Neuropeptides Neurotransmitters

In the trans Golgi compartment the peptide is sorted via secretory vesicles into a regulated pathway. In contrast to vesicles of the constitutive pathway, vesicles of the regulated pathway are stored in the cytoplasm until their stimulated release. Membrane depolarisation as well as a wide range of substances such as intracellular mediators, neuropeptides, neurotransmitters, classical hormones, cytokines, growth factors, ions and nutrients induce somatostatin secretion. General inhibitors of somatostatin release are opiates, GABA, leptin and TGF- 3. 

Next, this RNA is translated into a pre-propeptide, which enters the endoplasmic reticulum (Fig. 1—9). This is the precursor of a precursor, sometimes also called the grandparent of the neuropeptide neurotransmitter. This pre-propeptide grandparent neuropeptide has a peptide tail, called a signal peptide, which allows the pre-propeptide to enter the endoplasmic reticulum, where the tail is clipped off by an enzyme called a signal peptidase with formation of the propeptide, or parent of the neuropeptide. The propeptide is the direct precursor of the neuropeptide neurotransmitter itself. 

This parental propeptide then leaves the endoplasmic reticulum and enters synaptic vesicles, where it is finally converted into the neuropeptide itself by a converting enzyme located there. Since only the synaptic vesicles loaded with neuropeptide neurotransmitters and not the synthetic enzyme machinery to make more neuropeptides, are transported down to the axon terminals, no local synthesis of more neuropeptide neurotransmitter can occur in the axon terminal. 

In addition to the cholinergic deficit, Alzheimer s disease has also been shown to be characterized by marked deficits in the monoamine neurotransmitters norepinephrine and serotonin, as well as in glutamate and some neuropeptide neurotransmitters (Figure 27.6). 

I.S. Marton and M. Szondy, Possible neuroendocrine hazards of prenatal steroid exposure, in E. EndrOczi, L. Angelucci, V. Scapagnini and D. De Vied (Eds.), Neuropeptides, Neurotransmitters and Regulation of Endocrine Processes, Akademiai Kiado, Budapest, 1983 , pp. 535-543. 

Neurotransmitters and neuropeptides Neurotransmitters are released from the presynaptic cell into the tiny volume defined by the synaptic cleft. Individual neuron contains only very small quantities of the transmitter. The released transmitter then diffuses across the cleft and binds to receptors on the post-synaptic cell. The diffusion across the short distance that separate pre- and post-synaptic neurons is fast enough to allow rapid communication between nerves or between nerve and muscle at a neuromuscular junction. acetylcholine, adrenaline noradrenaline, dopamine, serotonin, glutamate, glycine, GABA, enkephalins, substance P, angiotensin II, somatostatin... 

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