Interaction agonistic

The broad physiological effects of EA are based mostly on their interaction with the neurotransmitter receptors on the cells. The presence of hidden structures resembling some important neurohumoral mediators (e.g., noradrenaline, serotonin, dopamine) (Scheme 1) in the molecules of EA could explain their interactions (agonistic or antagonistic) with these receptors [2]. 

Jaeger (1981) looked at the interactive agonistic behavior of Plethodon cinereus that were either familiar or unfamiliar with each others pheromones. Using a variation of experimental procedure (2),... 

Nicotinic Receptor Agonists. There has been significant activity in the development of muscarinic cholinergic receptor agonists for dementia. In addition, agents that interact with nicotinic cholinergic receptors may also have therapeutic value. Nicotinic receptors have been reported to be... 

The spatial and steric requirements for high affinity binding to protein kinase C (PKC), a macromolecule that has not yet been crystallized, were determined. Protein kinase C plays a critical role in cellular signal transduction and is in part responsible for cell differentiation. PKC was identified as the macromolecular target for the potent tumor-promoting phorbol esters (25). The natural agonists for PKC are diacylglycerols (DAG) (26). The arrows denote possible sites of interaction. 

Fig. 10. The postulated interaction of a-adrenoceptor agonists with the receptor. The Easson-Stedman hypothesis suggests that (R)-noradrenaline is most potent owing to its three points of attachment () to the adrenoceptor, whereas dopamine and (5)-noradrenaline are equal in activity, but less active...

In contrast, interactions of competitive antagonists and receptors are relatively straightforward. It can be shown by comparing the equal responses provided by an agonist, [ ], alone or in the presence of a competitive antagonist, so that... 

The term endocrine disrupter (ED) has tended to be used for those chemicals which act specifically at the level of the hormone receptor present in the target cells of various organs. Such chemicals may either mimic the action of the natural hormone (agonistic activity) or are sufficiently similar in molecular shape to the naturally produced hormone to interfere with the interaction between the hormone and receptor, thus blocking or impeding the activation of the receptor (antagonsitic activity). Such effects may occur at very low concentrations (as with the endogenous hormone), compared with the concentrations normally required to elicit the more traditional toxic effects attributed to chemicals. Recently,... 

There are even receptors that are known to become activated only due to interaction with a synthetic chemical, and no physiological agonist for such a receptor has been characterized. A model receptor in this class is the so-called Ah receptor complex that becomes activated subsequent to its exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxiu (TCDD). Activation of the. Ah receptor... 

The ergolines have provided a number of drugs that show interaction with neurotransmitters. Depending on the substitution pattern, they may be dopamine agonists or antagonists, a-adrenergic blockers, or Inhibitors of the release of prolactin. A recent member of the series, pergolide... 

FIGURE 1.5 Schematic diagram of response production by an agonist. An initial stimulus is produced at the receptor as a result of agonist-receptor interaction. This stimulus is processed by the stimulus-response apparatus of the cell into observable cellular response. 

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