Spinal cord nuclei

Three tachykinin GPCRs, NK, NK, and NK, have been identified and cloned. AH are coupled to phosphatidjhnositol hydrolysis. The NK receptor is selective for substance P (SP) and is relatively abundant in the brain, spinal cord, and peripheral tissues. The NK receptor is selective for NKA and is present in the gastrointestinal tract, urinary bladder, and adrenal gland but is low or absent in the CNS. The NIC receptor is selective for NKB and is present in low amounts in the gastrointestinal tract and urinary bladder, but is abundant in some areas of the CNS, ie, the spinal dorsal bom, soUtary nucleus, and laminae IV and V of the cortex with moderate amounts in the interpeduncular nucleus. Mismatches in the distribution of the tachykinins and tachykinin receptors suggest the possibility of additional tachykinin receptor subtypes. 

Localisation CA/S Hippocampus (CA1, CA3, DG), cortex, cerebellum (granular layer), olfactory bulb, habenula, spinal cord CA/S Caudate putamen, olfactory tubercle, nucleus accumbens, cortex, hippocampus (CA1, CA3, DG) CA/S Hippocampus (CA1, CA2), hypothalamus, thalamus, superior colliculus, raphe nuclei... 

Substance P is a member of a group of polypeptides known as neurokinins or tachykinins. It is thought to be the primary neurotransmitter for the transfer of sensory information from the periphery to the spinal cord and brain. Substance P as well as neurokinin NKX receptors has been detected in vagal afferent neurons in the area postrema, nucleus tractus solitarius and dorsal motor nucleus of the vagus. Substance P has been shown to increase the firing rate of neurons in the area postrema and nucleus tractus solitarius and to produce retching when applied directly to these areas in animal studies. 

Figure 22.8 The distribution of brainstem Raphe nuclei. Neurons that release 5-HT are clustered in two groups of nuclei in the pons and upper brainstem. The superior group, which projects to forebrain areas, includes the dorsal Raphe nucleus (DRN) and the median Raphe nucleus (MRN). The inferior group projects to the medulla and spinal cord and includes the nucleus Raphe pallidus (NRP), the nucleus Raphe obscurus (NRO) and the nucleus Raphe magnus (NRM)...

Nucleus A group of specialized nerve cells or a localized mass of gray matter in the brain or spinal cord. 

Figure 8.2 The endogenous analgesic system. The three major components of the endogenous analgesic system include the periaqueductal gray matter in the midbrain nucleus raphe magnus in the medulla and pain inhibitory complex in the dorsal horns of the spinal cord. This system causes presynaptic inhibition of pain fibers entering the spinal cord. The binding of enkephalin to opioid receptors on the pain fibers prevents release of the neurotransmitter, substance P. As a result, the pain signal is terminated in the spinal cord and does not ascend to higher centers in the CNS.

Narcolepsy, a sleep disorder characterized by excessive daytime sleepiness and cataplexy, may be caused by the lack of hypocretin mRNA and peptides in humans (Peyron et al., 2000) or a disruption of the hypocretin receptor 2 or its ligand in dogs and mice (Lin et al., 1999 Chemelli et al., 1999). Hypocretin-containing neurons are located exclusively in the dorsomedial, lateral, and perifornical hypothalamic areas (Peyron et al., 1998). Two hypocretin sequences, Hcrt-1 (orexin-A) and Hcrt-2 (orexin-B), are generated from a single preprohypocretin (De Lecea et al., 1998 Peyron et al, 1998 Sakurai et al, 1998). Axons from these neurons are found in the hypothalamus, locus coeruleus (LC), raphe nuclei, tuberomamillary nucleus, midline thalamus, all levels of spinal cord, sympathetic and parasympathetic centers, and many other brain regions... 

FIGURE 1-15 A myelinating oligodendrocyte, nucleus (N), from the spinal cord of a 2-day-old kitten extends cytoplasmic connections to at least two myelin sheaths arrows). Other myelinated and unmyelinated fibers at various stages of development, as well as glial processes, are seen in the surrounding neuropil. Xl2,750. 

FIGURE 1-16 A microglial cell (M) has elaborated two cytoplasmic arms to encompass a degenerating apoptotic oligodendrocyte (O) in the spinal cord of a 3-day-old kitten. The microglial cell nucleus is difficult to distinguish from the narrow rim of densely staining cytoplasm, which also contains some membranous debris. xl0,000. 

Hippocampus, entorhinal cortex, amygdala, nucleus, accumbens, solitary tract nerve, trigeminal nerve, motor nucleus of the dorsal vagal nerve, area postrema, spinal cord... 

X2 NM 174873 Sensory and autonomic ganglia, dorsal and ventral horn of the spinal cord, thalamus, hypothalamus, preoptic area, red nucleus, oculomotor nucleus, locus coeruleus and dorsal motor nucleus of the vagus... 

X3 NM 002559 Dorsal root ganglion, superficial dorsal horn of spinal cord, a subset of small-diameter sensory neurons, nucleus of the solitary tract, spinal trigeminal nucleus (important for peripheral pain)... 

FIGURE 45-8 Tau protein immunoreactivity in brains and spinal cords from mice transgenic for mutant (P301S) human tau protein. (A, B) Cerebral cortex. (C) Amygdala. (D) Dentate nucleus of the cerebellum. (E, F) Brainstem. (G, H) Spinal cord. Scale bars (A-C, E, F), 40 pm (in A) (D, H) 60pm (in D) (G), 250pm. 

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