Synaptic transmission long-term depression

Functions of nNOS include long-term regulation of synaptic transmission in the CNS (long-term potentiation, long-term depression), whereas there is no evidence for an involvement of nNOS-derived NO in acute neurotransmission. Retrograde communication across synaptic junctions is presumed to be involved in memory... 

The CNS contains a substantial amount of nitric oxide synthase (NOS), which is found within certain classes of neurons. This neuronal NOS is an enzyme activated by calcium-calmodulin, and activation of NMDA receptors, which increases intracellular calcium, results in the generation of nitric oxide. Although a physiologic role for nitric oxide has been clearly established for vascular smooth muscle, its role in synaptic transmission and synaptic plasticity remains controversial. Perhaps the strongest case for a role of nitric oxide in neuronal signaling in the CNS is for long-term depression of synaptic transmission in the cerebellum. 

Huang CC, Lo SW, Hsu KS (2001) Presynaptic mechanisms underlying cannabinoid inhibition of excitatory synaptic transmission in rat striatal neurons. J Physiol 532 731—48 Huang YC, Wang SJ, Chiou LC, Gean PW (2003) Mediation of amphetamine-induced long-term depression of synaptic transmission by CB1 cannabinoid receptors in the rat amygdala. J Neu-rosci 23(32) 10311-20... 

Levenes C, Daniel H, Soubrie P, Crepel F (1998) Cannabinoids decrease excitatory synaptic transmission and impair long-term depression in rat cerebellar Purkinje cells. J Physiol (Lond) 510 867-879... 

Figure 10.11. Examples of receptor mediated synaptic plasticity, (a) Long-term potentiation. (LTP). Synaptic transmission at hippocampal synapses (in this example the CA3/CA1 synapse) is potentiated following application of a tetanus (period of rapid stimulation) to the presynaptic nerve. This phenomenon is dependent on the activation of synaptic AMPA and NMDA receptors (see main text), (b) Depolarization snppression of inhibition (DSI). Diagram shows how endocannabinoids prodnce DSI in the hippocampns. Synaptic potentials recorded as hippocampal nenrons are depressed following a tetanns.

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... 

Adman A, Y. Fathollahi, M. Sayyah, M. Kamalinejad, and A. Omrani, 2006. Eugenol depresses synaptic transmission but does not prevent the induction of long-term potentiation in CAl region of rat hippocampal slice. Phytomedicine, 13 146-151. 

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