Short-term synaptic depression

Retrograde Endocannabinoid Signaling in Short-Term Synaptic Depression.447... 

Buspirone. Hie initial compound in this series, buspir-one (BuSpar). has anxiolytic and antidepre.ssnnt activities and is a partial. iHTiA agonist. Its anxiolytic activity is reportedly due to its ability to diminish. -ITT release (via. SHTia agonism). High short-term synaptic levels of. S-HT ate characteri.stic of anxiety. Also, since it is a partial agoni.st. it can stimulate postsynaptie receptors when 5-HT levels are low in the synapse, as is the case in depression. A number of other spirones are in development as anxiolytics and antidepressants. ... 

Synaptically Driven EC-Dependent Short-Term Depression.451... 

In addition to their short-term effects, cannabinoids also modulate the induction of long-term synaptic plasticity. Administration of THC and the endocannabinoids anandamide and 2-AG inhibits the induction of long-term potentiation (LTP) in the hippocampus (Nowicky et al. 1987 Terranova et al. 1995 Stella et al. 1997) and long-term depression (LTD) within the cerebellum and nucleus accumbens (Levenes et al. 1998 Hoffman et al. 2003a). 

Endocannabinoid activation of CBi receptors is likely to be involved in the induction, but not in the maintenance of long-term synaptic plasticity because CBl antagonists impair long-term depression only when applied either prior to, or within 5 to 10 min of LTD induction (Chevaleyre and Castillo 2003 Ronesi et al. 2004) (Fig. 2A). The difference between short- and long-term synaptic effects of endocannabinoids may be due to the duration (or type) of endocannabinoid release, and sustained (for several minutes) activation of presynaptic CB i receptors (note DSI has a shorter time course). The mechanisms by which CBi activation induces long-term changes remain to be resolved, but the induction is unlikely to be solely due to CBi activation (Ronesi et al. 2004). 

St. John s wort Hypericum perforatum), an herb used extensiveiy in the treatment of miid to moderate depression in Europe, has aroused interest in the United States. A bushy, iow-growing plant covered with yeiiow fiowers in summer, St. John s wort has been used for centuries in many folk and herbal remedies. In Germany, hypericum is used in the treatment of depression more than any other antidepressant. The scientific studies that have been conducted regarding its use have been short-term, however, and have used several different doses. St. John s Wort works like the SSRIs, in that it not only increases the availability of 5-HT in synaptic clefts by blocking its reuptake but also increases the availability of NE, which increases energy and alertness, and dopamine, which increases the feeling of well-being. 

Implicit in such a self-tuning regulator model is the assumption that afferent inputs may up- or down-regulate the RCPG by inducing synaptic potentiation or depression of neural transmission. Respiratory short- and long-term potentiation have been variously reported as indicated above. The possibility of synaptic depression was recently demonstrated in the nucleus tractus solitarius of the medulla (Zhou... 

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