Parasympathetic ganglia

General types of physiological functions attributed to quaternary ammonium compounds are curare action, muscarinic—nicotinic action, and ganglia blocking action. The active substance of curare is a quaternary that can produce muscular paralysis without affecting the central nervous system or the heart. Muscarinic action is the stimulation of smooth-muscle tissue. Nicotinic action is primary transient stimulation and secondary persistent depression of sympathetic and parasympathetic ganglia. 

Ganglionic nicotinic receptors are found on postsynaptic neurons in both parasympathetic and sympathetic ganglia and in the adrenal gland. Ganglionic nicotinic receptors appear in tissues of neural crest embryonic origin and exhibit identical properties in sympathetic and parasympathetic ganglia. 

Pauly JR, Ullman EA, CoUins AC (1990b) Strain differences in adrenalectomy-induced alterations in nicotine sensitivity in the mouse, Pharmacol Biochem Behav 35 171-179 Pauly JR, Marks MJ, Gross SD, Collins AC (1991) An autoradiographic analysis of cholinergic receptors in mouse brain after chronic nicotine treatment, J Pharmacol Exp Ther 258 1127-1136 Perry DC, KeUar KJ (1995) [ H]epibatidine labels nicotinic receptors in rat brain an autoradiographic study. J Pharmacol Exp Ther 275 1030-1034 Perry WLM, Talesnik J (1953) The role of acetylchoUne in synaptic transmission at parasympathetic ganglia. J Physiol 119 455 69... 

Sympathetic parasympathetic ganglia ACh Nicotine Trimethaphan Ganglionic type (o3p4) Nicotinic (N) cholinoceptor ligandgated cation channel formed by five transmembrane subunits muscular type (al2PlY5)... 

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). 

The airway effects of released acetylcholine are mediated via activation of three distinct muscarinic receptor subtypes Mj, in parasympathetic ganglia, mucous glands and alveolar walls autoinhibitory M2, in parasympathetic nerve terminals and M3, in airway smooth muscle, mucus glands, and airway epithelium. 

The answer is d. (Hardman, pp 192-193.) Nicotine is a depolarizing ganglionic blocking agent that initially stimulates and then blocks nicotinic muscular (NM) (skeletal muscle) and nicotinic neural (NN) (parasympathetic ganglia) cholinergic receptors. Blockade of the sympathetic division of the autonomic nervous system (ANS) results in arteriolar vasodilation, bradycardia, and hypotension. Blockade at the neuromuscu-... 

NN receptors—nicotinic-neural receptors (found in parasympathetic ganglia)... 

Schematic diagram comparing some anatomic and neurotransmitter features of autonomic and somatic motor nerves. Only the primary transmitter substances are shown. Parasympathetic ganglia are not shown because most are in or near the wall of the organ innervated. Cholinergic nerves are shown in blue noradrenergic in red and dopaminergic in green. Note that some sympathetic postganglionic fibers release acetylcholine or dopamine rather than norepinephrine. The adrenal medulla, a modified sympathetic ganglion, receives sympathetic preganglionic fibers and releases epinephrine and norepinephrine into the blood. ACh, acetylcholine D, dopamine Epi, epinephrine M, muscarinic receptors N, nicotinic receptors NE, norepinephrine.

The cholinesterase inhibitors can increase activity in both sympathetic and parasympathetic ganglia supplying the heart and at the acetylcholine receptors on neuroeffector cells (cardiac and vascular smooth muscles) that receive cholinergic innervation. 

Ganglion blockers competitively block nicotinic cholinoceptors on postganglionic neurons in both sympathetic and parasympathetic ganglia. In addition, these drugs may directly block the nicotinic acetylcholine channel, in the same fashion as neuromuscular nicotinic blockers (see Figure 27-6). 

Pesticides derived from natural sources include nicotine, rotenone, and pyrethrum. Nicotine is obtained from the dried leaves of Nicotiana tabacum and N rustica. It is rapidly absorbed from mucosal surfaces the free alkaloid, but not the salt, is readily absorbed from the skin. Nicotine reacts with the acetylcholine receptor of the postsynaptic membrane (sympathetic and parasympathetic ganglia, neuromuscular junction), resulting in depolarization of the membrane. Toxic doses cause stimulation rapidly followed by blockade of transmission. These actions are described in Chapter 7. Treatment is directed toward maintenance of vital signs and suppression of convulsions. 

As in the sympathetic division, parasympathetic preganglionic neurons synapse in the periphery with a postganglionic fiber. This synapse usually takes place in a terminal ganglion that is located directly in the organ or tissue supplied by the postganglionic neuron. Consequently, the parasympathetic ganglia are usually embedded directly in the innervated organ or tissue. 

Summary of the neurotransmitters released and the types of receptors found within the autonomic and somatic nervous systems. [Note This schematic diagram does not show that the parasympathetic ganglia are close to or on the surface of the effector organs and that the postganglionic fibers are usually shorter than the preganglionic fibers.]... 

Muscarinic stimulation leads to activation of K+ channels in sympathetic [128] and parasympathetic ganglia [129,130], as well as in central neurons [131,132]. Similarly, in atrial heart cells, acetylcholine combines with muscarinic receptors and opens a K+ channel [133,134]. Increased K+ causes the cells to hyperpolarize and become less excitable. Secretion is attenuated in neuronal cells and chronotropy is inhibited in atrial cells (for review see Ref. 135). 

As we have seen [in a previous chapter], acetylcholine occurs in s niapses in both the somatic and the autonomic nervous system. The nicotinic acetylcholine receptor is found in the motor endplate of the skeletal muscle, and in both the sympathetic and the parasympathetic ganglia of the peripheral autonomic system. Muscarinic acetylcholine receptors are found at the endings of all secondary neurons within the parasympathetic part of the peripheral autonomous system. In addition, acetylcholine receptors of both types also occur in the brain. Drugs with a useful degree of selectivity for each of these targets are available and used in practical medicine. Selectivity is based on two principles ... 

Once translocated into the cytosol, the toxic fragments exert their paralytic effects by inhibiting ACh release from neuromuscular junctions as well as other peripheral cholinergic sites, including sympathetic and parasympathetic ganglia and post-ganglionic parasympathetic synapses (Lamanna, 1959 Vincenzi, 1967 Simpson, 2004). 

Acetylcholine In Synaptic Transmisalon at Parasympathetic Ganglia. J. Physiol. 119 455-469. 

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