Roles of cyclic nucleotides in the synaptic transmission in sympathetic ganglia of rabbits

1. Two kinds of slow postsynaptic potentials can be elicitable in the rabbit superior cervical ganglion: a dopaminergic hyperpolarizing (slow IPSP) one and a muscarinic depolarizing (slow EPSP) one, respectively. 2. Cyclic AMP may not be involved in the generation of slow IPSP, whereas it certainly mediates the dopamine-induced enduring modulatory enhancement of the slow EPSP response. 3. Cyclic GMP appears to mediate at least one of the components in the mechanism underlying the slow EPSP by generating a depolarization with no change in membrane conductance. 4. Cyclic GMP does additionally regulate the dopamine for cyclic AMP)-induced modulatory enhancement of the slow EPSP by antagonizing it in a uniquely time-dependent fashion.     

Comparative research on synaptic transmission in the sympathetic ganglia of rabbits and frogs during acetylcholinesterase inhibition

Organophosphorus inhibitor of acetylcholinesterase (AChE) armin (1 x 10(-6) M) induced a variety of pre- and postsynaptic effects resulting from the AChE inhibition and subsequent accumulation of acetylcholine (ACh) in the synaptic cleft. The intensity of postsynaptic effects (level of neuron depolarization, degree of action potential depression) was shown to be different in the ganglia of frog and rabbit. This could be explained by differences in the total amount of ACh released in response to nerve stimulation as well as at rest. Both muscarinic and nicotinic cholinoreceptors were involved in the process of sustained depolarization of the neurons in the rabbit superior cervical ganglion after AChE inhibition. In frog ganglion neurons the nicotinic receptors did not participate in depolarization evidently due to their fast desensitization. The activation of presynaptic muscarinic receptors resulted in decrease of ACh released by nerve stimulation seems to weaken depolarization and blockade of synaptic transmission in sympathetic ganglia treated by AChE inhibitors.     

Relation between the state of the vestibular analyzer in rabbits and their individual radiosensitivity when irradiated with a dose of 150 Gy

The authors have revealed a relationship between the original functional state of the vestibular analyzer of rabbits and their individual radiosensitivity. The coefficient of correlation between the vestibular analyzer sensitivity threshold and the life expectancy after exposure to gamma-rays at a linear accelerator of electrons (7.6 MeV, 150 Gy) was 0.505.     

Somatostatin-like immunoreactivity in human sympathetic ganglia

Summary The localization of somatostatin-like immunore-activity (SOM-LI) was examined in human lumbar sympathetic ganglia using the peroxidase-antiperoxidase method. Few of the principal neurons showed immunolabelling for somatostatin and sparse networks of nerve terminals were unevenly associated with ganglion cells. Using light microscopy, the most intense SOM-LI was seen in the perinuclear zone of the neurons. Electron-microscopically, the staining was localized on the membranes of the Golgi apparatuses. In the nerve terminals, SOM-LI was seen inside the small vesicles (40–60 nm diameter). All neurons with SOM-LI were also found to be tyrosine-hydroxylase immunoreactive when excamined with a double-staining technique. These results provide evidence that somatostatin and noradrenaline co-exist in human sympathetic neurons.     

Portal-like microcirculation in rat sympathetic ganglia

The fine structure of intraganglionic blood vessels of rat superior cervical sympathetic ganglia is studied with the light microscope and with both conventional and ultrastructural histochemical methods. Two sets of small capillaries together with larger sinusoidal ones are identified. One set of capillaries is associated with the clustered (type II) small catecholamine-containing (CC) cells and exhibits features suggestive of fluid transport function (multiple wide fenestrae and active pinocytosis). The second set of capillaries is in direct relation to the sympathetic neurons (SN) and shows characteristics suggestive of absorptive function (microvilli and pinocytotic vesicles). The larger sinusoidal capillaries are observed in the vicinity of type II CC cells, extend parallel to the long axes of the perikarya of the neurons and occasionally form loops around them. The latter are assumed to be larger blood spaces connecting the two capillary sets and serve to slow the circulation around the neurons. A pattern of portal-like intraganglionic microcirculation through which type II CC cells participate in modulating the SN is postulated. Type II CC cells secrete a catecholamine modulator which, driven by concentration gradient, gains access to the circulation through the fenestrated capillaries. The sinusoidal capillaries serve to perfuse the SN with a slow stream of blood rich in the catecholamine modulator. The latter can be filtered through the microvilli and pinocytotic vesicles of the second set of capillaries to induce slow inhibitory postsynaptic potential on the SN.     

Peptidergic synaptic transmission in sympathetic ganglia

Biologically active peptides have been localized in neuronal cell bodies, axons, and synaptic boutons of sympathetic ganglia; some of these peptides may be neurotransmitters. For example, substances immunologically similar to substance P and luteinizing hormone-releasing hormone appear to be released from nerve terminals in sympathetic ganglia. In each case, the postsynaptic action of the peptide lasts for several minutes and is accompanied by a combination of decreases and increases in the membrane conductance that are voltage dependent. These peripheral peptidergic synapses may be models for peptidergic transmission in the central nervous system where detailed analysis is more difficult.     

Amphibian sympathetic ganglia in tissue culture

1. A culture medium has been developed for amphibian sympathetic nervous tissue but it is suggested that the ionic values should be adjusted to correspond to the concentrations of salts in the plasma of particular species. 2. The morphology, monoamine fluorescence, growth and differentiation of sympathetic ganglia of the frog, Limnodynastes dumerili, have been studied in culture. 3. Two types of neuron could be distinguished largely according to size, namely small, 18 X 20 mum and large, 38 X 42 mum. The possibility that these represent one type at different stages in development or represent functionally distinct neurons is discussed. 4. The sympathetic neurons are extremely sensitive to nerve growth factor (NGF) which caused an increase in the size of the cell bodies, the number of nerve fibres regenerating, the rate of axonal growth and synthesis of catecholamines. 5. Various other cell types appearing in the cultures have been described, including chromaffin, satellite, Schwann, multipolar and epithelial cells as well as fibroblasts, melanocytes and macrophages. The epithelial cells show slow contractions and changes in shape.