Agonists depression

Warnock JK, Bundren JC, Morris DW. Depressive symptoms associated with gonadotropin-releasing hormone agonists. Depress Anxiety 1998 7(4) 171-7. 

Systemical or intranigral application of dopamine receptor agonists depresses the firing of nigrostriatal dopamine cells by stimulating soma-dendritic autoreceptors in the zona compacta, an effect again antagonized by neuroleptics (110, 111, 112). ... 

Inhibits prolactin release (D2-R agonist) [depressant, hallucinogenic]... 

VUazodiuie SSRI and 5-HTlA Partial Agonist (Depression). 23... 

Future Outlook for Antidepressants. Third-generation antidepressants are expected to combine superior efficacy and improved safety, but are unlikely to reduce the onset of therapeutic action in depressed patients (179). Many dmgs in clinical development as antidepressive agents focus on estabhshed properties such as inhibition of serotonin, dopamine, and/or noradrenaline reuptake, agonistic or antagonistic action at various serotonin receptor subtypes, presynaptic tt2-adrenoceptor antagonism, or specific monoamine—oxidase type A inhibition. Examples include buspirone (3) (only... 

Some P-adrenoceptor blockers have intrinsic sympathomimetic activity (ISA) or partial agonist activity (PAA). They activate P-adrenoceptors before blocking them. Theoretically, patients taking P-adrenoceptor blockers with ISA should not have cold extremities because the dmg produces minimal decreases in peripheral blood flow (smaller increases in resistance). In addition, these agents should produce minimal depression of heart rate and cardiac output, either at rest or during exercise (36). 

Another major second messenger in cells is calcium ion. Virtually any mammalian cell line can be used to measure transient calcium currents in fluorescence assays when cells are preloaded with an indicator dye that allows monitoring of changes in cytosolic calcium concentration. These responses can be observed in real time, but a characteristic of these responses is that they are transient. This may lead to problems with hemi-equilibria in antagonist studies whereby the maximal responses to agonists may be depressed in the presence of antagonists. These effects are discussed more fully in Chapter 6. 

A characteristic of hemi-equilibria is the observation of a depressed plateau of maximal responses. Thus, while a truly insurmountable antagonist will eventually depress the concentration-response curves to basal levels hemi-equilibrium conditions can produce partial but not complete inhibition of the agonist maximal response. This is shown in Figure 6.21. 

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