dorsal horn, including the central canal area (region X), but with the exception of the substantia gelatinosa, which was only sparsely labeled, especially in rat and monkey. In the motoneuronal cell groups DA labeling was also strong and showed a fine granular appearance. The sexually dimorphic cremaster nucleus and Onuf's nucleus (or its homologue) showed a much stronger labeling than the surrounding somatic motoneurons. In the parasympathetic area at sacral levels, labeling was moderate. The remaining areas, like the intermediate zone (laminae VI-VIII), were only sparsely innervated. The dorsal nucleus (column of Clarke) showed the fewest DA fibers, as did the central cervical nucleus, suggesting that cerebellar projecting cells were avoided by the DA projection. In all species, the descending fibers were located mostly in the dorsolateral funiculus, but laminae I and III also contained many rostrocaudally oriented fibers. It is concluded that DA is widely distributed within the spinal cord, with few differences between species, emphasizing that DA plays an important role as one of the monoamines that influences sensory input as well as autonomic and motor output at the spinal level.

Co-localization of neurotransmitter immunoreactivities in putative nitric oxide synthesizing neurones of the cat brain stem

The distribution of nitric oxide producing neurones in the medulla oblongata of the cat was investigated using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, and nitric oxide synthase (NOS) immunohistochemistry. The pattern of staining obtained with both methods was found to be similar. Strongly diaphorase and NOS reactive neurones were present in the paramedian and lateral tegmental fields, including the regions occupied by the A1/C1 catecholamine cell groups, the nucleus ambiguus and lateral reticular nucleus, and in a number of sensory nuclei including the nucleus of the tractus solitarius and the dorsal column nuclei. The extent of co-localization of NADPH-diaphorase with a number of neuropeptides and neurotransmitters was investigated by combining NADPH-diaphorase histochemistry with immunocytochemistry for neuropeptide Y, somatostatin, glutamate, cholecystokinin and tyrosine hydroxylase. NADPH-diaphorase reaction product was observed in neurones immunoreactive for glutamate and somatostatin. These double-labelled cells were found in the paramedian region, lateral reticular field, the nucleus prepositus hypoglossi and in the rostral nucleus of the tractus solitarius. In the rostral ventrolateral medulla NADPH-diaphorase/somatostatin immunoreactive cells were found in the paragigantocellular nucleus. NADPH-diaphorase/glutamate immunoreactive cells overlapped the nucleus ambiguus, the lateral reticular nucleus and the A1/C1 catecholaminergic cell groups. In addition, a few NADPH-diaphorase/glutamate immunoreactive cells were found in the paraolivary area and gigantocellular tegmental field, in the external cuneate and infratrigeminal nuclei. The functional implications of the co-localization of nitric oxide with these neurotransmitters in areas of the medulla concerned with cardiovascular regulation is discussed.

Immunolocalization of putative neurotransmitters innervating autonomic regulating neurons (correction of neurones) of cat ventral medulla

This study investigated possible sites of contact of nerve fibers containing a range of putative neurotransmitter substances onto neurons in the cat ventral medulla oblongata concerned with autonomic, particularly cardiovascular, regulation. The parasympathetic preganglionic neurons of the nucleus ambiguous (correction of ambiguus) were identified by retrograde horseradish peroxidase tracing from the vagus nerve, and the groups of neurons in the A1 and C1 cell areas and the raphe nucleus by catecholamine enzyme or 5-hydroxytryptamine (5-HT) immunohistochemistry, respectively. Immunoreactive (-ir)nerve fibers and terminals in the vicinity if these neurons were visualized by subjecting the sections to a dual-staining technique using a brown peroxidase-diaminobenzidine reaction product and a blue alkaline phosphatase-Fast blue reaction product. By employing monochrome photography with combinations of blue and orange-red filters, it was possible to discriminate neural elements displaying one or the other reaction product, or colocalization of reaction products. The results revealed the presence of calcitonin gene-related peptide (CGRP) and galanin (GAL)-ir in some motoneurons of the nucleus ambiguus, but not in those innervating the heart via the cardiac vagus nerve. The latter group of parasympathetic efferent neurons were found to be densely innervated by fibers immunoreactive for dopamine beta-hydroxylase (DBH, indicating noradrenaline), glycine (GLY), gamma-aminobutyric acid (GABA), 5-HT, enkephalin (ENK), neuropeptide Y (NPY), substance P (SP), and thyrotropin-releasing hormone (TRH), and, to a lesser extent, by other neuropeptide-ir fibers. The catecholamine cells of the rostral C1 and caudal A1 groups showed a broadly similar pattern of innervation, most noticeably by fibers immunoreactive for DBH, GABA, 5-HT, cholecystokinin (CCK), CGRP, ENK, GAL, NPY, and SP. The 5-HT-ir neurons of the raphe nucleus, some also containing SP, TRH, ENK, or corticotropin-releasing factor (CRF)-ir, were most prominently innervated by terminals containing DBH, GABA, CCK, ENK, NPY, TRH, somatostatin (SRIF), and vasoactive intestinal polypeptide (VIP)-ir. Although the proof that these groups of neurons receive functional synaptic contacts from the immunoreactive fibers awaits further ultrastructural studies, the results do suggest that a wide range of putative transmitters may influence the activity of efferent neurons in the cat medulla controlling autonomic functions.

Immunocytochemical localization of L-dopa and dopamine in the brain of the chicken (Gallus domesticus)

A light microscopic immunocytochemical study, with antisera against dihydroxyphenylalanine (L-DOPA) and dopamine (DA), revealed the dopaergic and dopaminergic systems in the brain of the chicken (Gallus domesticus). L-DOPA- and DA-immunoreactive (ir) elements are similarly distributed throughout the entire brain. Virtually all regions of the brain contained a dense innervation by L-DOPA- and DA-immunopositive varicose fibers. The neuronal cell bodies immunoreactive for the two monoamines were confined to more restricted regions, the hypothalamus, the midbrain and the brainstem. In the hypothalamus, DA- and L-DOPA-ir neurons were subdivided into a medial periventricular and a lateral group. The medial group starts at the level of the anterior commissure, in the ventral part of the nucleus periventricularis hypothalami, and continues in a more dorsal periventricular position caudally into the dorsal tuberal hypothalamic region. Densely labeled cerebrospinal fluid contacting cells can be observed in the paraventricular organ. The lateral group consists of immunopositive neurons loosely arranged in the lateral hypothalamic area and in the nucleus mamillaris lateralis. Most of the dopaminergic cell groups, identified in the hypothalamus of mammals, could be observed in the chicken, with the exception of the tuberoinfundibular group. The majority of L-DOPA- and DA-ir perikarya is, however, situated in the mesencephalic tegmentum, in the area ventralis of Tsai and in the nucleus tegmenti pedunculo-pontinus, pars compacta, the avian homologues of, respectively, the ventral tegmental area and the substantia nigra of mammals. In the pons, dense groups of cells are found in the locus coeruleus and in the nucleus subcoeruleus ventralis and dorsalis. A few labeled cells appear in and around the nucleus olivaris superior in the most caudal part of the metencephalic tegmentum. In the medulla oblongata, L-DOPA- and DA-ir cells can be seen at the level of the nucleus of the solitary tract and in a ventrolateral complex. A comparison with tyrosine hydroxylase (TH) immunocytochemistry revealed TH-immunopositive neurons greatly outnumbering the cells exhibiting DA and L-DOPA immunoreactivity. These results are discussed in relation to catecholaminergic systems previously reported in avian species and in the mammalian brain.