Morphological And Electrophysiological Studies On The Trigeminal Proprioceptive Pathway In The Rat Brain

A possible proprioceptive pathway in the rat was reported by Wang and LI in 1988, the pathway was considered to be composed of four orders of neurons, those were indicated to be located in the mesencephalic trigeminal nucleus (Vme), in the dorsomedial part of subnucleus oral is (Vodm) and adjacent parvocellular reticular nucleus (PCRt), in the "ribbon-shape area" and in the contralateral ventroposterior medial thalamic nucleus (VPM). The "ribbon-shape area" had three enlargements --- dorsomedial part of principal trigeminal sensory nucleus (Vpdm), area ventral to motor trigeminal nucleus (AVM) and area dorsal to superior olivery nucleuus (ADO).This whole dissertation was aimed at the above pathway, in order to confirm the existence of this pathway, and to prove how correct their original propose was. Thus, the whole dissertationcould be divided into two parts-part one, composed of fourstudies, was about the connections of the pathway; and part two,composed of two studies, was tend to the first order neuron -the Vme itself.1. In order to obtain fine structural evidence for the pathway mentioned above, firstly Ricinus communis (Ricin) was injected into the masseter nerve of the rats, and after about two weeks survival HRP was then injected into the "ribbon-shape area". It was observed that electron-dense degenerated terminals synapsed on HRP labeled dendrites. The synapses identified were all the type of asymmetry. The postsynaptic dendrites were mainly primary and intermedial ones.Secondly, kianic acid was injected into the contralateral thalamus. Both filamentous and electron-dense degenerated boutons were seen synapsing on HRP labeled either somata or dendrites in the three enlargements of the "ribbon-shape area".Therefor, connections between first order and second order neurons in the Vodm, and between second order and third order neurons in the "ribbon-shape area" had been electron-microscopically testified.2. It was morphologically demonstracted in the rat that Vme neurons projected to contralateral VPM through another two orders of neuron. Based upon the morphological date, the present work furthered the research by probing functional relationship between the relay neurons mentioned above. Recording micropipette was localized in the Vodm, the Vpdm and AVM, and the contalatral VPM, respectively, unite discharges were found at first. The responses with changing of discharge frequencies to lowering down the jaw, probing the masseter muscle and electric stimulating the...