Trigeminal

Odors are perceived via the olfactory system, which is composed of two organs in the nose the olfactory epithelium, a very small area in the nasal system, and the trigeminal nerve endings, which are much more widely distributed in the nasal cavity (11). The olfactory epithelium is extremely sensitive, and humans often sniff to bring more odorant in contact with this area. The trigeminal nerves initiate protective reflexes, such as sneezing or interruption of irrhalation, with exposure to noxious odorants. 

Peripheral Cholinergic heteroreceptor -myenteric plexus Peripheral Vascular smooth muscle, autonomic terminals Peripheral autonomic and trigeminal nerve terminals Peripheral None identified ... 

TK NKxr displays a broad distribution in both peripheral tissues and in the central nervous system (CNS). In both CNS and enteric neurons, NKxr stimulation increase their excitability, whereas in trigeminal ganglion neurons SP has no intrinsic electrophysio-logical effects but is capable to enhance the amplitude of the inward current induced by the stimulation of serotonin 5-HT3 recqrtors. This enhancement dqjends on the activation of PKC via the stimulation of NKX recqrtors. This is an interesting case of receptor cross talk. Other functions of NKxr have been also highlighted. 

TRPVl, also known as the capsaicin- or vanilloid-receptor, is a nonselective cation channel expressed e.g., in neurons of the dorsal root and trigeminal ganglions, which integrates multiple pain-producing stimuli including heat, protons, capsaicin, and resiniferatoxin. In addition, TRPVl currents can be activated by ananda-mide, protein kinase C (PKC), and by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). 

Cardiac-changes in pulse rate or rhythm electrocardiographic changes, such as bradycardia, tachycardia, premature ventricular contractions, bigeminal (two beats followed by a pause), or trigeminal (three beats followed by a pause) pulse. Other arrhythmias (abnormal heart rhythms)also may be seen. 

Thyrotoxicosis Pheochromocytoma Myotonic dystrophy Trigeminal neuralgia... 

Exposures of 10 weeks (5 days/week) to 2,500 mg/kg/day trichloroethylene in com oil by gavage resulted in altered myelin thickness in the rat mental nerve, a branch of the trigeminal nerve (Barret et al. 1991). Effects of similar exposures on the rat trigeminal nerve included decreased fiber diameter and altered fatty acid composition in total lipid extracts, indicative of demyelination (Barret et al. 1992). Stronger effects were seen with the trichloroethylene decomposition product dichloroacetylene. 

Barret L, Torch S, Leray CL, et al. 1992. Morphometric and biochemical studies in trigeminal nerve of rat after trichloroethylene or dichloroacetylene oral administration. Neurotoxicology 13 601-614. 

Barret MD, Garrel S, Danel V, et al. 1987. Chronic trichloroethylene intoxication A new approach by trigeminal-evoked potentials. Arch Environ Health 42 297-302. 

Dogui M, Mrizak N, Yacoubi M, et al. 1991. Trigeminal somatosensory evoked potentials in workers handling trichloroethylene. Neurophysiol Clin 21 95-103. 

Feldman RG, Niles C, Proctor SP, et al. 1992. Blink reflex measurement of effects of trichloroethylene exposure on the trigeminal nerve. Muscle Nerve 15 490-495. 

GlaserMA. 1931. Treatment of trigeminal neuralgia with trichloroethylene. JAMA 96 916-920. 

Lawrence WH, Partyka EK. 1981. Chronic dysphagia and trigeminal anesthesia after trichloroethylene exposure. Arm Intern Med 95 710. 

Leandri M, Schizzi R, Scielzo C, et al. 1995. Electrophysiological evidence of trigeminal root damage after trichloroethylene exposure. Muscle Nerve 18 467-468. 

Direct attenuation of the excitability of neurons in the trigeminal nuclei, as 5-HTib/ 5-HTid receptors on pain transmission neurons in the trigeminal nucleus caudalis and in the upper cervical cord, are activated. Stimulation of these receptors is caused by second-generation triptans that cross the blood-brain barrier such as zolmitriptan, naratriptan, rizatriptan and eletriptan. 

Absence from the first developmental stages as in whales and some Old World monkeys suggests that functional substitution is provided by other nasal chemoreceptors. The ganglia and fibres of the terminal nerve system (N. terminalis, Fig. 2.9) are the principal candidate (Wirsig and Leonard, 1987). The role of the trigeminal input, although a minor sensor, could well be expanded in a limited capacity (Tucker, 1971 Wysocki and Meredith, 1987 Westhofen, 1987). 

Bojsen-Mpller F. (1975). Demonstration of terminalis, olfactory, trigeminal and perivascular nerves in the rat nasal septum. J Comp Neurol 159, 245-256. 

Devitsina G.V. and Cherova L. (1992). The trigeminal nerve system and its interaction with olfactory and taste system in fishes. In Chemical Signals in Vertebrates 6 (Doty R.L. and Miiller-Schwarze D., eds.). Plenum, New York, pp. 85-88. 

Tucker D. (1971). Non-olfactory responses from nasal cavity Jacobson s Organ and trigeminal system. In Handbook of Sensory Physiology Chemical Senses, 1. Olfaction (Biedler L., ed.). Springer, Berlin, pp. 151-181. 

Westhofen M.C. and Herberhold C. (1987). Trigeminal and olfactory synergism in the perception of smell. Acta Oto-Rhino-Laryngol Belg 41, 66-71. 

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