Ecabapide (DQ 2511) is a compound with antiulcer and gastroprokinetic activity. Evidence from basic studies in animal models suggests that the drug acts on peripheral mechanisms of neural control. In the stomach, ecabapide acts to suppress firing in vagal afferent nerves and thereby reduce the flow of sensory information into the dorsal vagal complex. The mechanism of action of ecabapide in suppressing discharge in vagal afferent terminals appears to mimic that of nitric oxide by stimulating formation of cGMP and activation of an inhibitory transduction cascade in the sensory fibres. In this respect the mechanism of its pro-kinetic action differs from other promoter agents. Ecabapide development has been discontinued.

Alloyohimbine is an alkaloid, a stereoisomer of yohimbine extracted from Rauvolfia serpentina. Alloyohimbine is a selective antagonist of alpha2-adrenoreceptor.

Ergocristine is an alkoloid originally isolated from Iberian ergot. In the rat, ergocristine acts as an alpha 2-adrenoceptors agonist, and an alpha 1-adrenoceptors antagonist. It is able to regulate glutamate uptake and dopamine release. Ergocristine is controlled as a list I chemical of because it is considered as a chemical precursor used in the illicit manufacture of lysergic acid diethylamide,

Pseudoyohimbine is an alkaloid isolated from roots of Rauwolfia canescens and in trace amount from Uncaria attenuata. Also, it was found in the leaves, stem and bark of Alstonia quaternata and in root bark of Cabucala striolata and Catharanthus trichophyllus. Pseudoyohimbine is inactive in the periphery as well as in the central nervous system as an antagonist of a1- or a2-adrenoceptors.

Idazoxan is an alpha2 receptor antagonist which also shows activity at imidazoline I1 and I2 receptors and modulates the release of dopamine. Idazoxan was in phase II development in the US. Later the development of idazoxan for schizophrenia was discontinued. It was also in clinical trials for cognition disorders in United Kingdom, and was also discontinued. Idazoxan is used in scientific research as a tool for the study of alpha 2-adrenoceptors. Idazoxan`s diastereoisomers possess different relative selectivity for alpha2- pre- and postsynaptic receptors: ( )-idazoxan was 7-8 times more potent than (-)-idazoxan in inhibiting p-[3H]aminoclonidine binding, and 40 times more active in antagonizing clonidine at presynaptic level, indicating a better selectivity for alpha2-presynaptic sites. The pre- and postsynaptic alpha2-adrenoceptors have a different affinity for the two enantiomers of idazoxan. Although the stereoisomers are closely related structurally, ( )-idazoxan possesses a stronger affinity for presynaptic sites. This stereoselectivity was less evident for postsynaptic sites. In rats and dogs, both enantiomers antagonized the sympathoinhibitory effects of clonidine. In rats, ( )- idazoxan was 4-7 times more potent than (-)- idazoxan and 3-8 times more than (-)- idazoxan in dogs. A same order of potency was observed against the sedative effects of clonidine and azepexole in chicks, ( )- idazoxan being 8 times more potent than (-)- idazoxan. Although ( )- idazoxan was more potent than (-) idazoxan, binding studies revealed (-)- idazoxan to be more selective than ( )- idazoxan at central sites. It is concluded that ( )- idazoxan antagonizes both alpha-1 and alpha-2 adrenoceptors and (-)- idazoxan is selective for alpha-2 adrenoceptors. ( )- idazoxan is equipotent for antagonizing postsynaptic alpha-I and alpha-2 adrenoceptors. It is also a potent alpha-2 antagonist at presynaptic and central sites and is 4-8 times more potent than (-)- idazoxan but less selective.

Idazoxan is an alpha2 receptor antagonist which also shows activity at imidazoline I1 and I2 receptors and modulates the release of dopamine. Idazoxan was in phase II development in the US. Later the development of idazoxan for schizophrenia was discontinued. It was also in clinical trials for cognition disorders in United Kingdom, and was also discontinued. Idazoxan is used in scientific research as a tool for the study of alpha 2-adrenoceptors. Idazoxan`s diastereoisomers possess different relative selectivity for alpha2- pre- and postsynaptic receptors: (+)-idazoxan was 7-8 times more potent than (-)-idazoxan in inhibiting p-[3H]aminoclonidine binding, and 40 times more active in antagonizing clonidine at presynaptic level, indicating a better selectivity for alpha2-presynaptic sites. The pre- and postsynaptic alpha2-adrenoceptors have a different affinity for the two enantiomers of idazoxan. Although the stereoisomers are closely related structurally, (+)-idazoxan possesses a stronger affinity for presynaptic sites. This stereoselectivity was less evident for postsynaptic sites. In rats and dogs, both enantiomers antagonized the sympathoinhibitory effects of clonidine. In rats, (+)- idazoxan was 4-7 times more potent than (-)- idazoxan and 3-8 times more than (-)- idazoxan in dogs. A same order of potency was observed against the sedative effects of clonidine and azepexole in chicks, (+)- idazoxan being 8 times more potent than (-)- idazoxan. Although (+)- idazoxan was more potent than (-) idazoxan, binding studies revealed (-)- idazoxan to be more selective than (+)- idazoxan at central sites. It is concluded that (+)- idazoxan antagonizes both alpha-1 and alpha-2 adrenoceptors and (-)- idazoxan is selective for alpha-2 adrenoceptors. In the pithed rat, only (-)- idazoxan possesses both alpha-1 and alpha-2 agonistic effects.

(-)-octopamine is an enantiomer of octopamine, a naturally occurring phenolamine acting as a neurotransmitter in invertebrates. Octopamine is considered to be trace amine present in mammalian tissues at very low (nanomolar) concentrations. Generally, the (-)-enantiomers of octopamine are more active than the (+)-enantiomers at adrenergic receptors. However (+)-octopamine is more potent than the (-)-octopamine as an inhibitor of semicarbazide-sensitive amine oxidase.

(+)-octopamine is an enantiomer of octopamine, a naturally occurring phenolamine acting as a neurotransmitter in invertebrates. Octopamine is considered to be trace amine present in mammalian tissues at very low (nanomolar) concentrations. Generally, the (+)-enantiomers of octopamine are less active than the (-)-enantiomers at adrenergic receptors. However (+)-octopamine is more potent than the (-)-octopamine as an inhibitor of semicarbazide-sensitive amine oxidase.