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Biomedical subjects

D A Hopkins

Publications and source records attributed to D A Hopkins.

At least 37 records · Page 2Linked to original sources
PubMed1997

Constitutive expression of the 27-kDa heat shock protein (Hsp27) in sensory and motor neurons of the rat nervous system.

In this study, the constitutive expression of the 27-kDa heat shock protein (Hsp27) in the adult rat central nervous system has been examined by immunohistochemistry and by two-dimensional gel Western blot analysis. Hsp27 immunoreactivity was observed primarily in motoneurons of cranial nerve nuclei and spinal cord, and in primary sensory neurons and their central processes. Also, Hsp27 immunoreactivity was present in neurons of the arcuate nucleus and of the reticular formation. However, only a subset of these neurons was Hsp27-immunoreactive. Most general somatic efferent motoneurons of the hypoglossal nucleus and spinal motor columns and most special visceral efferent motoneurons of the cranial nerve nuclei were Hsp27-positive. In contrast, fewer general somatic efferent motoneurons for eye muscles were Hsp27-positive, and only a small proportion of general visceral efferent neurons, i.e., parasympathetic and sympathetic preganglionic neurons, were stained for Hsp27. Many pseudounipolar sensory neurons were Hsp27-immunoreactive, and the patterns of staining in central sensory nuclei suggested that specific subpopulations of sensory neurons contained Hsp27. The cellular distribution of Hsp27 was uniform throughout the cytoplasm, including the perikaryon, axon and dendrites, the latter often exhibiting varicosities or beading in distal processes. Western blot analyses revealed that at least three phosphorylated isoforms of Hsp27 were present in the spinal cord. These results suggest that constitutively expressed Hsp27 may be related to functional subpopulations of motoneurons and primary sensory neurons.

Animals↗
PubMed1997

Anatomy of medullary and peripheral autonomic neurons innervating the neonatal porcine heart.

Gross and microscopic anatomical investigations were carried out in 14 piglets aged from 4 to 66 days. True Blue (7-50 microliters) and Diamidino Yellow (7-50 microliters) were injected individually into 2 different cardiac sites (the right atrial ganglionated plexus, the inferior vena cava, inferior atrial ganglionated plexus, the right atrium or the right ventricle). Gross anatomy: Globular superior cervical and nodose ganglia, elongated stellate ganglia, multiple small middle cervical ganglia and multiple small mediastinal ganglia along the course of cardiopulmonary nerves were identified. Microscopic anatomy: Neurons innervating specific cardiac regions or intrinsic cardiac ganglionated plexuses were distributed relatively evenly among stellate (primarily in their cranial poles) and middle cervical ganglia bilaterally, fewer labeled neurons being located in the superior cervical and mediastinal ganglia bilaterally. Parasympathetic efferent preganglionic neurons associated with either intrinsic cardiac ganglionated plexus studied were identified primarily throughout the ventrolateral region (the external formation) of the nucleus ambiguus bilaterally. Labeled neurons were also identified throughout the right and left nodose ganglia. Individual neurons did not project axons to different cardiac regions, as no double-labeled neurons were identified. No correlation between age and the numbers and locations of labeled neurons was apparent. Thus, porcine sympathetic efferent neurons which innervate individual cardiac regions, including intrinsic cardiac ganglionated plexuses, lie scattered primarily throughout the right and left mediastinal and middle cervical ganglia as well as the cranial poles of stellate ganglia at birth, apparently changing little during the first 2 months of age. Porcine cardiac parasympathetic efferent preganglionic neurons are located primarily in the external formation of the nucleus ambiguus bilaterally at birth. The numbers of afferent cardiac neurons distributed throughout the nodose ganglia bilaterally also change little during that time. It is concluded that most of the autonomic neurons which innervate the heart are in place at birth.

Anatomy, Artistic↗
PubMed1997

Evidence that hepatitis C virus resistance to interferon is mediated through repression of the PKR protein kinase by the nonstructural 5A protein.

Hepatitis C virus (HCV) is the major cause of non-A non-B hepatitis and a leading cause of liver dysfunction worldwide. While the current therapy for chronic HCV infection is parenteral administration of type 1 interferon (IFN), only a fraction of HCV-infected individuals completely respond to treatment. Previous studies have correlated the IFN sensitivity of strain HCV-1b with mutations within a discrete region of the viral nonstructural 5A protein (NS5A), termed the interferon sensitivity determining region (ISDR), suggesting that NS5A may contribute to the IFN-resistant phenotype of HCV. To determine the importance of HCV NS5A and the NS5A ISDR in mediating HCV IFN resistance, we tested whether the NS5A protein could regulate the IFN-induced protein kinase, PKR, a mediator of IFN-induced antiviral resistance and a target of viral and cellular inhibitors. Using multiple approaches, including biochemical, transfection, and yeast genetics analyses, we can now report that NS5A represses PKR through a direct interaction with the protein kinase catalytic domain and that both PKR repression and interaction requires the ISDR. Thus, inactivation of PKR may be one mechanism by which HCV avoids the antiviral effects of IFN. Finally the inhibition of the PKR protein kinase, by NS5A is the first described function for this HCV protein.

Antiviral Agents↗
PubMed1997

Gross and microscopic anatomy of the human intrinsic cardiac nervous system.

BACKGROUND: The extent and locations of intrinsic cardiac ganglia on the human heart were investigated to facilitate studying their function. METHODS: The locations and number of major intrinsic cardiac ganglia were determined in six human hearts by means of microdissection following methylene blue staining. Light and electron microscopic analyses were performed on right atrial and cranial medial ventricular ganglia obtained from 12 other human hearts. RESULTS: Gross anatomy: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were observed consistently in five atrial and five ventricular regions. Occasional ganglia were located in other atrial and ventricular regions. Atrial ganglionated plexuses were identified on 1) the superior surface of the right atrium, 2) the superior surface of the left atrium, 3) the posterior surface of the right atrium, 4) the posterior medial surface of the left atrium (the latter two fuse medially where they extend anteriorly into the interatrial septum), and 5) the inferior and lateral aspect of the posterior left atrium. Ventricular ganglionated plexuses were located in fat 1) surrounding the aortic root, 2) at the origins of the right and left coronary arteries (the latter extending to the origins of the left anterior descending and circumflex coronary arteries), 3) at the origin of the posterior descending coronary artery, 4) adjacent to the origin of the right acute marginal coronary artery, and 5) at the origin of the left obtuse marginal coronary artery. Microscopic anatomy: Ganglia ranged in size from those containing a few neurons to large ganglia measuring up to 0.5 x 1 mm. The human heart is estimated to contain more than 14,000 neurons. Neuronal somata varied in size and shape. Many axon terminals in intrinsic cardiac ganglia contained large numbers of small, clear, round vesicles that formed asymmetrical axodendritic synapses, whereas a few axons contained large, dense-cored vesicles. CONCLUSIONS: The human intrinsic cardiac nervous system is distributed more extensively than was considered previously, most of its ganglia being located on the posterior surfaces of the atria and superior aspect of the ventricles. Each ganglion therein contains a variety of neurons that are associated with complex synaptology.

Adult↗
PubMed1996

Nitric oxide synthase, cGMP, and NO-mediated cGMP production in the olfactory bulb of the rat.

High levels of nitric oxide synthase and cyclic 3',5'-guanosine monophosphate (cGMP) in the olfactory bulb suggest that nitric oxide, acting as a diffusible intercellular messenger molecule inducing increased synthesis of cGMP, plays an important role in olfaction. The localization of cGMP after sodium nitroprusside stimulation of in vitro slices of rat olfactory bulb was compared with the distribution of nicotinamide adenine dinucleotide phosphatediaphorase, nitric oxide synthase, and glial fibrillary acidic protein. cGMP was detected immunohistochemically in cryostat sections. In the presence of the phosphodiesterase blocker isobutyl methylxanthine, cGMP was present in neurons in the glomerular layer, axons in the external and internal plexiform layers, and in a few somata and axons of the granule cell layer. This staining was blocked by NG-nitro-L-arginine methylester hydrochloride or hemoglobin. After sodium nitroprusside stimulation, the olfactory nerve layer was intensely stained, as were the glomeruli and periglomerular cells. In the external plexiform layer, axonal staining was increased substantially, and there were occasional multipolar cGMP-positive neurons. In the internal plexiform and granule cell layers, axonal staining was greatly increased. Many granule cells were also cGMP positive after sodium nitroprusside stimulation. cGMP and nitric oxide synthase-positive neuronal elements overlapped in the glomerular and granule cell layers, but staining was not colocalized, cGMP was not found in astrocytes. The glutamatergic antagonists D-2-amino-5-phosphonovalerate and 6-cyano-7-nitroquinoxaline caused differential inhibition of cGMP accumulation in layers of the olfactory bulb. These findings support the hypothesis that nitric oxide is an intercellular messenger in the olfactory bulb (Breer and Shepherd [1993] Trends Neurosci. 16:5-9).

Animals↗
PubMed1996

Ultrastructure and synaptology of the nucleus ambiguus in the rat: the semicompact and loose formations.

The fine structure of the pharyngomotor semicompact and laryngomotor loose formations of the rat nucleus ambiguus was studied in single and serial sections by means of light and electron microscopy. Motoneurons and their dendrites were identified after retrograde labelling by injections of neuroanatomical tracers into pharyngeal and laryngeal muscles or nerves. Pharyngeal motoneurons measured 39 x 29 microns and had 2-25 axosomatic synapses per somatic profile, representing an estimated average of 182 synapses per soma. Laryngeal motoneurons measured 42 x 30 microns with 6-33 synapses per profile, or an average of 339 synapses per soma. In both subdivisions, axon terminals that contained round vesicles and formed symmetric junctions and terminals that contained pleomorphic vesicles and formed symmetric junctions were distributed in approximately equal proportions on somata and dendrites, forming over 90% of the synapse population. A small percentage (2-8%) of synapses had a subsurface cistern situated below the axon terminal (C type). Small, atypical motoneurons measuring 15 x 5 microns with an invaginated nucleus were also present in both subdivisions. The ultrastructure and synaptology of pharyngeal and laryngeal motoneurons are characterized by similarities to those of spinal motoneurons and by their relatively large numbers of axosomatic synapses in comparison to esophageal motoneurons of the compact formation of the nucleus ambiguus.

Animals↗
PubMed1996

Effects of the 3',5'-phosphodiesterase inhibitors isobutylmethylxanthine and zaprinast on NO-mediated cGMP accumulation in the hippocampus slice preparation: an immunocytochemical study.

The effect of inhibition of 3',5'-phosphodiesterase (PDE) activity on the cGMP accumulation was studied in control and nitric oxide (NO) stimulated hippocampal slices incubated in vitro using immunohistochemical visualisation of cGMP. Isobutylmethylxanthine (IBMX) was used as a non-selective PDE inhibitor and zaprinast was used as a selective inhibitor of cGMP-specific PDE activity. In the absence of PDE inhibitors cGMP-immunoreactivity (cGMP-IR) was found in blood vessel walls only. After incubation with the NO-donor sodium nitroprusside (SNP) cGMP-IR was found in a few isolated varicose fibres which were distributed throughout the slice. Incubation in the presence of either 1 mM IBMX or 10 microM zaprinast resulted in cGMP-IR in small numbers of varicose fibres distributed throughout the hippocampal slice. SNP in combination with IBMX resulted in cGMP-IR in small numbers multitude of varicose fibres throughout the slice; occasionally cell somata were observed. After incubation with SNP and zaprinast cGMP-IR was found in varicose fibres, although with a more restricted distribution and less numerous than in the presence of IBMX. In the latter combination, varicose fibres were observed predominantly in the CA2/CA3 region and in the stratum lacunosum molecular of the hippocampus, and cell somata were occasionally observed throughout the hippocampus. The differential distribution of cGMP-IR in the presence of different PDE inhibitors is consistent with the notion that there are regional differences in the localization of cGMP hydrolyzing enzymes in the hippocampus.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Morphological and immunohistochemical properties of primary long-term cultures of adult guinea-pig ventricular cardiomyocytes with peripheral cardiac neurons.

Long-term (2-12 weeks) cultures of adult guinea-pig ventricular myocytes, cocultured with neurons derived from stellate or intrinsic cardiac ganglia, retain their functional properties (Horackova et al., 1993, 1994, 1995). The present study was designed to investigate the morphological and immunochemical properties of such neurons and their associated cardiomyocytes. Cultured myocytes studied by means of phalloidin-rhodamine (for F-actin) and an antibody raised against myomes revealed parallel myofibrils with striations typical of rod-shaped cardiomyocytes, even while myocytes changed from cylindrical to flattened form as they established intercellular contacts. Microtubular networks, identified by alpha-tubulin DM1A antibody, were arrayed longitudinally in myofibrils, being especially prominent during the formation of intercellular contacts between myocytes. Histochemically identified adult peripheral autonomic neurons cultured alone or with myocytes displayed a variety of shapes. alpha-Tubulin staining was associated with the somata and neurites of various-shaped neurons whether cultured alone or with myocytes. Cultured neurons derived from stellate and intrinsic cardiac ganglia also exhibited staining for the general neuronal marker PGP 9.5 (protein gene product 9.5), and for specific markers of the following neurochemicals: tyrosine hydroxylase, acetylcholinesterase, choline acetyltransferase, neuropeptide Y, vasoactive intestinal peptide, calcitonin gene-related peptide, bradykinin, oxytocin, and NADPH-diaphorase. These data indicate that: (a) adult ventricular myocytes cocultured with intrathoracic neurons retain the structural properties of adult myocytes found in vivo; (b) intrinsic cardiac and extrinsic intrathoracic neurons cultured alone or with cardiomyocytes display morphological characteristics similar to those of neurons studied in situ; (c) intrinsic cardiac and intrathoracic extracardiac neurons cultured alone or with cardiomyocytes display a variety of morphologies (unipolar, bipolar, and multipolar), larger and more multipolar neurons being present in cultures derived from stellate versus intrinsic cardiac ganglia; (d) such cultured neurons are associated with a number of neurochemicals, more than one chemical being associated with each neuron. This model presents an excellent opportunity to study the morphology of individual peripheral extracardiac and intracardiac neurons as well as their potential to produce various neurochemicals that are known to be involved in the neuromodulation of cardiomyocyte function.

Animals↗
PubMed1995

Ultrastructure and synaptology of the nucleus ambiguus in the rat: the compact formation.

The fine structure of the esophagomotor compact formation of the nucleus ambiguus was studied. Esophageal motoneurons are atypical in that they have extensive direct somato-somatic and somato-dendritic appositions without intervening glial processes. A unique feature is the presence of finger- and leaf-like somatic protrusions which partially wrap longitudinally oriented dendrites and, occasionally, small groups of dendrites and axons. The neuropil contains many longitudinally oriented, small-diameter dendrites of relatively uniform size (1.1 +/- 0.4 S.D. micrograms in diameter). Motoneuronal somatic profiles have 0-5 synapses per profile which represents a synaptic density of 10.6 synapses per soma. Axodendritic synapses measure 0.5 x 0.7 microgram in the transverse plane and are up to 3.0 micrograms long in the sagittal plane. Many axon terminals contact both a soma and dendrite in close apposition. Most axon terminals (> 90%) contain round vesicles and form asymmetric junctions with somata and dendrites. Axon terminal degeneration after electrolytic lesions and labelling after injection of wheat germ agglutinin-horseradish peroxidase in the nucleus of the tractus solitarius show that afferent connections to the compact formation form axodendritic synapses. The ultrastructure and synaptology of esophageal motoneurons is characterized by the close apposition of somata and dendrites (somatic-dendritic bundling), and the longitudinal orientation of dendrites (dendritic bundling), axons and axon terminals in the neuropil. These features may be important morphological substrates for synchronization and coordination of esophageal motoneuronal activity and esophageal peristalsis.

Afferent Pathways↗
PubMed1995

Monoamines in the parabrachial nucleus of the cardiomyopathic hamster.

The development of dystrophic cardiac muscle is related to increases in sympathetic nervous system activity but little is known regarding possible central neural mechanisms that may be involved in cardiomyopathy. The inbred cardiomyopathic hamster is an animal model for studying the development and mechanisms of necrosis in cardiac muscle which resemble non-vascular myocardial diseases of man. Because monoamines are known to play a major role in central regulation of the cardiovascular system, we compared the distribution and density of tyrosine hydroxylase (TH) and 5-hydroxytryptamine (5-HT) immunostaining in the brains of cardiomyopathic hamsters (strain CHF-146), a related strain (CHF-148) of non-cardiomyopathic albino hamsters, and golden Syrian hamsters for possible differences in neurochemical organization. At the time of sacrifice, the cardiomyopathic hamsters exhibit small, calcified lesions on the surface of the ventricular cardiac muscle (early necrotic phase). Brain sections from each group were processed identically and simultaneously. The results show that there were significant differences among strains in the parabrachial nucleus with respect to the two neurochemicals examined. In golden Syrian and albino hamsters, TH and 5-HT immunoreactive axons were lightly-to-moderately stained in the lateral parabrachial nucleus. In the cardiomyopathic hamster, there were significantly more densely stained TH and 5-HT immunoreactive axons in the lateral parabrachial nucleus, in particular the inner part of the external lateral subnucleus. Because the lateral parabrachial nucleus, including the external lateral subnucleus, is known to be involved in regulation of the cardiovascular system, the differential distribution of TH and 5-HT in the parabrachial nucleus of cardiomyopathic hamsters in comparison to normal hamsters suggests that the parabrachial nucleus could be involved in sympathetic mechanisms related to the development of necrosis in cardiac muscle of the cardiomyopathic hamster.

Animals↗
PubMed1995

Nitric oxide modulates signaling between cultured adult peripheral cardiac neurons and cardiomyocytes.

To determine whether nitric oxide (NO) modifies cardiomyocytes directly or indirectly via peripheral autonomic neurons, the effects of NO were studied in long-term (3-6 wk) cultures of adult guinea pig ventricular myocytes alone as well as in cocultures with adult extracardiac (stellate ganglion) or intrinsic cardiac neurons. NADPH diaphorase was associated histochemically with cultured intrinsic cardiac and, to a lesser extent, stellate ganglion neurons. The beating frequency of ventricular myocytes cocultured with intrinsic cardiac neurons (M-intrinsic) or stellate ganglion neurons (M-stellate) increased by 20-30% (P < 0.001) after administration of the NO donor S-nitroso-N-acetylpenicillamine (SNAP); this effect was abolished by the guanylate cyclase inhibitor LY-83583. The beating frequency of noninnervated myocyte cultures was not affected by SNAP. The precursor of NO, L-arginine, also increased the beating rate (approximately 20%; P < 0.05) of M-intrinsic cocultures, not affecting that of M-stellate cocultures or noninnervated myocyte cultures. Augmentor effects induced by SNAP were no longer elicited in the presence of tetrodotoxin and were unaffected by beta-adrenergic or muscarinic receptor blockade. It is concluded that 1) NO-sensitive neurons are present in stellate and intrinsic cardiac ganglia, and these neurons increase the beating rate of cardiomyocytes in the presence of NO; 2) more NO-synthesizing neurons are present in M-intrinsic than M-stellate cocultures, since L-arginine increased the beating frequency of myocytes significantly only in M-intrinsic cocultures; and 3) the beating rate of noninnervated myocyte cultures is not directly affected by NO.

Animals↗
PubMed1995

Modulation of intrinsic cardiac neuronal activity by nitric oxide donors induces cardiodynamic changes.

Studies were performed to determine 1) whether a specific marker for nitric oxide production is associated with canine intrinsic cardiac neurons, 2) whether the transmembrane properties of these neurons can be altered by nitric oxide donors, 3) whether in situ intrinsic cardiac neurons are sensitive to nitric oxide donors, and 4) whether these neurons are involved in cardiac regulation. Thirty to forty percent of canine intrinsic cardiac neurons were labeled with a selective anatomic marker for nitric oxide production. Nitric oxide donors modified the transmembrane properties of a subpopulation of intrinsic cardiac neurons studied in vitro. The nitric oxide donors nitroglycerine, sodium nitrite, and nitroprusside induced concentration-dependent increases in neuronal activity frequently associated with cardiac augmentation. Similar neuronal responses were elicited by N-methyl-D-aspartate receptor activation as well as when the precursor of nitric oxide, L-arginine, and the exogenous nitric oxide donor, S-nitroso-N-acetylpenicillamine, were administered, indicating that intrinsic cardiac neurons can be modulated by nitric oxide donors. Such neurons apparently are tonically influenced by locally released nitric oxide as local administration of the competitive inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl ester, suppressed their spontaneous activity. These data indicate that a significant population of nitric oxide-sensitive neurons exists in the canine intrinsic cardiac nervous system that are involved in cardiac regulation.

Animals↗
PubMed1994

Gross and microscopic anatomy of the canine intrinsic cardiac nervous system.

BACKGROUND: A three-dimensional description of the distribution and organization of the canine intrinsic cardiac nervous system was developed in order to characterize its full extent physiologically. METHODS: The anatomy of the canine intrinsic cardiac nervous system was investigated in 67 mongrel dogs by means of visualization following methylene blue staining as well as by light and electron microscopic analyses. RESULTS: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were identified in specific locations in epicardial fat and cardiac tissue. Distinct epicardial ganglionated plexuses were consistently observed in four atrial and three ventricular regions, with occasional neurons being located throughout atrial and ventricular tissues. One ganglionated plexus extended from the ventral to dorsal surfaces of the right atrium. Another ganglionated plexus, with three components, was identified in fat on the left atrial ventral surface. A ganglionated plexus was located on the mid-dorsal surface of the two atria, extending ventrally in the interatrial septum. A fourth atrial ganglionated plexus was located at the origin of the inferior vena cava extending to the dorsal caudal surface of the two atria. On the cranial surface of the ventricles a ganglionated plexus that surrounded the aortic root was identified. This plexus extended to the right and left main coronary arteries and origins of the ventral descending and circumflex coronary arteries. Two other ventricular ganglionated plexuses were identified adjacent to the origins of the right and left marginal coronary arteries. Intrinsic cardiac ganglia ranged in size from ones comprising one or a few neurons along the course of a nerve to ones as large as 1 x 3 mm estimated to contain a few hundred neurons. Intrinsic cardiac neuronal somata varied in size and shape, up to 36% containing multiple nucleoli. Electron microscopic examination demonstrated typical autonomic neurons and satellite cells in intrinsic cardiac ganglia. Many of their axon profiles contained large numbers of clear, round, and dense-core vesicles. Asymmetrical axodendritic synapses were common. CONCLUSIONS: The canine intrinsic cardiac nervous system contains a variety of neurons interconnected via plexuses of nerves, the distribution of which is wider than previously assumed.

Animals↗
PubMed1994

Chicken interferon gene: cloning, expression, and analysis.

A gene encoding chicken interferon (ChIFN) was cloned from a cDNA library made from primary chick embryo cells that had been "aged" in vitro so as to produce copious amounts of IFN upon induction. The coding region is predicted to produce a signal peptide of 31 amino acids and a mature protein of 162 amino acids with a molecular weight of 18,957. There are four potential N-glycosylation sites and six cysteine residues. Three disulfide bonds are possible, with two being common to most mammalian type I IFNs. A motif of 10 amino acids surrounding Cys-137 is highly conserved: It shows 80% homology with mammalian type I IFNs, but only 30% with a reported fish IFN. The T-rich 3' UTR displays the canonical element AATAAA required for polyadenylation, and contains six repeats of the octamer CTATTTAT that may be involved in down-regulating translation. Northern blots demonstrate that the accumulation of ChIFN mRNA correlates with induction of ChIFN determined by bioassay. Biologically active protein was synthesized in transfected mouse L cells using mRNA prepared in vitro from the cloned sequence. This activity was neutralized by a monoclonal antibody prepared against purified ChIFN. The ChIFN gene shows sequence identity at the amino acid/nucleotide level with consensus mammalian IFNs as follows: alpha (24/23%), beta (20/24%), omega (23/43%), tau (20/43%), gamma (3/31%), and with flatfish IFN (16/35%). The conserved features of the predicted ChIFN protein and the general similarity of predicted secondary structure suggest a molecule that fits the five alpha-helix three-dimensional topology reported for type I mammalian IFNs.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Differential cardiac responses induced by nicotine sensitive canine atrial and ventricular neurones.

OBJECTIVE: The aim was to study the locations and functions of atrial and ventricular nicotine sensitive neurones. METHODS: In anaesthetised open chest dogs, cardiovascular effects elicited by nicotine (100 micrograms in 0.1 ml 0.9% saline), administered at specific loci of in situ atrial and ventricular ganglionated plexi, were studied before and after decentralisation. RESULTS: Cardiovascular responses were elicited when 41% of atrial and 36% of ventricular ganglionated plexus loci were studied. Subsequently, ganglia were identified adjacent to active sites. When cardiovascular responses were elicited, either tachycardia or bradycardia was induced, depending on the locus investigated. When tachycardia occurred, atrial and/or ventricular forces were augmented. When bradycardia occurred, atrial forces were suppressed. Ventricular fibrillation was induced in two animals when ventricular ganglionated plexus loci were investigated. Cardiovascular responses were not elicited when up to 2000 micrograms of nicotine were administered adjacent to intrinsic cardiac axons, indicating that responses were not primarily due to axonal effects. Control injections of saline (0.1 ml) into active loci did not elicit cardiovascular responses. Following acute decentralisation, responses initiated by nicotine were attenuated or eliminated. Depressor responses were no longer elicited following atropine administration, nor augmentor ones following propranolol administration. CONCLUSIONS: (1) The canine heart contains nicotine sensitive neurones which can induce either augmentor or depressor cardiac effects. (2) Nicotine sensitive atrial neurones modify primarily, but not exclusively, atrial tissues, whereas ventricular ones modify primarily, but not exclusively, ventricular tissues. (3) Nicotine sensitive intrinsic cardiac neurones can interact with central neurones to modulate the heart.

Animals↗
PubMed1993

Cocultures of adult ventricular myocytes with stellate ganglia or intrinsic cardiac neurones from guinea pigs: spontaneous activity and pharmacological properties.

OBJECTIVE: The aim was to develop long term primary cocultures of adult ventricular myocytes with autonomic neurones dissociated from stellate or intrinsic cardiac ganglia. This was to provide an experimental model for the investigation of the regulatory role of autonomic neurones with respect to cardiac myocyte function. METHODS: Ventricular myocytes and stellate and intrinsic cardiac neurones were enzymatically dissociated from adult male guinea pigs and plated together on 13 mm cover slips; the cultures were maintained in an incubator for two to 10 weeks. The electrical properties of cultured myocytes and neurones were investigated by means of a conventional microelectrode technique and the spontaneous contractile activity of the myocytes was recorded by a video system. The electrical, contractile, and pharmacological properties of myocyte-neuronal networks were investigated by superfusing the cultures with various neuromodulators and blockers. RESULTS: The electrical properties of the cultured myocytes and neurones were similar to those reported in other in vitro studies. Innervated and non-innervated cardiomyocyte cultures responded differently, however, to various pharmacological interventions. Spontaneous contractions were attenuated by tetrodotoxin (4 x 10(-7) M), beta adrenergic blockade, and nicotinic blockade more in cocultures than in cardiac myocyte cultures alone. On the other hand, the beta agonist isoproterenol increased the spontaneous beating in both types of cocultures more than in myocytes alone. The effects of the muscarinic agonist bethanechol and the muscarinic blocker atropine were not significantly different in innervated and non-innervated cultures. Nicotine induced either an increase or decrease in contractile rates of both cocultures and did not affect non-innervated myocyte cultures. CONCLUSIONS: Cocultures of myocytes and autonomic neurones alter the responses of myocytes relative to cultures without neurones. The results suggest that functional contacts can be established between adult myocytes and dissociated neurones in primary cultures. Contractile rates of such myocyte cultures are influenced by the presence of neurones. Neurones innervating these cultures were modified by beta adrenergic, muscarinic, and nicotinic agents.

Animals↗
PubMed1992

Electrophysiological properties of in vitro intrinsic cardiac neurons in the pig (Sus scrofa).

Physiological properties and synaptically mediated responses of 34 ganglionated plexus neurons from the right atrium of the pig heart were studied with in vitro intracellular recording techniques. Whole-cell input resistance of these neurons was lower, time constant was shorter, and threshold for directly evoked action potentials was higher than the same properties in extracardiac autonomic neurons. Long intracellular depolarizing current pulses (400-500 ms) failed to generate more than one or two action potentials. Nicotinic and non-nicotinic synapses were present on neurons in cardiac ganglia and neuronal properties could be modified by norepinephrine. Based on their physiological properties, cardiac ganglionated plexus neurons in the pig appear to represent a distinct population of autonomic neurons that may be capable of intracardiac integration of efferent information to the heart.

Animals↗