Cyclic nucleotides nervous system

P2Y receptors are activated by adenine and uridine nucleotides. Most of the known P2Y receptors have been detected in the nervous system [21]. The majority of P2Y receptors inhibit neuronal N-type Ca2+ channels and M-type K+ channels. P2Y1 receptors are found exclusively on platelets, on their precursor megakaryocyte cells and on certain other cultured hematopoietic cells, such as K562 leukemia cells. They can be distinguished from other P2 receptors in that ADP is the most potent natural agonist and ATP is a competitive antagonist. ADP acts via a G protein to inhibit cyclic AMP accumulation, mobilize intracellular Ca2+ and stimulate granule secretion. ADP... 

G PROTEINS 335 PHOSPHOINOSITIDES 347 CYCLIC NUCLEOTIDES IN THE NERVOUS SYSTEM 361... 

Although tremendous progress has been made in characterizing the enzymes that control the synthesis and metabolism of cyclic nucleotides in the nervous system, our understanding of the regulation and interaction of these systems is far from complete. Work is now needed to definitively characterize, for each of these enzyme sub-types, its unique distribution pattern in the brain as well as its distinct functional and regulatory properties. 

Ferrendelli, J. A. (1978). Distribution and regulation of cyclic GMP in the central nervous system. Adv. Cyclic Nucleotide Res. 9, 453-464. 

In the myocardium, automaticity is the ability of the cardiac muscle to depolarize spontaneously (i.e., without external electrical stimulation from the autonomic nervous system). This spontaneous depolarization is due to the plasma membrane within the heart that has reduced permeability to potassium (K+) but still allows passive transfer of calcium ions, allowing a net charge to build. Automaticity is most often demonstrated in the sinoatrial (SA) node, the so-called pacemaker cells. Abnormalities in automaticity result in rhythm changes. The mechanism of automaticity involves the pacemaker channels of the HCN (Hyperpolarization-activated, Cyclic Nucleotide-gated) family14 (e.g., If, "funny" current). These poorly selective cation channels conduct more current as the membrane potential becomes more negative, or hyperpolarized. They conduct both potassium and sodium ions. The activity of these channels in the SA node cells causes the membrane potential to slowly become more positive (depolarized) until, eventually, calcium channels are activated and an action potential is initiated. 

The stimulation of the octopaminergic nervous system of invertebrates is a proven strategy for the control of important pest species. This has been achieved in the past by the use of octopamine receptor agonists such as formamidine and imidazoline derivatives. However, other potential strategies to achieve this end include the inhibition of cyclic nucleotide phosphodiesterase, inhibition of the neural reuptake of octopamine, and inhibition of octopamine N-acetyltransferase. Using the American cockroach nervous system, formamidines were found to inhibit both the uptake and acetylation of octopamine, but not with a potency comparable to their effect on octopamine receptors. The tricyclic antidepressant, desipramine, and the benzylamine, xylamine, were the most active inhibitors of these octopamine removal systems. The pharmacological profiles for uptake and N-acetylation appear to be quite similar, but differ from that of the adenylate cyclase-linked octopamine receptor. 

Prostaglandins have been associated with neurotransmitter release and synaptic regulation at specific nerve synapses. They have also been reported to influence cyclic nucleotide turnover and the release of anterior pituitary hormones. They may also be involved with fever and temperature regulation. Their participation in many other central nervous system functions as second messengers has also been documented, but in deference to brevity only the topics listed above will be briefly discussed. 

J. Daly, Cyclic Nucleotides in the Nervous System (Plenum Press, New York, 1977). M.J. Berridge and R.F. Irvine, Nature (London), 312 (1984) 315. 

CNG—cyclic-nucleotide-gated channel CNQX—6-cyan o-7-nitroquinoxaline-2,3-dione CNS—central nervous system DHP—1,4-dihydropyridines DAG—1,2-diacylglicerol... 

Caffeine acts as a stimulant of the central nervous system (CNS) through several proposed mechanisms. The most important seems to be its interference with the ability of the neurotransmitter adenosine to bind to its nerve cell receptor. Also, caffeine inhibits the enzyme cyclic nucleotide phosphodiesterase, which breaks down intracellular cyclic adenosine monophosphate (cAMP), another messenger involved in the transmission of nerve signals from hormones originating outside the central nervous system... 

Greengard P (1979) Cyclic nucleotides, phosphorylated proteins and the nervous system. Fed Proc 38 2208-2217... 

Cyclic nucleotides, 3, 5 -cyclic adenosine monophosphate (cAMP) and 3, 5 -cyclic guanosine monophosphate (cGMP), function to regulate cell-to-cell communication processes (33). Cellular communication follows primarily three pathways. The first involves the transmission of electrical impulses via the nervous system. The second involves chemical messengers or hormonal secretions. The third involves de novo protein synthesis. All three processes are usually in response to some demand or stimulus and involve, at least to some extent, regulation by cyclic nucleotides ... 

Cyclic Nucleotides in the Central Nervous System Tamos Bartfai... 

Kurihara, T., and Tsukada, Y., 1967, The regional and subcellular distribution of 2, 3 -cyclic nucleotide 3 -phosphohydrolase in the central nervous system, /. Neurochetn. 14 1167. 

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