The Neurochemical Anatomy of Trigeminal Primary Afferent Neurons

The TG represents a cranial analog of the dorsal root ganglia in the peripheral nervous system (Darian-Smith, 1973). TG neurons have a unique morphology and are classified as pseudounipolar (Krastev, 2009). Their centripetal processes, usually called trigeminal primary afferents, carry somatosensory information from mechanoreceptors, thermoreceptors and nociceptors in the face, the oral and nasal cavities, and through the portio major of the trigeminal nerve reach their main target neurons in the trigeminal sensory nuclei (Fig. 1), where they establish synaptic contacts with their perikarya (for reviews, see Darian-Smith, 1973; Dubner et al., 1978; Kruger & Young, 1981).