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P M Pilowsky

Publications and source records attributed to P M Pilowsky.

At least 37 records · Page 2Linked to original sources
PubMed1998

The pre-Bötzinger complex and phase-spanning neurons in the adult rat.

To characterise respiratory neurons in the pre-Bötzinger complex of adult rats, extracellular recordings were made from 302 respiratory neurons in the ventral respiratory group of sodium pentobarbitone anaesthetised adult rats. Neurons were located 0 to 1.6 mm caudal to the facial nucleus, and ventral to the nucleus ambiguus. The pre-Bötzinger complex comprised expiratory neurons (22%, 22/100), inspiratory neurons (37%, 37/100) and phase-spanning neurons (41%, 41/100). In contrast, 80% (125/157) of Bötzinger neurons were expiratory, and 80% (36/45) of rostral ventral respiratory group neurons were inspiratory. Rostrocaudally, the pre-Bötzinger complex extended about 400 microns, starting at the caudal pole of the nucleus ambiguus compact formation. The pre-Bötzinger complex was also characterised by a predominance of propriobulbar neurons (81%, 13/16). Furthermore, 68% (33/48) of expiratory-inspiratory neurons found were located within the pre-Bötzinger complex. The variety of neuronal subtypes in the pre-Bötzinger complex, including many firing during the expiratory-inspiratory transition is consistent with the hypothesis that this nucleus plays a key role in respiratory rhythm generation in the adult rat.

Action Potentials↗
PubMed1998

GABA- and glutamate-immunoreactive synapses on sympathetic preganglionic neurons projecting to the superior cervical ganglion.

Our previous work suggests that virtually all of the synapses on sympathetic preganglionic neurons projecting to the rat adrenal medulla are immunoreactive for either the inhibitory amino acid, gamma-aminobutyric acid (GABA) or the excitatory amino acid, L-glutamate. To investigate whether or not this is true for other groups of sympathetic preganglionic neurons, and to determine whether or not the proportion of inputs containing each type of amino acid neurotransmitter is the same for different groups of sympathetic preganglionic neurons, we retrogradely labelled rat and rabbit sympathetic preganglionic neurons projecting to the superior cervical ganglion and used post-embedding immunogold on ultrathin sections to localise GABA- and glutamate-immunoreactivity. The cell bodies and dendrites of both rat and rabbit sympathetic preganglionic neurons projecting to the superior cervical ganglion received synapses and direct contacts from nerve fibres immunoreactive for GABA and from nerve fibres immunoreactive for glutamate. In the rat, GABA was present in 48.9% of the inputs to sympathetic preganglionic neurons projecting to the superior cervical ganglion, and glutamate was present in 51.7% of inputs. Double immunogold labelling for glutamate and GABA on the same section, as well as labelling of consecutive serial sections for the two antigens, indicated that GABA and glutamate occur in separate populations of nerve fibres that provide input to rat sympathetic preganglionic neurons projecting to the superior cervical ganglion. We now have shown that GABA or glutamate is present in virtually all of the inputs to sympathetic preganglionic neurons projecting to the superior cervical ganglion and in essentially all of the inputs to sympathetic preganglionic neurons supplying the adrenal medulla. These findings are consistent with the hypothesis that all fast synaptic transmission in central autonomic pathways may be mediated by either excitatory or inhibitory amino acids. Furthermore, we showed a statistically significant difference in the proportion of glutamate-immunoreactive inputs between sympathetic preganglionic neurons projecting to the superior cervical ganglion and sympathoadrenal neurons (data from Llewellyn-Smith et al. [Llewellyn-Smith, I.J., Phend, K.D., Minson, J.B., Pilowsky, P.M., Chalmers, J.P., 1992. Glutamate immunoreactive synapses on retrogradely labelled sympathetic neurons in rat thoracic spinal cord. Brain Res. 581, 67-80]), with preganglionics supplying the adrenal medulla receiving more excitatory inputs than those supplying the superior cervical ganglion. This increased excitatory input to sympathoadrenal neurons may explain the predominant activation of these neurons following baroreceptor unloading.

Animals↗
PubMed1998

Pre-embedding staining for GAD67 versus postembedding staining for GABA as markers for central GABAergic terminals.

Pre-embedding immunocytochemistry for the active form of glutamate decarboxylase (GAD67) and postembedding staining for gamma-aminobutyric acid (GABA) were compared as markers for central GABAergic terminals in the phrenic motor nucleus, in which phrenic motor neurons had been retrogradely labeled with cholera toxin B-horseradish peroxidase. Nerve terminals with or without GAD67 immunoreactivity were identified in one ultrathin section. GABA was localized with immunogold in an adjacent section after etching and bleaching. GABA labeling density was assessed over 519 GAD67-positive and GAD67-negative nerve terminals in the phrenic motor nucleus. Frequency histograms showed that statistically higher densities of gold particles occurred over most GAD67-positive terminals. However, some GAD67-negative terminals also showed high densities of gold particles, and some GAD67-positive terminals showed low densities. Preabsorption of the anti-GABA antibody with a GABA-protein conjugate, but not with other amino acid-protein conjugates, significantly reduced gold labeling over both GAD67-positive and GAD67-negative terminals. These results show that the presence of GAD67 immunoreactivity correlates strongly with high densities of immunogold labeling for GABA in nerve terminals in the phrenic motor nucleus. Preabsorption controls indicate that authentic GABA was localized in the postembedding labeling procedure. Only a small proportion of intensely GABA-immunoreactive terminals lack GAD67, suggesting that both GAD67 and GABA are reliable markers of GABAergic nerve terminals.

Animals↗
PubMed1997

c-fos identifies GABA-synthesizing barosensitive neurons in caudal ventrolateral medulla.

Hypertension in the conscious rat, elicited by i.v. infusion of phenylephrine, evoked expression of the immediate early gene c-fos in discrete groups of brain stem neurons. Fos-immunoreactive neurons were located in the caudal ventrolateral medulla (CVLM); others were located in the nucleus of the tractus solitarius (NTS). Because of their sensitivity to alterations in arterial pressure, these neurons are likely to subserve the arterial baroreceptor reflex. The aim of this study was to identify the brain stem projections and the neurotransmitter content of the barosensitive CVLM neurons using neuronal tracing and immunohistochemistry. Some of the barosensitive CVLM neurons projected directly to the rostral ventrolateral medulla (RVLM), and many contained the GABA synthesizing enzyme, glutamic acid decarboxylase (GAD). Other CVLM neurons, containing markers of glutamate or catecholamine synthesis, were insensitive to baroreceptor stimulation. This study delineates neuronal pathways acting in the arterial baroreceptor reflex and identifies precisely GABA-synthesizing CVLM neurons as the source of inhibitory input to the RVLM.

Animals↗
PubMed1997

Neurokinin-1 receptor-immunoreactive sympathetic preganglionic neurons: target specificity and ultrastructure.

Substance P is involved in cardiovascular control at the spinal cord level, where it acts through neurokinin-1 receptors. In this study we used immunocytochemistry and retrograde tracing to investigate the presence of the neurokinin-1 receptor and its ultrastructural localization in rat sympathetic preganglionic neurons that project to the superior cervical ganglion or the adrenal medulla. Immunofluorescence for the neurokinin-1 receptor outlined the somatic and dendritic surfaces of neurons in autonomic subnuclei of spinal cord segments T1-T12, whereas immunofluorescence for the tracer, cholera toxin B subunit, filled retrogradely labelled cells. There was a significant difference in the proportion of neurokinin-1 receptor-immunoreactive sympathetic preganglionic neurons supplying the superior cervical ganglion and the adrenal medulla. Thirty-eight percent of the neurons that projected to the superior cervical ganglion were immunoreactive for the neurokinin-1 receptor compared to 70% of neurons innervating the adrenal medulla. Of neurons projecting to the superior cervical ganglion, significantly different proportions showed neurokinin-1 receptor immunoreactivity in spinal cord segment T1 (15%) versus segments T2 T6 (45%). At the ultrastructural level, neurokinin-1 receptor staining occurred predominantly on the inner leaflets of the plasma membranes of retrogradely labelled sympathetic preganglionic neurons. Deposits of intracellular label were often observed in dendrites and in the rough endoplasmic reticulum and Golgi apparatus of cell bodies. Neurokinin-1 receptor immunoreactivity was present at many, but not all, synapses as well as at non-synaptic sites, and occurred at synapses with substance P-positive as well as substance P-negative nerve fibres. Only 37% of the substance P synapses occurred on neurokinin-1-immunoreactive neurons in the intermediolateral cell column. These results show that presence of the neurokinin-1 receptor in sympathetic preganglionic neurons is related to their target. The ultrastructural localization of the receptor suggests that sympathetic preganglionic neurons may be affected (i) by substance P released at neurokinin-1 receptor-immunoreactive synapses, (ii) by other tachykinins (e.g., neurokinin A), which co-localize in substance P fibres in the intermediolateral cell column, acting through other neurokinin receptors, and (iii) by substance P that diffuses to neurokinin-1 receptors from distant sites.

Adrenal Medulla↗
PubMed1997

Respiratory activity of the rat posterior cricoarytenoid muscle.

An anatomic and electrophysiological study of the rat posterior cricoarytenoid (PCA) muscle is described. The intramuscular nerve distribution of the PCA branch of the recurrent laryngeal nerve was demonstrated by a modified Sihler's stain. The nerve to the PCA was found to terminate in superior and inferior branches with a distribution that appeared to be confined to the PCA muscle. Electromyography (EMG) recordings of PCA muscle activity in anesthetized rats were obtained under stereotaxic control together with measurement of phrenic nerve discharge. A total of 151 recordings were made in 7 PCA muscles from 4 rats. Phasic inspiratory activity with a waveform similar to that of phrenic nerve discharge was found in 134 recordings, while a biphasic pattern with both inspiratory and post-inspiratory peaks was recorded from random sites within the PCA muscle on 17 occasions. The PCA EMG activity commenced 24.6 +/- 2.2 milliseconds (p < .0001) before phrenic nerve discharge. The results are in accord with findings of earlier studies that show that PCA muscle activity commences prior to inspiratory airflow and diaphragmatic muscle activity. The data suggest that PCA and diaphragm motoneurons share common or similar medullary pre-motoneurons. The earlier onset of PCA muscle activity may indicate a role for medullary pre-inspiratory neurons in initiating PCA activity.

Animals↗
PubMed1996

Vesicle shape and amino acids in synaptic inputs to phrenic motoneurons: do all inputs contain either glutamate or GABA?

Varicosities that made synapses or direct contacts with retrogradely labelled rat phrenic motoneurons were examined for their content of immunoreactivity for either glutamate or glutamate decarboxylase, the enzyme involved in synthesis of gamma-aminobutyric acid (GABA). Phrenic motoneurons were identified by retrograde tracing from the diaphragm with cholera toxin B subunit conjugated to horseradish peroxidase. Cell bodies and medium-sized to large dendrites were labelled. Preembedding immunocytochemistry identified glutamate decarboxylase-immunoreactive nerve fibres; glutamate-immunoreactive nerve terminals were identified using postembedding immunogold labelling of ultrathin sections. The presence of glutamate- or glutamate decarboxylase immunoreactivity in nerve terminals was correlated with the morphology of the synaptic vesicles. Two major classes of nerve terminals were identified. Nerve terminals with round (presumably spherical) synaptic vesicles (S terminals) comprised 55% of synapses and contacts on phrenic motoneuron somata and 58% of synapses and direct contacts with dendrites. Nerve terminals with flattened synaptic vesicles (F terminals) comprised 42% of synapses direct contacts with somata and 41% of synapses and direct contacts with dendrites. Analysis of immunogold-labelled sections showed that S terminals contained statistically higher levels of glutamate immunoreactivity than F terminals. At the light microscope level, many glutamate decarboxylase-immunoreactive nerve terminals surrounded retrogradely labelled motoneurons. Varicosities with glutamate decarboxylase immunoreactivity made 33% of all synapses and direct contacts on somata, and 33% of synapses and direct contacts with dendrites of the retrogradely labelled phrenic motoneurons. Flattened synaptic vesicles were present in those glutamate decarboxylase-immunoreactive nerve terminals in which synaptic vesicle morphology could be judged. An additional 10% of all nerve terminals were of the F type, but were not glutamate decarboxylase-immunoreactive. Three percent of terminals on somata and 1% of nerve terminals on dendrites could not be classified as S or F types. These findings suggest that more than 90% of all inputs to phrenic motoneuron cell bodies and proximal dendrites could contain either GABA or glutamate. Some of these glutamatergic and GABAergic nerve fibres undoubtedly represent the source of inspiratory drive to, or expiratory inhibition of, phrenic motoneurons.

Animals↗
PubMed1996

Tachycardia after glutamate injection in rat spinal cord is not blocked by kynurenate or mimicked by metabotropic agonists.

1. We have used microinjections of glutamate, an ionotropic excitatory amino acid receptor antagonist (kynurenate) and selective ionotropic (NMDA and kainate) and metabotropic (1S-3R-ACPD, trans-ACPD and L-AP4) receptor agonists in the thoracic IML of the rat to define the receptors mediating the tachycardia produced by excitatory amino acid antagonists. 2. Injection of glutamate (delta heart rate = 76 +/- 8 beats/min n = 16), NMDA (delta heart rate = 116.5 +/- 5 beats/min n = 6) or kainate (delta heart rate = 92 +/- 22 beats/min n =6 evokes a tachycardia when injected into the thoracic intermediolateral column. Kynurenate blocked the response to NMDA (-2% of initial response) and markedly attenuated the response to kainate (14% of initial response) but did not alter the response to glutamate (106% of initial response). 3. IS-3R-ACPD did not elicit a tachycardia when injected into the thoracic intermediolateral column and neither trans-ACPD nor L-AP4 induced a tachycardia after kynurenate injection into the thoracic intermediolateral column. 4. Thus stimulation of either NMDA or AMPA/kainate receptors elicits tachycardia in rat thoracic spinal cord but glutamate also activates another receptor type to elicit a tachycardia. The lack of a tachycardia when trans-ACPD, 1S-3R-ACPD or L-AP4 were injected into the thoracic spinal cord suggests that the kynurenate resistant tachycardia elicited by glutamate is not mediated by metabotropic receptors. The kynurenate resistant tachycardia elicited by glutamate is not mediated by any of the known excitatory amino acid receptor types.

Aminobutyrates↗
PubMed1995

Thyrotropin-releasing hormone-immunoreactive varicosities synapse on rat phrenic motoneurons.

The relationship between retrogradely labelled or intracellularly filled phrenic motoneurons and varicosities containing thyrotropin-releasing hormone immunoreactivity was investigated in rats by light and electron microscopy. Phrenic motoneurons were identified via retrograde tracing from the diaphragm with cholera toxin B subunit, which was followed by immunocytochemistry to visualise retrogradely labelled motoneurons and thyrotropin-releasing hormone-immunoreactive nerve fibres in their vicinity. At the light microscopic level, varicose thyrotropin-releasing hormone-immunoreactive nerve fibres were distributed sparsely in the phrenic motor nucleus, with some axons surrounding retrogradely labelled motoneurons. In separate intracellular experiments, four phrenic motoneurons identified by antidromic activation from the C5 phrenic nerve root were subsequently filled with Neurobiotin, and nerve fibres that contained thyrotropin-releasing hormone immunoreactivity were identified by immunocytochemistry. The numbers and locations of thyrotropin-releasing hormone-immunoreactive varicosities that were closely appeared to the intracellularly labelled motoneurons were mapped using a camera lucida technique. Close appositions by thyrotropin-releasing hormone-immunoreactive varicosities were seen on somata as well as on proximal and distal dendrites. The closely apposed varicosities were usually present in tight clusters, which were formed by single varicose axons. However, the distribution was nonuniform, in that some dendrites did not receive any close appositions. Ultrastructural analysis of random ultrathin sections through retrogradely labelled neurons showed that varicosities with thyrotropin-releasing hormone immunoreactivity made 1.8% of all synapses and direct contacts on somata and 2.3% of synapses and contacts with dendrites of the retrogradely labelled phrenic motoneurons. The results of these experiments suggest that thyrotropin-releasing hormone-immunoreactive varicosities provide similar numbers of inputs to both the somata and dendrites of phrenic motoneurons. These thyrotropin-releasing hormone-containing inputs seen via light and electron microscopy could modulate the excitability of phrenic motoneurons.

Animals↗
PubMed1995

Bulbospinal sympatho-excitatory neurons in the rat caudal raphe.

OBJECTIVES: To explore the rat caudal raphe nuclei for neurons that respond to activation of baroreceptor nerves and that have a spinal axon, and to compare the behavioural properties of barosensitive bulbospinal neurons in the rat caudal raphe with the properties of barosensitive bulbospinal neurons in the rostral ventrolateral medulla. DESIGN: Extracellular unit recordings were obtained from an area extending up to 1.0 mm caudally from the caudal edge of the facial nucleus. Two sites were explored: the rostral ventrolateral medulla and the midline. MATERIALS AND METHODS: Single-unit recordings were made in anaesthetized (75 mg/kg chloral hydrate and 30 mg/kg sodium pentobarbitone then 3-6 mg intravenously as required), immobilized (2 mg pancuronium as required) Sprague-Dawley rats. Central respiratory drive was recorded from phrenic nerve discharge. The barosensitivity of single units was assessed by R-wave triggered histograms and by histograms of their responses to aortic nerve stimulation or to intravenous injection of phenylephrine. Nociceptors were activated by a brief pinch of the tail. RESULTS: Eleven spontaneously active units in the midline that were inhibited by baroreceptor stimulation and had a spinal axon were studied. Respiratory modulation was present and was predominantly inspiratory. Barosensitive neurons in the rostral ventrolateral medulla were activated by nociceptive inputs; midline barosensitive neurons were not. CONCLUSIONS: The behavioural characteristics of midline neurons differ from those of the bulbospinal barosensitive neurons in the rostral ventrolateral medulla, indicating that raphe spinal neurons have different sets of afferent inputs and may subserve to a distinct physiological role. The present paper is the first report of bulbospinal neurons in the rat caudal raphe that are inhibited by activation of arterial baroreceptors.

Adrenergic Fibers↗
PubMed1994

Disinhibition of the rostral ventral medulla increases blood pressure and Fos expression in bulbospinal neurons.

The GABA agonist muscimol, injected into the depressor area of the caudal ventrolateral medulla, increased blood pressure and increased the expression of the immediate early gene c-fos in the rostral ventral medulla (RVM) of the rat. The number of Fos-immunoreactive (Fos-IR) neurons seen in the RVM was increased 3-fold after muscimol compared to Fos-IR after vehicle treatment. In the rostral aspect of the RVM approximately half of the Fos-IR neurons were identified as spinally projecting after the injection of the retrograde tracer cholera toxin B subunit into the upper thoracic spinal cord. These bulbospinal Fos-IR neurons were identified in the lateral aspects of the RVM, in the area where baroreceptor-sensitive neurons have been identified in electrophysiological studies, and also in more medial areas of the RVM. Fos-IR neurons were also identified in the intermediolateral cell column of the thoracic spinal cord after muscimol injection, but were rarely observed in this area after vehicle treatment. This study demonstrates the functional connectivity of the caudal and rostral areas of the medulla oblongata and the spinal cord, supporting the view that the caudal ventrolateral medulla contains neurons that provide a tonic inhibitory control over neurons in the RVM and that, in turn, the spinally projecting neurons in the RVM provide an excitatory input to the spinal cord sympathetic preganglionic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Bulbospinal neuropeptide Y-immunoreactive neurons in the rat: comparison with adrenaline-synthesising neurons.

Immunohistochemistry and retrograde tracing using cholera toxin B subunit colloidal gold (CTB-gold) has been used to identify neurons in the medulla that contain neuropeptide Y and project to the area of the intermediolateral cell column in either the upper (T2-T4) or the lower (T8-T9) thoracic spinal cord. The rostrocaudal distributions of neuropeptide Y neurons and neuropeptide Y/CTB-gold neurons have been compared with the distributions of adrenaline-synthesising, phenylethanolamine N-methyltransferase-containing neurons and phenylethanolamine N-methyltransferase/CTB-gold neurons visualised in adjacent sections. In particular areas of the rostral medulla similarities in the numbers and distributions of neuropeptide Y neurons and phenylethanolamine N-methyltransferase neurons suggested a coexistence of the peptide within the catecholamine neurons. However, at the most rostral levels of the rostral ventral medulla, the large numbers of phenylethanolamine N-methyltransferase neurons were not matched by similar numbers of neuropeptide Y neurons, so that the phenylethanolamine N-methyltransferase neurons in this area could not all contain neuropeptide Y. In the rostral ventral medulla fewer neuropeptide Y/CTB-gold neurons than phenylethanolamine N-methyltransferase/CTB-gold neurons were observed, so that these bulbospinal peptide neurons might define a subset of the phenylethanolamine N-methyltransferase/CTB-gold neurons, accounting for 25% of the total phenylethanolamine N-methyltransferase bulbospinal projection from the rostral ventral medulla. Other neuropeptide Y/CTB-gold neurons in the dorsal medulla are also likely to contain phenylethanolamine N-methyltransferase. Finally, a population of neuropeptide Y/CTB-gold neurons was identified in the caudal ventral medulla, these neurons appear not to contain catecholamine synthesising enzymes.

Animals↗
PubMed1994

ANTISENSE oligonucleotides: a new tool in neuroscience.

1. Recent studies have shown that gene expression can be selectively attenuated by administration of short sequences of nucleotides (oligonucleotides) that are complementary to a portion of messenger RNA coding for a particular gene product. 2. This technique is known as ANTISENSE, because the oligonucleotides are complementary to the mRNA which has the same sequence as the SENSE strand of DNA. 3. In the present review we focus, after a brief discussion of gene expression and mechanisms of action of ANTISENSE, on the methodological aspects of ANTISENSE experiments in neuroscience. In particular, we address the advantages, disadvantages and controls for the ANTISENSE technique, as well as the choice, design, mode of delivery, dose and storage of ANTISENSE oligonucleotides.

Animals↗
PubMed1992

Glutamate-immunoreactive synapses on retrogradely-labelled sympathetic preganglionic neurons in rat thoracic spinal cord.

Retrograde tracing with cholera toxin B subunit (CTB) combined with post-embedding immunogold labelling was used to demonstrate the presence of glutamate-immunoreactive synapses on sympathetic preganglionic neurons that project to the adrenal medulla or to the superior cervical ganglion in rat thoracic spinal cord. At the electron microscope level, glutamate-immunoreactive synapses were found on retrogradely labelled nerve cell bodies and on dendrites of all sizes. Two-thirds of the vesicle-containing axon profiles that were directly apposed to, or synapsed on, CTB-immunoreactive sympathoadrenal neurons were glutamate positive. The proportion of glutamate-immunoreactive contacts and synapses on sympathoadrenal neurons decreased to zero when the anti-glutamate antiserum was absorbed with increasing concentrations of glutamate from 0.1 mM to 10 mM. Double immunogold labelling for glutamate and gamma-aminobutyric acid (GABA) showed that glutamate-immunoreactive profiles did not contain GABA and that GABA-immunoreactive profiles did not contain glutamate. These results suggest that glutamate is the major excitatory neurotransmitter to sympathoadrenal neurons and possibly to other sympathetic preganglionic neurons in the intermediolateral cell column of the spinal cord.

Animals↗
PubMed1991

There are few catecholamine- or neuropeptide Y-containing synapses in the intermediolateral cell column of rat thoracic spinal cord.

1. A quantitative electron microscopic immunocytochemical technique was used to assess the number of synapses immunoreactive for tyrosine hydroxylase (TH), phenylethanolamine N-methyl-transferase (PNMT) and neuropeptide Y (NPY) in the intermediolateral cell column in segments T2 and T3 of rat thoracic spinal cord. 2. TH synapses comprised about 5%; PNMT synapses 1-2%; and NPY synapses 1-2% of the total number of synapses in the intermediolateral cell column. All three types of synapses were predominantly or exclusively on dendrites. 3. Our results suggest that catecholamine/NPY neurons may not provide a major synaptic input to sympathetic preganglionic neurons in rat upper thoracic spinal cord.

Animals↗
PubMed1990

An intracellular study of respiratory neurons in the rostral ventrolateral medulla of the rat and their relationship to catecholamine-containing neurons.

Intracellular recording and labelling with Lucifer yellow of respiratory neurons in the rostral ventrolateral medulla were carried out in urethane-anaesthetised rats. A combined immunofluorescence and immunoperoxidase technique enabled an assessment of the tyrosine hydroxylase immunoreactivity, as well as an examination of the morphology of inspiratory and expiratory neurons in this part of the medulla oblongata. The results demonstrate: a) that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine-containing neurons of the C1 cell group, but are not themselves catecholamine-containing; b) that many non-spinally projecting respiratory neurons have axonal arborisations within the ventrolateral medulla in the same region as the C1 cell group, other respiratory neurons, and neurons reported to have a cardiovascular function; and c) that the dendrites of respiratory neurons in this region radiate throughout the ventrolateral medulla and frequently approach the ventral surface.

Animals↗
PubMed1990

Serotonin immunoreactive boutons form close appositions with respiratory neurons of the dorsal respiratory group in the cat.

The aim of this study was to examine the location of serotonin immunoreactive boutons on both the soma and dendrites of neurons in the dorsal respiratory group by using a combination of intracellular recording and labelling and immunohistochemistry. Inspiratory neurons in the ventrolateral nucleus of the solitary tract (vl-NTS) were intracellularly labelled with horseradish peroxidase (HRP) in anaesthetised adult cats. The morphology of 23 neurons, all antidromically activated from the contralateral C3 spinal segment, was examined. Six neurons displayed pronounced dendritic arborizations outside the vl-NTS, with prominent dorsal and/or medial projections. The dendrites of the remaining neurons were almost entirely confined to the vl-NTS. Intramedullary axon collaterals were detected in four of nineteen examined axons. Serotoninergic fibres were immunohistochemically demonstrated in the NTS, and the apposition of immunoreactive boutons to the HRP-filled neurons examined at the light microscopic level. Boutons were identified in close apposition with the somata, proximal and distal dendrites of these neurons. However, the density of contacts was found to be substantially less than in a previous study of phrenic motoneurons (Lipski et al: Soc. Neurosci. Abst. 14:379, '88; Pilowsky et al: J. Neurosci. in press, '90). The relative paucity of contacts of serotonin immunoreactive boutons with premotor inspiratory neurons of the dorsal respiratory group indicates that the serotoninergic system affects respiratory pathways mainly at the level of respiratory motoneurons or at brainstem sites outside the vl-NTS.

Action Potentials↗