Neural coordination of excitation of ferret trachealis muscle

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.

The airway-related parasympathetic motoneurones in the ventrolateral medulla of newborn rats were dissociated anatomically and in functional control

The respiratory-related synaptic control of the airway-related preganglionic parasympathetic motoneurones (APPMs) has not been investigated, and whether differently targeted APPMs receive differential respiratory-related synaptic modulation is unknown. In this study, putative APPMs in the ventrolateral medulla of newborn rats were retrogradely traced with fluorescent tracer and were examined using the patch-clamp method in brainstem slices with respiratory rhythm. The results indicate that tracer application directly to the recurrent laryngeal nerve only labelled the putative APPMs within the compact portion of nucleus ambiguus (cNA), while tracer injection into the trachea wall labelled the putative APPMs both in cNA and in the area ventral/ventrolateral to cNA (vNA). The putative APPMs within cNA received mainly inhibitory inputs, which in some (9 of 20) neurones showed an inspiratory-related attenuation and in others (7 of 20) showed an inspiratory-related augmentation. At least some putative APPMs within cNA, of which the inhibitory synaptic inputs showed inspiratory-related changes, might be related to the control of laryngeal muscles. The putative APPMs in vNA receive both excitatory and inhibitory inputs, and central inspiratory activity excited some (11 of 19) neurones via augmentation of their excitatory inputs and inhibited others (8 of 19) via augmentation of their inhibitory inputs. At least some putative APPMs in vNA might be trachea-related motoneurones. These results provide evidence that APPMs controlling different segments of the airway might be dissociated in the ventrolateral medulla both anatomically and in functional control.

Postnatal - physiological research of the bronchial receptor system development on the isolated preparation of the human trachea in vitro

Research was done on pharmacological-physiological development of the bronchial receptor system on the smooth muscles of trachea in the newborn children, alive-born and stillborn children. Monitored was the response on: acetylcholine, dopamine, histamine and serotonin in different molar concentrations 10(-4), 10(-3), 10(-2), 10 mol/dm(-3), micromol/dm(-3)). Research was done on tonus of tracheal smooth muscles of 23 tracheal preparations taken by autopsy after death from different factors. Based on pharmacological-physiological research on the preparations of human isolated trachea it was find out that: acetylcholine stimulation effect is significant (p>0,01) in 38-41 weeks of pregnancy comparing with that in 30-37 weeks of pregnancy (p>0,01), while dopamine stimulation effect is significant (p>0,05) in 30-37 pregnancy weeks comparing with the effect of acetylcholine and dopamine on the still-born infants of the same pregnancy period (p<0,01). Histaminic receptors were developed during intrauterine life after 38 weeks of pregnancy (p>0,025). Serotonin has caused contraction of the bronchial smooth muscles after 30 pregnancy weeks, but response was not significant (p<0,01). This suggests that cholinergic and adrenergic system of the airways in alive newborn infants develops in parallel intrauterine, contrary to other systems which develop in certain extrauterine life phases.

Labeling of vagal motoneurons and central afferents after injection of cholera toxin B into the airway lumen

We tested the hypothesis that application of the subunit B of cholera toxin (CTB) to the airway mucosa would produce labeling of neuronal somata and sensory fibers in the medulla oblongata. Using (125)I-CTB as a tracer, we demonstrated first that CTB is transported across the tracheal epithelium, but once in the airway wall, it remains confined to the subepithelial space and lamina propria. Despite the rarity of intrinsic neurons in these areas, intraluminal CTB labeled approximately 10-60 neurons/rat in the nucleus ambiguus and a smaller number of neurons in the dorsal motor nucleus of the vagus. Well-defined sensory fiber terminals were also labeled in the commissural, medial, and ventrolateral subnuclei of the nucleus of the tractus solitarius. Approximately 50 and 90% of the neurons labeled by intraluminal CTB were also labeled by injections of FluoroGold into the tracheal adventitia and lung parenchyma, respectively. These findings demonstrate that a substantial number of medullary vagal motoneurons innervate targets in the vicinity of the airway epithelium. These neurons do not appear to be segregated anatomically from vagal motoneurons that project to deeper layers of the airway wall or lung parenchyma.

Morphology and electrophysiology of guinea-pig paratracheal neurones

BACKGROUND

Although guinea-pig tracheal preparations are used as models of asthma, the morphological and electrophysiological characteristics of its associated ganglion neurones (paratracheal neurones) have not been characterized.

METHODS

Intracellular staining and electrophysiological recording techniques have been applied to guinea-pig paratracheal neurones in isolated preparations.

RESULTS

Most (32/35) neurones were multipolar, with many short (< 70 microns), finely tapering processes and one or more long processes; the latter, which were traced for up to 400 microns, travelled along the interconnecting nerve trunks, often in pairs, or over smooth muscle bundles. About 20% (6/32) of neurones had conspicuous somal extensions that gave rise to 3-8 processes. The soma morphology of neurones of the intrinsic ganglionated plexus close to the trachealis muscle were usually more complex than those in or associated with recurrent or vagal nerve trunks. Two types of neurone were identified electrophysiologically; neurones with fast excitatory synaptic potentials were found only in ganglia located very close to the smooth muscle, whereas > 90% of neurones lacking synaptic inputs were associated with recurrent nerve trunks. Transmural or focal electrical stimulation failed to evoke either slow inhibitory or slow excitatory (cholinergic or non-cholinergic) synaptic potentials in either electrophysiological type.

CONCLUSIONS

It is tentatively concluded that the neurones of the intrinsic ganglionated plexus receiving synaptic input probably provided the para-sympathetic innervation to effector cells (such as trachealis muscle). Both these and the spiking neurones located in or near nerve trunks showed little potential for synaptic modulation of their excitability.

Effects of some K(+)-channel inhibitors on the electrical behaviour of guinea-pig isolated trachealis and on its responses to spasmogenic drugs

1. A study has been made of the effects of inhibitors selective among plasmalemmal K(+)-channels on the sensitivity and responsiveness of guinea-pig trachealis muscle to carbachol, histamine and KCl. The effects of the K(+)-channel inhibitors on the resting membrane potential and spontaneous electrical activity of the trachealis cells have also been examined. 2. In indomethacin (2.8 microM)-treated trachealis muscle, dofetilide (1 microM) and glibenclamide (10 microM) were each devoid of spasmogenic activity. In contrast, 4-aminopyridine (4-AP, 62.5 microM--8 mM), charybdotoxin (ChTX, 100 nM) and iberiotoxin (IbTX, 100 nM) were each spasmogenic. Spasm evoked by 4-AP, IbTX or ChTX was reduced, though not abolished, by atropine (1 microM). Spasm evoked by 4-AP (1 mM), ChTX (100 nM) or IbTX (100 nM) was unaffected by tetrodotoxin (TTX; 3.1 microM) or by tissue pretreatment with capsaicin (1 microM for 30 min). Spasm evoked by IbTX or ChTX was abolished by nifedipine (1 microM). 3. Dofetilide (1 microM) and glibenclamide (10 microM) were each without effect on the tracheal sensitivity or responsiveness to carbachol, histamine or KCl. 4-AP (1 mM) antagonized carbachol, potentiated histamine but did not affect tissue sensitivity to KCl. When the effects of 4-AP were examined in the presence of atropine (1 microM), it potentiated all the spasmogens including carbachol. IbTX and ChTX (each 100 nM) potentiated all three spasmogens. Potentiation of histamine induced by 4-AP (1 mM) or IbTX (100 nM) was also observed in tissues treated with a combination of atropine (1 microM) and TTX (3.1 microM). 4. Dofetilide (1 and 10 microM) was without effect on the resting membrane potential or spontaneous electrical activity of the trachealis cells. 4-AP (1 mM) evoked depolarization and caused a small increase in the frequency of slow wave discharge. The depolarization evoked by 4-AP was abolished by atropine (1 microM). IbTX (100 nM) and ChTX (100 nM) each evoked little or no change in resting membrane potential but converted the spontaneous slow waves into spike-like, regenerative action potentials. These electrophysiological effects of IbTX and ChTX were unaffected by atropine (1 microM). 5. It is concluded that the dofetilide-sensitive, cardiac, delayed rectifier K(+)-channel is either not expressed in trachealis muscle or is of no functional importance in that tissue. The ATP-sensitive K(+)-channel (KATP) does not moderate tracheal sensitivity to spasmogens such as carbachol, histamine and KCl. The 4-AP-sensitive delayed rectifier K(+)-channel (Kdr) and the large Ca(2+)-dependent K(+)-channel (BKCa) each moderate trachealis muscle sensitivity to spasmogens. Neither Kdr nor BKCa plays an important role in determining the resting membrane potential of guinea-pig trachealis cells. However, the BKCa channel is responsible for limiting the effects of the increase in membrane Ca2+ conductance associated with the depolarizing phase of slow waves. It is BKCa channel opening that prevents the development of a slow wave into a spike-like regenerative action potential.

Noradrenaline depletion in patients with coronary artery disease before and after percutaneous transluminal coronary angioplasty with iodine-123 metaiodobenzylguanidine and single-photon emission tomography

Iodine-123 metaiodobenzylguanidine (MIBG) is a noradrenaline analogue which can be used as a tracer to investigate the cardiac sympathetic nervous system. Regional ischaemia leads to noradrenaline depletion with functional denervation which can be demonstrated by reduced MIBG uptake. In order to evaluate the reversibility of ischaemia-associated damage to the sympathetic nervous system, neuronal scintigraphy with 123I-MIBG and myocardial rest and stress perfusion scintigraphy with technetium-99m sestamibi was performed in 16 patients with coronary artery disease before and 3-4 months after percutaneous transluminal coronary angioplasty (PTCA). Partial re-innervation occurred in five patients, the degree of stenosis of remaining lesions being estimated by repeat angiography to be below 40%. Unchanged MIBG defects could be confirmed in four patients with residual lesions of between 40% and 50%. Increased MIBG defects were shown in three patients with significant restenoses of more than 70%. In all patients the neuronal defects exceeded the ischaemia-induced or scar-associated perfusion defects. Three patients dropped out of this study: one for technical reasons, one due to emergency aortocoronary bypass surgery and one due to diabetic polyneuropathy. This investigation shows that the sympathetic nervous system is highly sensitive to ischaemia. Further studies need to be done to assess the conditions allowing re-innervation after PTCA.

Endogenous tachykinins facilitate transmission through parasympathetic ganglia in guinea-pig trachea

1. Exogenous and endogenous tachykinins facilitate cholinergic nerve-induced bronchoconstriction in guinea-pig. Using a vagally innervated guinea-pig tracheal tube preparation we have investigated the involvement of endogenous capsaicin-sensitive neuropeptides in both pre- and postganglionic cholinergic neurotransmission. The effects of the neutral endopeptidase inhibitor (NEP), phosphoramidon, were investigated in this preparation either alone or in conjunction with sensory neuropeptide depletion by capsaicin pretreatment. The subtype of neurokinin receptor mediating this facilitatory effect of tachykinins has also been examined, by the use of selective tachykinin receptor agonists and a selective NK1 receptor antagonist. 2. Cholinergic contractions of the sealed Krebs filled tracheal tube preparation were recorded as increases in intraluminal pressure and were induced either by (i) pre-ganglionic vagus nerve stimulation (PGS), (ii) stimulation of postganglionic intramural nerves via transmural stimulating electrodes (TMS) in the presence of ganglion-blocking concentrations of hexamethonium and (iii) application of exogenous acetylcholine (ACh). 3. The effect of phosphoramidon, which inhibits the breakdown of tachykinins, was investigated on ACh-, PGS- and TMS-induced contractions. Phosphoramidon (1-10 microM) facilitated contractions of the trachea induced by PGS, in a concentration-dependent manner, but had no effect on contractions of the trachea induced either by TMS or exogenous ACh. 4. The facilitatory effect of phosphoramidon (10 microM) on PGS-induced contractions was abolished by pretreating guinea-pigs with capsaicin 7 +/- 2 days before the in vitro experiments. Capsaicin pretreatment did not significantly alter responses to the spasmogens, ACh or substance P. Depletion of sensory neuropeptides, by capsaicin pretreatment was confirmed by the lack of response to capsaicin (1 microM) in vitro. 5. The facilitatory effect of phosphoramidon (10 microM) on PGS-induced contractions was inhibited by the selective NK1 receptor antagonist, GR71251 (1 microM). When applied to the tissues during nerve stimulation,GR71251 caused a small, but significant, inhibition of PGS-induced contractions during low frequency stimulation. No significant effect of GR71251 on TMS-induced contractions was seen at any frequency. There was no significant effect of the NK1 receptor antagonist on contractions of the trachea induced by exogenous ACh.6. The selective NK1 receptor agonist, GR73632 facilitated contractions of the trachea induced by stimulation of both pre- and postganglionic cholinergic nerves, in a concentration-dependent manner, at concentrations that had no significant effect on basal tone (0.01-0.3 nM). The facilitatory effect ofGR73632 on both PGS- and TMS-induced contractions was antagonized by GR71251 (1 microM). In contrast, neurokinin A (1 - 10 nM), which preferentially stimulates NK2 receptors, facilitated contractions induced by both PGS and TMS, and caused a significant increase in basal tone of the trachea. The selective NK3 receptor agonist, senktide (30-300 mM), had no significant effect on nerve-induced contractions or basal tone of the trachea.7. These results suggest that there is release of endogenous tachykinins during vagus nerve stimulation,which can be depleted by capsaicin pretreatment and, which facilitate cholinergic nerve-induced contractions at the level of the parasympathetic ganglia. Facilitatory tachykinin receptors on the postganglionic nerve terminals can be demonstrated by exogenous agonists but do not appear to be activated by endogenous tachykinins under the stimulation conditions of these studies. These data suggest that NK1,receptors may be involved in mediating this facilitatory response to tachykinins but do not exclude an involvement of NK2 receptors. It appears unlikely, however, that NK3 receptors are involved.

Significance of cardiac innervation on spontaneous ventricular arrhythmias elicited by left stellate ganglion stimulation in dogs 4 days after myocardial infarction: comparison of two experimental models

The effects of cardiac sympathetic overactivity on spontaneous arrhythmias and transmural left ventricular effective refractory period (LVERP) were assessed by left stellate stimulation (LSS) in 16 anesthetized dogs. The experiments were performed 4 days after proximal occlusion of the left anterior descending (LAD) coronary artery produced by either ligation (9 dogs) or embolization with histoacryl (7 dogs). The innervation of left ventricular myocardium was studied by light and electron microscopies. Synaptophysin (SYN)- and neuropeptide Y (NPY)-immunoreactive nerve fibers and terminals were thereby detected. In dogs subjected to ligation, LSS elicited negligible arrhythmias in spite of a decrease in LVERP by 6.9 +/- 2.2% (mean +/- SD, p < 0.001). However, dogs with intravascular occlusion were more susceptible to LSS, as indicated by development of sustained ventricular rhythms. In these animals, the LVERP decreased with LSS by 14.6 +/- 3.4% (p < 0.001). The innervation of the anterior left ventricular wall distal to the place of occlusion revealed a higher reduction of SYN- and NPY-immunoreactive nerves in infarcted myocardium and a more heterogeneous distribution of nerves in undamaged regions after ligation, compared to intravascular occlusion. Ultrastructurally, nerve terminals containing small agranular and large dense-core vesicles were found innervating ischemically damaged myocardiocytes. Our findings indicate a higher preservation of nerves in infarcted and noninfarcted myocardium of animals subjected to embolic occlusion of the LAD. Because LSS apparently elicited more arrhythmias in these animals, we suggested a proarrhythmic effect of intact myocardial innervation after infarction.

Multiple motor pathways to single smooth muscle cells in the ferret trachea

1. We investigated the distribution and characteristics of motor pathways to individual smooth muscle cells activated by electrical stimulation of either, single nerves which enter the tracheal plexus (inlet nerves), or a longitudinal nerve trunk (LNT) located near the entrance of an inlet nerve into the plexus. Excitatory junction potentials (EJPs) were recorded using intracellular microelectrodes as an index of smooth muscle cell activation. In all experiments EJPs were completely blocked by tetrodotoxin and by atropine. 2. In smooth muscle fields located in the caudal direction from the point of inlet or LNT nerve stimulation, neural input decreased as a function of distance. There was evidence of a demarcated area innervated by neurons entering the plexus in one inlet nerve. In smooth muscle fields located in the rostral or transverse direction from the site of nerve stimulation, no such demarcated area could be identified. 3. Of the smooth muscle cells located within the innervated fields studied, 83-95% were activated following stimulation of a single inlet nerve or LNT. Evoked EJPs were similar in different innervated cells or units of electrically coupled cells located within the same 1 mm2 'field'. 4. There was overlapping cholinergic motor input to single smooth muscle cells originating from neurons present in different inlet nerves or different neurons present in the same inlet nerve or region of the LNT. Multiple small step increases in the voltage used to stimulate a LNT resulted in three or four step increases in EJP amplitudes. This gives a minimal value for the number of motor pathways that can be activated by neurons in a region of LNT leading to a single smooth muscle cell. 5. Motor pathways to smooth muscle cells located in caudal and rostral fields ran initially in the LNT and exited in proximity to the smooth muscle cell studied. 6. Motor pathways used in transmitting signals to smooth muscle cells to different areas of trachealis muscle varied in their sensitivity to hexamethonium or curare. EJPs evoked in fields located in the caudal direction from the stimulating electrode were abolished by these drugs. Muscle cells located in different rostral fields showed EJPs that were either sensitive or resistant to these drugs. 7. The rostral hexamethonium-resistant pathway ran initially in the LNT but it exited from the LNT several millimetres before reaching the level of the smooth muscle field innervated. This pathway followed stimulation frequencies up to 25 Hz. The final neuron in this pathway released acetylcholine and evoked EJPs were entirely inhibited by atropine.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitrous oxide does not worsen myocardial ischaemia following beta-receptor blockade in isoflurane anaesthetized dogs

The effect of nitrous oxide (N2O) on ischaemic myocardium was investigated in the presence of beta-receptor blockade. Three anaesthetics were compared in each of six dogs: isoflurane 1.8% alone, isoflurane 1.4% with 50% N2O, and isoflurane 1.8% with 50% N2O. Heart rate (HR), systolic aortic blood pressure (SBP), and left atrial pressure (LAP) were held constant during the three treatments. The left anterior descending coronary artery (LAD) was cannulated and perfused with an autoperfusion circuit. Systolic segment length was measured with a sonomicrometer in the LAD and circumflex regions. Regional myocardial blood flow was measured using radioactive microspheres. Propranolol was administered intravenously and then measurements were made during imposition of a stenosis on the perfusion circuit sufficient to decrease systolic shortening by 30%. The substitution of 50% N2O for 0.4% isoflurane had no effect on systolic shortening or transmural myocardial blood flow in the ischaemic or normal region. When N2O was added to 1.8% isoflurane, systolic shortening decreased by 34.6% in the ischaemic and 57.3% in the normally perfused region, while transmural myocardial blood flow distribution did not change significantly. The decrease in shortening was therefore not due to increased ischaemia. These results were similar to those of a previous experiment which was identical except that beta-blockade was absent. It is concluded that beta-receptor blockade does not markedly alter the response of normal or ischaemic myocardium to N2O.

No impairment of sympathetic neurotransmission in stunned myocardium

Reversibly injured myocardium after short periods of ischemia is characterized by a prolonged depression of contractile function which can, however, be enhanced by inotropic interventions. Thus, a lack of inotropic stimulation due to ischemic damage of cardiac sympathetic nerves has been suggested as a mechanism underlying postischemic myocardial dysfunction. We tested this hypothesis in nine anesthetized, vagotomized dogs with left cardiac sympathetic nerve stimulation (CSNS) at 1, 2, 5, 10, and 20 Hz and compared this response to that of intravenous norepinephrine infusion (NE, 0.5-1 microgram/kg.min). Regional myocardial wall thickness was measured using sonomicrometry, and mean systolic wall thickening velocity (MSTV) was determined. CSNS was performed before and at 0, 1, 2, 3, 4, 8, 12, 16, 20, and 24 h after release of a 15 min occlusion of a left circumflex coronary artery branch. Before coronary artery occlusion MSTV was increased in a frequency-dependent way from 7.5 +/- 2.7 (S.D.) (rest) to 8.1 +/- 3.1 (1 Hz), 9.4 +/- 3.2 (2 Hz), 11.4 +/- 2.7 (5 Hz), 13.4 +/- 2.4 (10 Hz), and 16.8 +/- 2.1 (20 Hz) by CSNS, and to 12.6 +/- 3.4 mm/s by NE. Immediately upon reperfusion CSNS increased MSTV from 2.9 +/- 2.0 to 2.9 +/- 2.8, 4.1 +/- 3.0, 5.4 +/- 4.6, 6.9 +/- 4.5 and 9.4 +/- 5.9, and NE increased MSTV to 7.8 +/- 1.9 mm/s. Baseline function recovered over 24 h, as did the response to CSNS and NE. Since the recovery of baseline function paralleled the increases in regional contractile function achieved by CSNS or NE, we conclude that there is no impairment of sympathetic neurotransmission in the stunned myocardium.

Autoradiographic visualization of muscarinic receptors on rat paratracheal neurons in dissociated cell culture

An autoradiographic method was used to determine the distribution of muscarinic receptors on cells cultured from the trachealis muscle of 12-13-day-old rats. Cells identified in these culture preparations included neurones, fibroblasts, smooth muscle, and glial and epithelial cells. The cultured cells were incubated with the specific, irreversible ligand [3H]propylbenzylylcholine mustard, and the autoradiographs generated showed that most, if not all, of the paratracheal neurones observed in these cultures were specifically labelled. Both the neuronal cell body and associated neurites were evenly labelled over their entire surface. Neither the pattern nor the density of neuronal labelling appeared to be influenced by close association with other cultured cell types. Autoradiographic grains for muscarinic receptors also appeared to be uniformly distributed over smooth muscle cells and epithelial cell groups in culture. In contrast, no specific labelling was associated with cultured fibroblasts, glial cells and other non-neuronal supporting cells. The precise localization of muscarinic receptors on different cell types in culture may prove to be useful knowledge in the design of an effective and specific antimuscarinic bronchodilator.

The role of alpha 1- and alpha 2-adrenoceptors in the coronary vasoconstrictor responses to neuronally released and exogenous noradrenaline in the dog

1. Coronary vasoconstriction was examined in response to the neuronal release of noradrenaline produced by bilateral carotid occlusion and the infusion of tyramine (5-50 micrograms/kg/min i.v.) in anaesthetized dogs which had been vagotomized and treated with the beta-adrenoceptor antagonist propranolol (1.0 mg/kg i.v.). These responses were compared to those produced by the infusion of noradrenaline (0.1-0.5 micrograms/kg/min i.v.). 2. Similar increases in late diastolic coronary resistance were produced by bilateral carotid occlusion (0.70 +/- 0.25 mm Hg min/ml), and intravenous infusions of tyramine, 20 micrograms/kg/min (0.70 +/- 0.12 mm Hg min/ml) and noradrenaline, 0.5 micrograms/kg/min (0.59 +/- 0.11 mm Hg min/ml). 3. Selective antagonism at alpha 1-adrenoceptors with prazosin (0.5 mg/kg i.v.) attenuated the coronary constrictor response to bilateral carotid occlusion (0.36 +/- 0.09 mm Hg min/ml), tyramine (0.12 +/- 0.06 mm Hg min/ml) and noradrenaline (0.18 +/- 0.07 mm Hg min/ml). Antagonism at alpha 2-adrenoceptors with idazoxan (1 mg/kg i.v.) attenuated the coronary vasoconstriction produced by bilateral carotid occlusion (0.30 +/- 0.06 mm Hg min/ml), tyramine (0.17 +/- 0.08 mm Hg min/ml) and noradrenaline (0.12 +/- 0.03 mm Hg min/ml). Combined antagonism at both alpha 1- and alpha 2-adrenoceptors with prazosin and idazoxan abolished the responses to bilateral carotid occlusion, tyramine and noradrenaline. 4. These results show that coronary vasoconstriction produced by either neuronally released or exogenous noradrenaline is mediated by both alpha 1- and alpha 2-adrenoceptors. It appears that in the coronary resistance vessels of the dog postjunctional alpha 1- and alpha 2-adrenoceptors are both innervated by sympathetic nerves.

Morphological features of spiking and nonspiking cells in the paratracheal ganglion of the ferret

The present series of experiments was designed to study details of the morphology and connectivity of functionally identified cells located in the paratracheal ganglia of the ferret. The morphology of 11 spiking (AH cells) and seven nonspiking (type B cells) ganglion cells was examined. Intra-axonally injected horseradish peroxidase (HRP) was used as the label. Each spiking and nonspiking cell was identified by intracellular recording prior to the HRP injection. "Whole mount preparations" were processed for HRP histochemistry with diaminobenzidine as the chromogen. HRP-labeled cell bodies of both the spiking AH and nonspiking type B neurons demonstrated similar morphological features. Both types of ganglion cells showed axons arising from a small, ill-defined axon hillock which exited from the cell as single or multiple branches of equal diameter and coursed unidirectionally through the interganglionic nerve trunk to an adjacent ganglion; short, fine, tapering processes (presumptive dendrites) in the immediate vicinity of the injected cell; and processes extending out of the ganglion cell perpendicular to the interganglionic nerve trunk which could be followed into the smooth muscle. Extraperikaryal injections of HRP into a ganglion retrogradely labeled perikarya in the adjacent ganglia. These results demonstrate that in airway ganglia the morphology of spiking and nonspiking neurons is remarkably similar despite electrophysiological differences. In addition it appears that ganglion cells project to adjacent ganglia and to smooth muscle by means of independent axonal processes. These morphological features of the ganglion cells in airways and the trajectories of their axons correspond to known features of their physiology: i.e., the axon of a ganglion cell travels unidirectionally toward the adjacent ganglion and arborizes there, providing anatomical evidence of communication between ganglia via the interganglionic nerve trunk; and the spiking and nonspiking neurons possess similar morphological features that are typical of ganglion cells described in other systems, such as in the myenteric plexus.

Electrophysiology of neuroeffector transmission in the isolated, innervated trachea of the guinea-pig

Intracellular recordings were made from cells of the guinea-pig trachealis muscle. Some cells were electrically quiescent while others exhibited spontaneous slow waves. In quiescent cells, stimulation of the cervical vagus nerve evoked transient depolarization. Occasionally there was a single depolarization, but more often there were several fluctuations in potential. In spontaneously active cells, vagal stimulation induced a transient increase in amplitude of the slow waves without affecting their frequency. Depolarizing responses could be obtained with a single pulse applied to the vagus nerve, and responses increased in amplitude with number of pulses (up to 16 pulses), and with frequency of stimulation (up to 20 Hz). Depolarization did not give rise to spike discharge. Responses to vagal stimulation were blocked by atropine. In the presence of neostigmine, vagally-mediated depolarization was augmented and abortive spikes were observed in a number of cells. In quiescent cells, repetitive stimulation of the sympathetic stellate ganglion evoked slight hyperpolarization. In spontaneously active cells, sympathetic stimulation evoked attenuation, or temporary cessation of slow wave discharge, with or without hyperpolarization. Sympathetic-induced hyperpolarization and suppression of slow waves were both blocked by propranolol, but unaffected by phentolamine. Electrical changes associated with sympathetic stimulation may be of minor importance in the initiation of relaxation.

The architecture of nerves and ganglia of the ferret trachea as revealed by acetylcholinesterase histochemistry

The goal of this study was to determine the architecture of the nerves and ganglia of the ferret trachea. Tracheas from four newborn ferrets and three adult ferrets were stained histochemically for acetylcholinesterase activity and analyzed in their entirety as whole mounts. The architecture consisted of one or two longitudinal nerve trunks overlying the posterior surface of the trachealis muscle, a dense plexus of nerves superficial to the trachealis muscle that interconnected these longitudinal nerve trunks, and, on the anterior surface, a plexus superficial to the submucosal glands and located between the cartilaginous rings. In addition, deep neural plexuses were associated with the trachealis muscle and with the submucosal glands. Ganglion cell bodies along the longitudinal nerve trunks were large (mean diameter +/- S.E. = 34.3 +/- 0.3 microns), were usually attached to the nerve trunk by a stalk, and were loosely clustered in groups of as many 38 cell bodies. By contrast, those cell bodies of the superficial muscle and gland plexuses were significantly smaller (mean diameter +/- S.E. = 24.2 +/- 0.3 microns), were never attached by a stalk, and were tightly clustered in ganglia of one to four cell bodies. We conclude that nerves and ganglia of the ferret trachea constitute one or two longitudinal nerve trunks containing ganglia with large cell bodies, two superficial nerve plexuses containing ganglia with small cell bodies overlying the smooth muscle and submucosal glands, respectively, and two deep nerve plexuses providing the terminal innervation to the muscle and glands.

Effects of angiotensin and ergonovine on large and small coronary arteries in the intact dog

Angiotensin (ATN) and ergonovine (ERG) are known to cause vasoconstriction of the coronary bed. However, ATN effects have been described mainly on the coronary resistance vessels, while ERG effects have been described on proximal conductance vessels. Recent studies have shown that proximal and distal coronary arteries are regulated independently. To examine both proximal and distal effects of ATN and ERG on the same heart, we studied 7 intact dogs, anesthetized with Innovar (Fentanyl 0.4 mg, Droperidol 20 mg, in 1 ml) and nitrous oxide, which were subjected to direct left anterior (LAD) coronary infusion of angiotensin (0.1, 0.5 and 5 micrograms/min) and ergonovine (0.5, 5, and 25 micrograms/min). Using a quantitative angiographic technique to measure artery dimensions and microspheres to measure flow, ERG infusion showed significant large artery constriction at all doses (maximum: 38.9 +/- 7.8% area reduction), and a significant decrease in LAD coronary artery flow, while endocardial/epicardial flow ratio remained unchanged. ATN produced a biphasic effect on the large coronary arteries. The lowest dose produced constriction (12.3 +/- 3.7% area reduction), which returned toward control value with the 0.5 micrograms/min dose (6.0 +/- 1.0% area reduction), and the 5 micrograms/min dose (1.5 +/- 9.5% area reduction), and no significant changes were observed in LAD flow with ATN infusion. Endocardial/epicardial ratio was unchanged, but aortic pressure was significantly increased during 0.5 and 5 micrograms/min ATN infusion. Coronary resistance (pressure/flow) increased with both ERG and ATN. ERG and ATN produce large and small coronary artery constriction. The coronary response to ERG in dogs is similar to the human coronary response, even though previous data indicated a minimal constrictor response to ERG in canine coronary arteries.

Adrenergic innervation of coronary arteries and ventricular myocardium in the pig: fluorescence microscopic appearance in the normal state and after ischemia

A fluorescence histochemical study was performed to describe the adrenergic innervation of the coronary arteries and the left ventricular myocardium in the pig. Large bundles of adrenergic nerve fibres were almost exclusively found running along the large coronary arteries. The arteries usually show a dense innervation of the vessel wall, evenly distributed throughout the adventitia in the larger arteries and more concentrated to the adventitia-medial border in the smaller arteries and arterioles. Most parts of the left ventricular myocardium showed a dense adrenergic innervation, however, a moderate dense and in some areas even sparse innervation was observed towards the apex of the left ventricle. Following 10 or 20 min of ischemia a small reduction in fluorescence intensity was observed in 2 out of 6 hearts. In 4 of the hearts other changes of the appearance of the adrenergic terminals were found, e.g., an unsharp, spread-out or interrupted appearance.

The anatomy of the ferret paratracheal parasympathetic nerve-ganglion plexus

Silver-impregnated preparations of the ferret paratracheal nerve-ganglion plexus were studied for description and quantitation of the general morphology of ganglia and nerve bundles and trunks. Most ganglia were found in one or two chains, separated by interganglionic nerve trunks, running the length of the trachea in close apposition to the trachealis muscle. Ganglia were flat, one cell deep, and characterized by irregular spacing and small and variable numbers of perikarya. Perifascicular, infrafascicular, and mixed types of ganglia were seen. The mean perikaryon density was 127 +/- 20/cm2 of trachealis muscle. In addition to connections to the interganglionic nerve trunk, more than 70% of ganglia were also apparently "connected" to nerve bundles running to the periphery and/or the center of the preparation, and the plexus seemed considerably more complex than originally described. There was no significant change in density, size or type, or connections of ganglia with nerve bundles in the cervical or thoracic trachea.