Neurotransmission ganglionic

Ganglionic blocking agent. A drug that blocks neurotransmission at the nicotinic receptors of the sympathetic ganglia, thus blocking vascular reflexes. 

Cholinergic neurotransmission ChEs terminate cholinergic transmission in the central nervous system (CNS), in NMJs and in the autonomic system (the parasympathetic system, somatic motor nerves and pre-ganglionic sympathetic nerves). A few sensory cells and the NMJ in nematodes also include ChEs. 

Fig. 1. Schematic drawing of the cholinergic neurotransmission. In case of ganglionic and neuro-muscular synapses, the receptor is of the nicotinic, sodium channel-coupled type, in case of synapses at the parasympathetic target organs, the receptor is of the muscarinic, G-protein-coupled type. The predominant ehinination pathway of the transmitter acetylcholine...

Like in the neuromuscular junction the neurotransmission can be inhibited either by receptor blockade (non-depolarizing) or by overstimulation (depolarizing) of the receptors. The alkaloid nicotine, in low doses, stimulates ganglia and the adrenaline release from the adrenal medulla. High doses lead to a continuous depolarization of the postsynaptic membrane and thereby to an inactivation of the neurotransmission. All ganglion blockers in clinical use were synthetic amines of the nondepolarizing type trimethaphan, hexamethonium and mecamylamide. 

Like in the parasympathetic and ganglionic neurotransmission, the eliminating enzyme acetylcholine esterase is present at the postsynaptical membrane where it very efficiently reduces the free concentration of the transmitter. 

Transmission through autonomic ganglia is more complex than neurotransmission at the neuromuscular and postganglionic neuroeffector junctions and is subject to numerous pharmacological and physiological influences. In some ganglionic synapses, especially at parasympathetic ganglia, there is a simple presynaptic to postsynaptic cell relationship in others, the presynaptic to postsynaptic cell relationship may involve neurons interposed between the presynaptic and postsynaptic elements (interneurons). 

Neurotransmission at both cholinergic and adrenergic synapses can be influenced by a variety of naturally occurring and synthetic drugs (Table 38.2). For example, ACh secretion is drastically reduced in the presence of botulinum toxin which contains proteases that cleave proteins vital to the process of exocytosis. Nicotine, one of the active ingredients in tobacco can mimic the effects of ACh and increase (or decrease at high doses) autonomic ganglionic transmission as well as that at the... 

Answer D. The pharmacologic action common to both morphine and D-tubocurarine is the release of histamine from mast cells, causing vasodilation. Morphine increases, but D-tubocurarine (via ganglion blockade) decreases, bladder tone. When used in combination with inhalational anesthetics (e.g., halothane), D-tubocurarine has been implicated in malignant hyperthermia. Morphine relaxes the uterus, but D-tubocurarine has no effects on smooth muscle neurotransmission. 

Two distinct factors have been isolated from muscle and spinal cord which clearly promote motoneuron survival and there is synergy between these factors (Dohrmann et al., 1987). Naturally occurring cell death is enhanced in sympathetic and parasympathetic ganglia after blockade of ganglionic neurotransmission with pem-pidine (Hendry, 1973 Maderdrut et al., 1988). On the other hand blockade of activity of the target with curare leads to an increase in survival of mo-... 

Ganglionic blockers block impulse transmission at the sympathetic ganglia. Neurotransmission within the sympathetic and parasympathetic ganglia ... 

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