Hormone interaction antagonism

Much like the phenolic acids, early work with scopoletin showed it inhibited oxidation of IAA and thus could affect growth in this manner. Inhibition of several other enzymes by scopoletin and coumarin has been shown. Coumarin was reported to induce ethylene synthesis.47 Also, it is one of several phenolic compounds that antagonize abscisic acid-induced inhibition of growth and stomatal closure.52 Undoubtedly, these and possibly other interactions with hormones are part of the physiological action of the coumarins. 

The increase in neuropeptide Y results in an increase in food intake. Obesity in the normal mouse results in an increase in plasma leptin, where increased levels of leptin at the leptin receptor (in the hypothalamus) provokes an increase in melanocortin (MSH). The increase in MSH in the brain pnjvokes an increase in stimulation of the melanocortin-4 receptor in the brain, which results in a decline in food intake- MSH is the hormone that binds to melanocortin receptors, where this interaction can be antagonized if agouti protein is allowed to contact the receptor. 

There are four major families of receptors that drugs, which mimic, modify, or antagonize endogenous neurotransmitters, hormones, or autocoids, are capable of interacting with in the body (Fig. 4.8). Some receptors allow a rapid response to a released neurotransmitter/hormone... 

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