Neurons postsynaptic

Tizanidine (Zanaflex) is classified as an alpha-2 adrenergic agonist, meaning that this drug binds selectively to the alpha-2 receptors in the CNS and stimulates them. Alpha-2 receptors are found at various locations in the brain and spinal cord, including the presynaptic and postsynaptic membranes of spinal interneurons that control alpha motor neuron excitability. Stimulation of these alpha-2 receptors inhibits the firing of interneurons that relay information to the alpha motor neuron that is, interneurons that comprise polysynaptic reflex arcs within the spinal cord.27 Tizanidine appears to bind to receptors on spinal interneurons, decrease the release of excitatory neurotransmitters from their presynaptic terminals (presynaptic inhibition), and decrease the excitability of the postsynaptic neuron (postsynaptic inhibition).40 Inhibition of spinal interneurons results in decreased excitatory input onto the alpha motor neuron, with a subsequent decrease in spasticity of the skeletal muscle supplied by that neuron. 

In all s mapses, the presynaptic cell will always be a neuron. Postsynaptic cells can be either neurons, striated or smooth muscle cells, or gland cells (Figure 7.2a). In the case of skeletal muscle, the presynaptic neuron will be part of the somatic nervous system. In contrast, neurons that project to the heart muscle will be part of the autonomic system - none of us can voluntarily change the heartbeat. While in many synapses the presynaptic and postsynaptic membranes are in close apposition, thus ensuring rapid action, this is not necessarily the case in the effector synapses of the autonomic nervous system, which frequently do not have extremely time-critical missions. 

Craig AM, Blackstone CD, Huganir RL, Banker G (1993) The distribution of glutamate receptors in cultured rat hippocampal neurons postsynaptic clustering of AMPA-selective subunits. Neuron 70 1055-1068. 

Most neurons in the central nervous system are stimulated by L- glutamate, the major excitatory amino acid in the brain. The postsynaptic actions of... 

Neurodegeneration. Figure 3 Illustration of synaptic (neuritic) apoptosis. A pyramidal neuron is depicted with cortical afferents synapsing on its dendrites. Localized apoptotic mechanisms lead to the release of cytochrome c from the mitochondria and an increase in the concentration of activated caspase-3 in a presynaptic terminal that is synapsing on a dendritic spine. Increased caspase-3 activity results in a localized breakdown of this nerve terminal and its synapse. Subsequently, the postsynaptic dendritic spine retracts and disappears (Figure modified from Glantz et al. [5] [3]). 

Nicotine is the main psychoactive ingredient of tobacco and is responsible for the stimulant effects and abuse/ addiction that may result form tobacco use. Cigarette smoking rapidly (in about 3 sec ) delivers pulses of nicotine into the bloodstream. Its initial effects are caused by its activation of nicotinic acetylcholine (nACh) receptors. nACh receptors are ligand-gated ion-channels and pre- and postsynaptically located. Reinforcement depends on an intact mesolimbic dopamine system (VTA). nACh receptors on VTA dopamine neurons are normally activated by cholinergic innervation from the laterodorsal tegmental nucleus or the pedunculopontine nucleus. 

A synapse is a contact site between two neurones, where information is communicated from the axon of one neurone (the presynaptic) to the cell body, the dendrites or the axon of the second neurone (the postsynaptic). In most synapses, the information is communicated chemically ... 

There are numerous transmitter substances. They include the amino acids glutamate, GABA and glycine acetylcholine the monoamines dopamine, noradrenaline and serotonin the neuropeptides ATP and NO. Many neurones use not a single transmitter but two or even more, a phenomenon called cotransmission. Chemical synaptic transmission hence is diversified. The basic steps, however, are similar across all neurones, irrespective of their transmitter, with the exception of NO transmitter production and vesicular storage transmitter release postsynaptic receptor activation and transmitter inactivation. Figure 1 shows an overview. Nitrergic transmission, i.e. transmission by NO, differs from transmission by other transmitters and is not covered in this essay. 

In the venom of C. geographus and other fish-hunting species, the conotoxins isolated so far can be divided into three major classes (1-4) o -conotoxms which block neuronal calcium channels at the presynaptic terminus of the neuromuscular junction, a-conotoxins which inhibit the acetylcholine receptor at the postsynaptic terminus, and x-conotoxins which block Na channels on the muscle membrane. 

While most investigations show that sea snake neurotoxins are postsynaptic type, Gawade and Gaitonde (23) stated that Enhydrina schistosa major toxin has dual actions or postsynaptic as well as presynaptic toxicity. E, schistosa venom phospholipase A is both neurotoxic and myotoxic. Neurotoxic action of the enzyme is weak so that there is sufficient time for myonecrotic action to take place (24), Sea snake, L. semifasciata toxin also inhibits transmission in autonomic ganglia, but has no effect on transmission in choroid neurons. 

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