Action potential active ester

In parallel with the identification of distinct transporters for GABA there has been continued interest in the development of selective blockers of these transporters and the therapeutic potential that could result from prolonging the action of synaptically released GABA. It has been known for a long time that certain pro-drugs of nipecotic add (e.g. nipecotic acid ethyl ester) are able to cross the blood-brain barrier and are effective anticonvulsants in experimental models of epilepsy. More recently, several different systemically active lipophillic compounds have been described that act selectively on GAT-1, GAT-2 or GAT-3 (Fig. 11.4). Of these, tiagabine (gabitiil), a derivative of nipecotic acid that acts preferentially on GAT -1, has proved clinically useful in cases of refractory epilepsy. 

The remainder of the radioactivity is associated with three main phospholipid classes, namely, phosphatidylcholine, phosphatidylethanolamine, and the phosphoinositides, mainly PIP2. Nonetheless, this type of result is commonly attributed to the action of a phospholipase A2, which is activated upon agonist interaction with the platelet. The other presumed product, a lysolecithin, would not be labeled in the above experimental protocol and thus, due to the very small amount formed in the reaction, could not be detected. Though one could potentially label the polar head group of the parent phosphoglycerides, there is little need to do so since the arachidonic acid is associated almost exclusively with the sn-2 ester position on phosphoglycerides. Consequently, the release of free arachidonic acid can be safely attributed to phospholipase A2 activity. While the yield of arachidonic acid is very low, the activation of the cell occurs only over a short time span, anywhere from 5 sec to 1 min. Thus self-control of cell activation is evident. 

CO-beneldopa benserazide levodopa. cocaine (ban, usan] (cocaine hydrochloride (jan, usan)) is an ester of benzoic acid and methylecgonine and the principal alkaloid of Erythroxylum coca and other Erythroxylum spp. (Erythroxylaceae). It is a LOCAL ANAESTHETIC (used topically because of toxicity), and has pronounced indirect-acting SYMPATHOMIMETIC actions by virtue of being an UPTAKE INHIBITOR (interferes with Uj active uptake of noradrenaline into noradrenergic nerve terminals). It is a VASOCONSTRICTOR and can be used as a topical mydriatic and ocular diagnostic agent. It is a powerful CNS stimulant (similar in action to amphetamine), with considerable abuse potential, cocaine hydrochloride cocaine. 

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