Postganglionic sympathetic nerves

Losulazine (20) is an orally and parenterally active antihypertensive agent apparently acting on peripheral postganglionic sympathetic nerve terminals to deplete norepinephrine. stores. 

The postsynaptic receptors on any given neuron receive information from transmitters released from another neuron. Typically, postsynaptic receptors are located on dendrites or cell bodies of neurons, but may also occur on axons or nerve terminals in the latter case, an axoaxonic synaptic relationship may cause increases or decreases in transmitter release. In contrast, autoreceptors are found on certain neurons and respond to transmitter molecules released from the same neuron. Autoreceptors may be widely distributed on the surface of the neuron. At the nerve terminal, they respond to transmitter molecules released into the synaptic cleft on the cell body, they may respond to transmitter molecules released by dendrites. Functionally, most autoreceptors appear to decrease further transmitter release in a kind of negative feedback loop. Autoreceptors have been identified for all the catecholamines, as well as for several other neurotransmitters. a2-adrenergic receptors are often found on noradrenergic nerve terminals of postganglionic sympathetic nerves, as well as on noradrenergic neurons in the CNS [36], and activation of these receptors decreases further norepinephrine release. Dopamine autoreceptors,... 

Guanethidine and guanadrel deplete norepinephrine from postganglionic sympathetic nerve terminals and inhibit the release of norepinephrine in response to sympathetic nerve stimulation. This reduces cardiac output and peripheral vascular resistance. 

Noradrenaline is the main catecholamine in postganglionic sympathetic nerves and in the central nervous system it is also released from the adrenal gland together with adrenaline. Recently adrenaline has also been shown to be a transmitter in the hypothalamic region of the mammalian brain so, while the terms "noradrenergic" and "adrenergic" are presently used interchangeably, it is anticipated that they will be used with much more precision once the unique functions of adrenaline in the brain have been established. 

It now seems clear that stores of catecholamines in postganglionic sympathetic nerve pre-synaptic vesicles can, for the purposes of the present discussion, be divided into two types ... 

In the sympathetic nervous system there is the possibility to reduce the release of noradrenaline. The alkaloid reserpine is known to interfere with the ability of the postganglionic sympathetic nerves to store noradrenaline. This results in a reduction of the sympathetic tone which is a useful measure in the treatment of essential hypertension. These type of drugs are classified as antisympathotonics. 

Norepinephrine is released from the varicosities of the postganglionic sympathetic nerves during neural activity and interacts with the adrenoceptors of the effector organ, producing the characteristic response of the... 

The adrenergic neuron-blocking drugs are antihypertensive because they prevent the release of transmitters from peripheral postganglionic sympathetic nerves. The contraction of vascular smooth muscle due to sympathetic nerve stimulation is thereby reduced, and blood pressure decreases. Guanethidine is the prototypical member of this class. 

Oral 250, 500 mg tablets Parenteral 50 mg/mL for injection Postganglionic Sympathetic Nerve Terminal Blockers Guanadrel (Hylorel)... 

In 1978 we compared the structure activity requirements for the DA, (vascular DA) receptor with other putative DA receptors (1,4 )7 The limited SAR data available at that time supported the existence of at least two different DA receptors. DA-induced responses were divided into two categories on the basis of differences in agonist activity and potency series. The following phenomena appeared to be due to activation of DA2 receptors inhibition of norepinephrine release from the postganglionic sympathetic nerve inhibition of ganglionic transmission inhibition of prolactin release and emesis. Review of the current literature has not revealed exceptions to these correlations. 

Parasympathetic input to the GI tract is excitatory preganglionic neurons in the vagus innervate the parasympathetic ganglia of the enteric plexuses. Postganglionic sympathetic nerves also synapse with the intramural enteric parasympathetic ganglia. Sympathetic nerve activity induces relaxation primarily by inhibiting the release of ACh from the preganglionic fibers. 

NE (levarterenol, /-noradrenahne) is released by mammalian postganglionic sympathetic nerves (Table 10-1). NE constitutes 10-20% of the catecholamine content of human adrenal medulla and as much as 97% in some pheochromocytomas, which may not express phenylethanolamine-(V-methyltransferase. 

The third mechanism, the ft adrenergic receptor pathway (bottom of Figure 30-2A), is mediated by the release of NE from postganglionic sympathetic nerves activation of ftj receptors on juxtaglomerular cells enhances renin secretion. 

Reserpine and guanethidine are both sympathoplegics that act on the postganglionic sympathetic nerve terminal. Reserpine enters the CNS readily and causes important CNS toxicity. Guanethidine, on the other hand, is too polar to cross the blood-brain barrier easily and is almost devoid of central toxicity. The answer is (D). 

Gut and liver catechol-O-methyltransferase Postganglionic sympathetic nerve terminals Preganglionic S3Tnpathetic nerve terminals Vascular smooth muscle cell receptors A semiconscious patient in the intensive care unit is being artificially ventilated. Random spontaneous respiratory movements are rendering the mechanical ventilation ineffective. A useful dmg to reduce the patient s ineffective spontaneous respiratory activity is (A) Baclofen Dantrolene Pancuronium Pyridostigmine Succinylcholine... 

During activation of postganglionic sympathetic nerves there is an exocytotlc release of norepinephrine which is dependent upon the movement of calcium across the neural cell membrane. The effects of CEB on stimulus-secretion coupling in S3nnpathetlc nerves has been studied in several different preparations. Verapamil does not affect the neural release of norepinephrine in either Isolated cat heart or in the pithed rat. In the latter model nifedipine blunted increases in blood pressure due to activation of sympathetic nerves but did not affect cardiovascular responses to exogenous norepinephrine suggesting a prejunctional site of inhibition. 

Some postganglionic sympathetic nerves (i.e, thermoregululory sweat glands and skeletal muscle vasodilator fibres). 

Human beings react with increased sympathoadrenal activity when they are confronted with challenging events or situations demanding active involvement The secretion in the peripheral blood of the catecholamines adrenaline and noradrenaline are important parts of this reaction. Sympathetic innervation via the splanchtuc nerve stimulates the adrenal medulla. This gland secretes adrenaline and a small fraction of the circulating noradrenaline in the blood. The latter hormone is secreted mainly at the ptesynaptic endplates of the (postganglionic) sympathetic nerve fibers. It has been shown that the ex-... 

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