Striatum

All afferent inputs to the striatum that have been studied so far have formed axonal fields in which the individual axonal branches cross over the dendrites of individual spiny neurons, making synapses mostly en passant. This is the cruciform axodendritic pattern of innervation (Fox et al. 1971), which places each axon into position to contact the maximum number of neurons but minimizes the number of synapses possible with each postsynaptic cell. This is in contrast to the longitudinal axodendritic synaptic arrangement formed by striatopallidal fibers (Fox and Rafols 1976), in which individual axonal branches form multiple synaptic contacts on the dendrites of postsynaptic neurons. 

The striatum comprises the caudate, putamen and nucleus accumbens. In mammals in which corticofugal fibers coalesce into the internal capsule within the striatum, the caudate nucleus and putamen nucleus are separated by this partition. In animals in which corticofugal fibers are dispersed there is no clear separation between these nuclei, thus the term caudate-putamen is often used. The caudate and putamen, in most species, generally occupy the dorsal part of the striatum. The nucleus accumbens is the rostro-ventral extension of the striatum, and occupies the area surrounding the anterior commissure in the rostral part of the striatum. The term ventral striatum is generally used to refer to the nucleus accumbens and more caudally, the ventral most part of the striatum (Fleimer and Wilson 1975). The olfactory tubercle is sometimes included as a part of the ventral striatum, but in this review will not be discussed. 

By combining electron-microscopical immunocytocbemistry with anterograde tracing of corticospinal terminals. Asp was found to be localized in a subpopulation of these terminals (Valtschanoff et al., 1993). However, Asp labeling was much weaker in the identified nerve terminals than in postsynaptic dendritic spines, possibly indicating a metabolic role of Asp. Exocytotic release of Asp should therefore be demonstrated before considering Asp as a transmitter in the corticospinal system. 

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Neuropeptide Y. Neuropeptide Y [82785 5-3] (NPY) (255) is a 36-amiao acid peptide that is a member of a peptide family including peptide YY (PYY) [81858-94-8, 106338-42-5] (256) and pancreatic polypeptide (PPY) [59763-91-6] (257). In the periphery, NPY is present in most sympathetic nerve fibers, particulady around blood vessels and also in noradrenergic perivascular and selected parasympathetic nerves (66). Neurons containing NPY-like immunoreactivity ate abundant in the central nervous system, particulady in limbic stmctures. Coexistence with somatostatin and NADPH-diaphorase, an enzyme associated with NO synthesis, is common in the cortex and striatum. 

OT receptors are localized ia the brain hypothalamus, limbic system, cortex, striatum, olfactory system, and brain stem. In the periphery, OT is best known for its stimulation of uterine smooth muscle and the milk ejection reflex. Thr , Om ]oxytocin(l—8),... 

U (No CaM) i PKA t PKCo/S Heart, brain (striatum) Cardiac function, Ca2+-dependent regulation... 

Multiple sclerosis (MS) 4. In rats with EAE, an animal model of multiple sclerosis, AEA and 2-AG levels are decreased in the striatum and midbrain. This might be associated with motor impairment 4. Inhibitors of degradation (both FAAH and cellular re-uptake)... 

The nigrostriatal tract is one of the four main dopaminergic pathways in the central nervous system. About 75% of the dopamine in the brain occurs in the nigrostriatal pathway with its cell bodies in the substantia nigra, whose axons project in the corpus striatum. Degeneration of the dopaminergic neurons in the nigrostriatal system results in Parkinsons disease. 

The pharmacology of amphetamine is considerably more complex. It does not only block monoamine reuptake, but also directly inhibits the vesicular monoamine transporter, causing an increase in cytosolic but not vesicular dopamine concentration. This may lead to reverse transport of the amines via the membrane-bound transporters. Further mechanisms of amphetamine action are direct MAO inhibition and indirect release of both dopamine and serotonin in the striatum. 

Dopaminergic mechanisms within the ventral striatum (i.e., nucleus accumbens) subserve the ability of amphetamine and methylphenidate in low to moderate doses to increase locomotor activity. In contrast, very low dosages in animals seem to cause hypoactivity presumably by stimulation of autoreceptors, a finding that would be compatible with the clinical impression that methylphenidate might be usefiil in some patients with mania. 

Motor stereotypy Dorsal striatum (i.e., caudate putamen)... 

Localization CNS Hippocampus (CA1, CA3, DG), septum, amygdala, raphe nuclei CNS Striatum, hippocampus (CA1), substantia nigra, globus pallidus, superior colliculi, spinal cord, raphe nuclei CNS like 5-HT1B but at lower densities. CNS Caudate putamen, parietal cortex, fronto-parietal motor cortex, olfactory tubercle, amygdala CNS Cortex, Thalamus, olfactory bulb (rat), claustrum (g-pig), hippocampus (CA3), spinal cord. 

Localization CNS Cortex, hippocampus, striatum, olfactory bulb, spinal cord CA/S not present in adult. CNS Choroid plexus, medulla, pons, striatum, hippocampus (CA1, CA3), hypothalamus, spinal cord CNS Striatum, hippocampus (CA1), substantia nigra, globus pal-lidus. CNS Striatum, brainstem, thalamus, hippocampus, olfactory bulb, substantia nigra... 

High amounts of somatostatin are found in the CNS, the peripheral nervous system, the gut and the endocrine pancreas whereas the kidneys, adrenals, thyroid, submandibular glands, prostate and placenta produce rather low amounts. In particular, the hypothalamus, all limbic structures, the deeper layers of the cerebral cortex, the striatum, the periaqueductal central grey and all levels of the major sensoty pathway are brain areas that are especially rich in somatostatin. Eighty percent of the somatostatin immunoreactivity in the hypothalamus is found in cells of the anterior periventricular nucleus (Fig. 1, [1]). The gut 5 cells of the mucosa and neurons, which are intrinsic to the submucous and... 

There are few reports on the effects of nitrous oxide on dopaminergic neurotransmission. A study in mice showed that nitrous oxide inhalation produced a significant increase in locomotor activity that was antagonized in a dose-dependent fashion by the dopamine synthesis inhibitor a-methyl-/)-tyrosine (Hynes and Berkowitz 1983). Moreover, administration of the D2 antagonist haloperidol also reduced the locomotor activity induced by nitrous oxide (Hynes and Berkowitz 1983). These results suggest that excitatory effects induced by nitrous oxide may be also mediated by dopaminergic neurotransmission. However, other studies have reported that exposure to nitrous oxide resulted in decreased dopamine release by neurons in the striatum (Balon et al. 2002 Turle et al. 1998). 

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