| The interstitial nucleus of the spinal trigeminal (INV) is diffuse groups of neurons and neuropils located within the spinal trigeminal tract along the dorsolateral edge of the spinal trigeminal subnucleus caudalis (Vc) and interpolaris (Vi). It mainly consists of the dorsal paramarginal nucleus (PaMd) and the paratrigeminal nucleus (PaV) and receives the orofacial somatic and visceral primary inputs via branches of the trigeminal nerves (V), the glossopharyngeal (IX) and vagus (X) nerves. It plays an important role in convergence and transmission of the orofacial somatic and visceral nociceptive information, as well as modulation of the visceral and cardiovascular activities.There are many kinds of neuroactive substances related to transmission and modulation of the nociceptive information, such as L-ENK, substance P (SP), CGRP and so on in INV. The calbindin D-28k (CB) is an important member of the family of calcium-binding proteins. CB might buffers intracellular Ca2+ induced by W-methyl-D-aspartate (NMDA) receptor activity, and thus prevent from excitotoxic effects of high-frequency discharge of nociceptive afferent fibers. CB might also reduce the Ca2+-dependent K+ outflow, decrease the amplitude of the hyperpolarization and increase the discharge rate, so that it shorten the refractory period and speed up the transmission of nerve messages. In resent years, it has been studiedthat the distributions and functions of the CB-containing neurons in the central nervous system (CNS). CB always exists in nuclei relevant with transmission of the sensory, especially nociceptive, information in the dorsal corns of the spinal cord and the medulla oblongata. For instance, the CB-containing neurons coexist with glutamate (Glu) in the Golgi type I neurons in lamina I of spinal cord dorsal horn and project to the nucleus of the solitary tract (NTS); CB-containing neurons in the superficial lamina of dorsal horn of the medulla oblongata receive orofacial somatic nociceptive information and project to parabrachial nucleus (PEN); CB-containing neurons in NTS receive visceral nociceptive information and project to bed nucleus of the stria terminals and the like. It is suggested that CB-containing neurons might be involved in processing nociceptive information. Up to now, it is unknown whether CB-containing neurons in INV directly receive the orofacial somatic and visceral nociceptive information; whether they coexist with Glu and may be inhibited by gamma-aminobutyric acid (GABA); whether the orofacial and visceral peripheral nociceptive information converge onto the same CB-containing neurons and form synaptic connections with primary afferent terminals.The above mentioned questions were studied using retrograde and transganglionic tracing methods combined with immunofluorescence histochemical and confocal scanning and electron microscopic immunohistochemical technique in present study.Most of FG-retrograde labeled neurons (74.4%) in INV were double-labeled with CB, and approximate 41.0%, 47.4% and 32.5% of the double-labeled neurons with FG/CB might receive nociceptive information from orofacial superficial, deep structures and visceral organs, following injections of floro-gold (FG) into NTS unilaterally and formalin into lips, masseter muscle or upper alimentary tract, respectively. While after injections of FG into PBN unilaterally and formalin into lips or upper alimentary tract, a majority of the FG-retrograde labeled neurons (77.3%) in INV were double-labeled with CB, and about38.5% and over half (52.0%) of those double-labeled neurons with FG/CB might receive orofacial somatic superficial structural and visceral nociceptive information, respectively.Phosphate-activated glutaminase (PAG) is a major synthetic enzyme of glutamate (Glu) and also a special marker for glutamatergic neurons. Using FG-retrograde tracing methods combined with PAG and CB or PAG and Fos protein immunofluorescence histochemical triple-labeled technique, over quarter (26.6%) of CB-containing neurons in INV displayed PAG- immu...
|
PDF Full Text Request