Antagonistic attribute

Interestingly, the antagonist activity of ICI and other antiestrogens has also been recently attributed to the ability of these compounds to induce degradation of the ER protein in estrogen target tissues. It is thought that... 

In the periphery, some of the primary triggers for these processes have been identified. Acetylcholine seems to be one such factor because stimulation of preganglionic nerves in vivo increases enzyme activity. However, nicotinic and muscarinic receptor antagonists do not completely prevent this increase. The residual activation is attributed to peptides of the secretin-glucagon subgroup, including VIP and secretin both these peptides activate cAMP synthesis. Purinergic transmitters could also be involved. 

Cimetidine and other imidazole-containing H2 receptor antagonists scavenge hydroxyl radicals at a frster rate than mannitol. This activity was attributed to the methyl imidazole moiety rather than the guanidine of cimetidine (Ching etal., 1993). 

The renaissance of the Biginelli MCR can be attributed to the obtained pyrimidine derivatives, which show remarkable pharmacological activity. A broad range of effects, including antiviral, antitumor, antibacterial, anti-inflammatory as well as antihypertensive activities has been ascribed to these partly reduced pyrimidine derivatives [96], such as 9-117 and 9-118 (antihypertensive agents) [97] and 9-119 (ala-adrenoceptor-selective antagonist) [98] (Scheme 9.24). Recently, the scope of this pharmacophore has been further increased by the identification of the 4-(3-hydroxyphenyl)-pyrimidin-2-thione derivative 9-120 known as monastrol [98], a novel cell-permeable lead molecule for the development of new anticancer drugs. Monastrol appears specifically to affect cell division (mitosis) by a new mechanism,... 

Prazosin is a selective aradrenergic receptor antagonist that, at therapeutic doses, has little activity at a2-adrenergic receptors and clinically insignificant direct vasodilating activity The drug does not cause the other effects attributed to phentolamine. Most important, it produces less tachycardia than does phentolamine and, therefore, is useful in the treatment of essential hypertension. 

The stimulatory effects of H3 antagonists on brain histamine dynamics were initially attributed to the... 

BK currents consisted of transient and steady-state components. The transient currents were abolished by ryanodine (10 fiM), indicating that they are activated by Ca2+ sparks. The lag from the onset of depolarization (activation of VDCCs) to the first transient BK current was around 50 ms. This delay is much too long to be attributed to local signalling from VDCCs to RyRs such as occurs in heart, and instead is consistent with the idea of loose coupling between VDCCs and RyRs (Fig. 1 A) (Collier et al 2000). Spark-activated transient BK currents remained in the presence of the VDCC antagonist diltiazem (50 //M). However, the frequency of... 

Most of the data reported thus far indicate that hallucinogens can have fa-cilitatory effects on MSRs and PSRs in spinalized animals, and that these effects occur in both flexors and extensors. Furthermore, since these effects are reversed by antagonists, they may be attributed to stimulation of excitatory postsynaptic 5-HT receptors that have been shown to facilitate motoneuron activation in the ventral horn of the spinal cord (134). 

Electrical stimulation in the vicinity of the raphe nuclei has been reported to produce depressant effects on MSRs (32,142). These depressant effects could be attributed to activation of postsynaptic inhibitory receptors analogous to those characterized in the forebrain, except for the fact that the depression was blocked by 5-HT antagonists. The effectiveness of the antagonists suggests that the receptor is more akin to the excitatory 5-HT receptor characterized on motoneurons (134,184). The depressant behavioral effects could result from... 

Since most of the effects of hallucinogens on unconditioned behavior are blocked by 5-HT antagonists, their effects can be attributed to actions at these excitatory postsynaptic receptors. These behaviors include most of the actions of hallucinogens on spinal reflexes, the excitatory effects of at least one hallucinogen (5-MeODMT) on acoustic startle, and the production of the 5-HT syndrome, limb flicks, and limb jerks. 

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