Opioid receptors mechanisms

Zarrindast MR, Pazouki M, Nassiri-Rad S. (1997). Involvement of cholinergic and opioid receptor mechanisms in nicotine-induced antinociception. Pharmacoi Toxicoi. 81(5) 209-13. 

Talhout R, Opperhuizen A, van Amsterdam JG (2007) Role of acetaldehyde in tobacco smoke addiction, Eur Neuropsychopharmacol 17 627-636 Tanda G, Pontieii FE, Di Chiara G (1997) Cannabinoid and heroin activation of mesolimbic dopamine transmission by a common mul opioid receptor mechanism. Science 276 2048-2050 Taylor JR, Robbins TW (1984) Enhanced behavioural control by conditioned reinforcers following microinjections of d-amphetamine into the nucleus accumbens. Psychopharmacology 84 405 12... 

Tanda G, Pontieri FE, Di Chiara G (1997) Cannabinoid and heroin activation of mesolimbic dopamine transmission by a common ml-opioid receptor mechanism. Science 276 2048-2050. 

Bradley KJ, Headley PM (1997) Effect of agmatine on spinal nociceptive reflex lack of interaction with alpha2-adrenoceptor or mu-opioid receptor mechanisms. Eur J Pharmacol 331 133-138 Brain SD, Cox HM (2006) Neuropeptides and their receptors innovative science providing novel therapeutic targets. Br J Pharmacol 147 8202-8211 Branchek TA, 8mith KE, Gerald C, Walker MW (2000) Galanin receptor subtypes. Trends Pharmacol 8ci 21 109-117... 

It was found that two active metabolites, cj5-A7-(2-aminocyclohexyl)-3,4-dichloro-benzamide (67a) and cis-N-(2-methylamino-cyclohexyl)-3,4-dichlorobenzamide (67b) were formed, each of which was an active anticonvulsant (263). The individual enantiomers were recently evaluated and the (-)-isomer was metabolized to a lesser extent than, the (+)-isomer, which had a lower oral bioavailability as well (267). Fischer et al. independently evaluated U-54494A (268). It was observed in this study that there was considerable evidence to suggest that the stimulation of K-receptors reduces the entry of Ca + into neurons or nerve terminals, which may be related to the closure of N-typeCa channels. This action can result in a decrease of neuronal excitability and a reduction of transmitter release (269-271). Fischer concluded that it was thus difficult to draw definitive conclusions regarding the involvement of central K-opioid receptor mechanisms in the anticonvulsant actions of U-54494A (268). 

It is well established that NF-kB signaling plays a critical role in inflammation and immunity. Understanding the mechanism of NF-kB involvement in opioid receptor activation and chemokine expression may provide a vital key to understanding this complex signaling network. However, the elucidation of molecular mechanisms following activation of the opioid receptor family could aid in the development of future therapeutics for immune system-related and inflammatory diseases, drug addiction and HIV infection. 

Pello OM, Martinez-Munoz L, Parrillas V, Serrano A, Rodiiguez-Frade JM, Toro MJ, Lucas P, Monterrubio M, Martinez A, MeUado M (2008) Ligand stabilization of CXCR4/delta-opioid receptor heterodimers reveals a mechanism for immune response regulation. Eur J Immunol... 

The mu, delta and kappa opioid receptors are coupled to G° and G proteins and the inhibitory actions of the opioids occur from the closing of calcium channels (in the case of the K receptor) and the opening of potassium channels (for /i, d and ORL-1). These actions result in either reductions in transmitter release or depression of neuronal excitability depending on the pre- or postsynaptic location of the receptors. Excitatory effects can also occur via indirect mechanisms such as disinhibition, which have been reported in the substantia gelatinosa and the hippocampus. Flere, the activation of opioid receptors on GABA neurons results in removal of GABA-mediated inhibition and so leads to facilitation. 

Table 21.2 The four opioid receptors with transmitters and drugs acting on the various receptors together with the effector mechanisms and the effects of receptor activation for each receptor...

Figure 21.5 Mechanisms of opioid analgesia at the spinal level. Action potentials in nociceptive afferent fibres invade the terminal and by opening calcium channels (L, N and P-type) cause the release of glutamate and peptides that further transmit pain subsequent to activation of their postsynaptic receptors. Presynaptic opioid receptor activation (mu- and delta-mediated effects have been most clearly shown) opens potassium channels which hyperpolarise the terminal, so reducing transmitter release and inhibiting the postsynaptic neuron...

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