Conducting pathways of the dog solar plexus

Conducting pathways of the dog solar plexus were studied by recording action potentials from its nerves. The splanchnic nerves are composed of two groups of fast-conducting afferent A fibers (with conduction velocities of 12–15 and 25–56 m/sec), slowly conducting afferent C fibers (0.4–2.0 m/sec), and preganglionic B and C fibers (1.0–12.0 m/sec). Afferent A and C fibers from peripheral nerves run without interruption through the ganglia of the solar plexus, splanchnic nerves, and sympathetic chain and they enter the spinal cord in the composition of the dorsal roots. Cell bodies of A fibers are located in the spinal ganglia, those of the C fibers below the ganglia of the solar plexus, evidently in the walls of the internal organs. Peripheral nerves contain A fibers only with very low conduction velocities (13–20 m/sec) and no fast-conducting A fibers (25–56 m/sec) were found. Preganglionic fibers terminate synaptically on neurons of the ganglia of the solar plexus whose axons run in the peripheral nerves to the internal organs. Synaptic pathways run from some peripheral nerves of the solar plexus into others through its ganglia; in all probability these pathways participate in peripheral reflex arcs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 76–83, January–February, 1976.     

Neuronal activity recorded extracellularly from in situ canine mediastinal ganglia

Spontaneous activity of 226 neurons was recorded from in situ mediastinal ganglia in 10 dogs. Forty-two percent of these were active during specific phases of the cardiac cycle, primarily during systole. Cardiovascular-related activity occurred when systolic pressure was between approximately 70 and 185 mmHg (1 mmHg = 133.3 Pa) whether the pressure was altered by positive inotropic pharmacological agents or cross clamping of the aorta. Twenty percent of the identified neurons displayed respiratory-related activity which occurred during positive pressure inflation or deflation. Thirty-eight percent of the identified neurons displayed bursts of activity or sporadic activity. The activity of 17% of the identified neurons was altered by gentle mechanical distortion of localized regions of the neck, left elbow, ventral thoracic wall, ventral abdominal wall, superior vena cava, right ventricle, or aorta. In the majority of instances cardiovascular- or respiratory-related activity persisted following acute decentralization, indicating that neurons in mediastinal ganglia can function in the absence of influences of central nervous system neurons. Five percent of the identified neurons were activated by single 1-4 ms, 10-20 V stimuli delivered at 0.5 Hz to the nerves connected with either the cranial or the caudal poles of the mediastinal ganglion or the ansae. These neurons were activated after a fixed latency when 0.5 Hz was used and in most instances when 10 Hz was used. These data indicate that 5% or less of the neurons identified projected axons out of the mediastinal ganglia investigated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructure of celiac plexus nodes in the dog

A normal structure of the celiac plexus nodes has been studied in 12 mature dogs. As demonstrate the results of the investigation, gangliocytes of the celiac plexus are characterized with a well developed granular cytoplasmic reticulum and a large number of Golgi complexes. In perikaryon of the gangliocytes, an essential number of mitochondria, microtubules, free ribosomes and polysomes, lysosomes, multivesicular bodies, agranular and granular vesicles and neurofilaments are found. The gangliocyte has one nucleus which occupies about 1/3 of the whole area of the cell. The nucleus is rich in chromatin. The nucleolus makes about 1/5 of the whole area of the nucleus and is intensively rich in heterochromatin. In the celiac plexus nodes amyelinated neural fibers predominate. Dendrites in the gangliocytes differ from axons by a higher electron density of their matrix and contain the same organells that does the perikaryon of the gangliocyte. Rather complex glyoneuronal interrelations are observed in the canine celiac plexus nodes. Synapses are revealed in all ganglionar zones. The axodendritic synaptic contacts predominate over the axosomatic ones.     

Synaptoarchitectonics of the ganglia of the celiac plexus in white rats

In 50 intact white rats at the age of 6, 15, 23 and 30 months synapsoarchitectonics of the celiac plexus nodes was studied by an electron microscopy method. Peculiarities in synapsoarchitectonics are stipulated by pericaryon processes in neurons, some of them have no contacts with the axonal terminals, while others have contacts with the axonal terminals. The former include small (about 0.5 mkm) drop-like and large (up to 1.5 mkm) polymorphous processes within the limits of perisomatic membrane, as well as processes penetrating the neuronal capsule. All of them contain, in different combinations, vesicles, ribosomas, fibrillae, and the largest processes--small cisterns of granular cytoplasmatic network and single mitochondria. The processes of the first group are considered as original stages for the development of the second group processes. The latter are represented by different in size (about 1.0--2.0 mkm) in form (digital, cone-, pin-, goblet-shaped, cylindrical, branching) and in content formations. There is, as a rule, one contact on the processes of an uncomplicated form, while on the branching processes there can be up to three and more contacting axonal terminals. Peculiar features in the composition of the processes taken as a whole (specific forms, absence of dendritic tubes, sometimes numerous contacts with axonal terminals in spite of small size) distinguish them from newly forming dendritic processes and these formations are considered as independent specialized receptor apparatus in the pericaryon of neurons of the celiac plexus.     

Neuronal activity recorded extracellularly in chronically decentralized in situ canine middle cervical ganglia

In chronically decentralized in situ middle cervical ganglia of 10 dogs, 279 spontaneously active neurons were identified. One hundred and ten (39%) of these were spontaneously active during specific phases of the cardiac cycle, primarily during systole, and the activity of nearly half of these cardiovascular-related neurons was modified by gentle mechanical distortion of the vena cavae, heart, or thoracic aorta. Another 60 (22%) of the identified neurons had respiratory--related activity, but the activity of only 2 of them was modified by gentle mechanical distortion of pulmonary tissue. Twenty-nine of the other 109 identified neurons were activated by gentle mechanical distortion of localized regions of the neck, ventral thoracic wall, or ventral abdominal wall. Because of the presence of activity in the chronically decentralized middle cervical ganglion, these data infer that some afferent neurons are located in the thoracic autonomic nervous system. Some middle cervical ganglion neurons were activated by single 1-4 ms stimuli delivered to a nerve connected to the ganglion. During repetitive stimuli delivered at 0.5 Hz none were activated after a fixed latency following the stimuli. Many more neurons were activated by 10- to 200-ms trains of 1-4 ms stimuli delivered with interstimulus intervals of 1-10 ms. The majority of these neurons could still be activated electrically after the administration of cholinergic and adrenergic pharmacological blocking agents.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synaptic transmission in thoracic autonomic ganglia of the dog

Afferent stimulation of one canine thoracic cardiopulmonary nerve can generate compound action potentials in another ipsilateral cardiopulmonary nerve. These compound action potentials persist after acute decentralization of the middle cervical ganglion, indicating that they result from neural activity in the middle cervical ganglion and thoracic nerves. Changing the frequency of stimulation can alter the compound action potentials, suggesting that temporal facilitation or inhibition occurs in this middle cervical ganglion preparation. The compound action potentials can be modified by stimulation of sympathetic preganglionic fibers and by hexamethonium, atropine, phentolamine, propranolol, and (or) manganese. It thus appears that afferent cardiopulmonary nerves can activate efferent cardiopulmonary nerves via synaptic mechanisms in the stellate and middle cervical ganglia. It also appears that these mechanisms involve adrenergic and cholinergic receptors and are influenced by preganglionic sympathetic fibers arising from the cord.