Primary afferent sensory neurons

The areas expressing // receptor mRNA corresponded to those found to express // receptor binding sites and // receptor immunoreactivity [37—41]. In most brain and spinal cord regions, // receptor immunoreactivity was detected in cell bodies and dendrites of neurons [39—41]. Immunoreactivity was also detected in superficial layers of the dorsal hom, which contain primary afferent sensory input /x re-... 

The nervous system is divided into two parts the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all afferent (sensory) neurons, which carry nerve impulses into the CNS from sensory end organs in peripheral tissues, and all efferent (motor) neurons, which carry nerve impulses from the CNS to effector cells in peripheral tissues. The peripheral efferent system is further divided into the somatic nervous system and the autonomic nervous system. The effector cells innervated by the somatic nervous system are skeletal muscle cells. The autonomic nervous system innervates three types of effector cells (1) smooth muscle, (2) cardiac muscle, and (3) exocrine glands. While the somatic nervous system can function on a reflex basis, voluntary control of skeletal muscle is of primary importance. In contrast, in the autonomic nervous system voluntary control can be exerted, but reflex control is paramount. 

Small quantities of opiate injected intrathecally or epidurally produce segmental analgesia. This observation led to the clinical use of spinal and epidural opiates during surgical procedures and for the relief of postoperative and chronic pain. As with local anesthesia, analgesia is confined to sensory nerves that enter the spinal cord dorsal horn in the vicinity of the injection. Presynaptic opioid receptors inhibit the release of substance P and other neurotransmitters from primary afferents, whereas postsynaptic opioid receptors decrease the activity of certain dorsal horn neurons in the spinothalamic tracts. 

Capsicum, also known as chili or paprika, is the fruit of various Capsicum species. It is widely used as a spice and, traditionally, it has been used internally for colic, flatulent dyspepsia, chronic laryngitis, insufficiency of peripheral circulation, and externally for neuralgia. Capsaicin (the active pungent ingredient) has been used extensively as a probe to elucidate the function of sensory neurons in various organs and systems (including the stomach), because of its ability to excite and later defunctionalize a subset of primary afferent neurons. 

While it is clear from a number of studies that Kv7 currents regulate membrane potential in central neurons, the data supporting a similar role in primary sensory afferents are not as well established. Several studies, however, do support a similar role for Kv7 channels in sensory neurons. 

Substance P, an undecapeptide, is a member of the tachykinin peptide group. It is an important sensory neuron transmitter in the ENS and, of course, in primary afferents involved in nociception. Substance P contracts intestinal and bronchiolar smooth muscle but is an arteriolar vasodilator (possibly via NO release). It may also play a role in renal and salivary gland functions. 

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