Organization within the cranial IX–X complex in ranid frogs: A horseradish peroxidase transport study

Abstract

Cranial nerves IX and X in frogs have been described as originating from a nuclear group referred to as the IX-X complex. We studied the central nervous system components of this complex in Rana pipiens and R. catesbiana by labeling peripheral branches of cranial nerves IX and X and identifying the central nervous system contributions of these branches. Various peripheral nerves (IX and the cardiac, gastric, pulmonary, and laryngeal branches of X) were identified and soaked in horseradish peroxidase (HRP). One to 2 weeks later, the frogs were killed and processed for HRP by the tetramethylbenzidine method. Glossopharyngeal efferents originated from a small ventrolateral cell group found at the level of IX root exit. Vagal efferents formed a single column of cells in a ventrolateral position from the level of the brainstem exist of the vagus nerve (approximately 2,000 micrometers above the obex) to 200 micrometers below the obex (values given are for an 80-g frog). This cell group was separate from and just caudal to efferent cells of the glossopharyngeal nerve. Within the vagal portion of the column, cells projecting through the gastric branch were found throughout the rostral-caudal extent of the nucleus. "Cardiac" cells tended to be more rostral than "pulmonary" cells, and both groups of cells were located in the middle of the nucleus. "Laryngeal" cells were located more caudally in the nucleus. This peripheral representation within the vagal nucleus corresponds more closely to the organization found in the mammalian nucleus ambiguus, rather than to the apparent lack of organization found in the mammalian dorsal motor nucleus. Afferents of IX and X entered slightly rostral to the ventral roots of their respective nerves and descended in two tracts. The majority entered the tractus solitarius and descended in a medial position to cervical spinal cord. A portion of the afferents from the vagus nerve crossed the midline in the lower myelencephalon just dorsal to the central canal and ascended a short distance on the contralateral side. Within the solitary tract, vagal afferents were located in a ventrolateral position as they descended to below the obex. Glossopharyngeal afferents filled the remainder of the tract. A smaller portion of afferents from both IX and X did not enter the solitary tract but descended in the spinal tract of V and the dorsolateral funiculus of the spinal cord (Lissauer's tract) to thoracic levels. Afferents of IX also formed a rostral bundle which extended in the solitary tract to the caudal metencephalon.

Thoracic Vagal Ganglion and Referred Craniofacial Pain: a Case Report and Review

“…These involve several nuclei: the para-brachial and Kolliker-Fuse, solitary, dorsal vagus, paratrigeminal (PA5), trigeminal subnucleus caudalis (SC5), raphe magnus, area postrema and medial and lateral reticular nuclei in the medulla oblongata and pons (rostro-ventro-lateral and lateral). The vagus' visceral information is important for maintaining the reflexes conserving homeostatic functions and which are coordinated together with talking, masticatory-deglutitoryrespiratory, pain modulation, cardio-pulmonary, vasopressor, secretomotor and somatomotor mechanism complexes; trigeminal afferents participating in vegetative, gustatory, pneumotaxic and cardio-respiratory centers (Kalia & Mesulman, 1980;Stuesse et al, 1984;Bon et al, 1997;Armstrong & Hopkins, 1998;Saxon & Hopkins, 1998;Ruggiero et al, 2000;Caous et al, 2001;Sato & MomoseSato, 2004;Afifi & Bergman, 2005;Kobayashi et al, 2005). The vagus' afferents mostly reach the solitary nucleus, the rest the vagal dorsal nucleus and PA5 and SC5 nuclei.…”

Gustatory signal processing in the glossopharyngeo-hypoglossal reflex arc of the frog.

“…All the 53 neurons (empty circles) depicted were found to distribute at 0.6-2.2 mm rostral to the obex, 0.3-1.2 mm from the midline, and 0.25 to 1.8 mm in depth from the dorsal surface of the medulla. As seen in the figure, all the neurons distribute approximately within the NTS, the region surrounding the tractus solitarius (TS) and its ventromedial portion (OPDAM et al, 1976;HANAMORI and ISHIKO, 1983b;STUESSE et al, 1984). Neurons which responded to both antidromic stimulation of the XIIth nerve and taste stimulation of the tongue existed within the region caudomedial to the NTS.…”

“…Electrophysiological (KUMAI, 1980;IsHIKo, 1981, 1983a;NAKACHI et at., 1985) and histological (HANAMORI and ISHIKO,1983b;STUESSE et al, 1984) studies on frogs have revealed that a majority of chemical information in the frog IXth nerve is transmitted to the nucleus tractus solitarius (NTS) which, in turn, sends it to the hypoglossal motor nucleus (HMN). The glossopharyngeohypoglossal reflex arc thus should contain at least two neuron pools in the lower brain stem, the NTS and HMN.…”

Control of respiration in fish, amphibians and reptiles

“…They are situated at the bifurcation of the internal and external carotid arteries and innervated by branches of the glossopharyngeal nerve, which projects its afferent fibres to the NTS in the brainstem (48). These receptors are functionally similar to the mammalian carotid bodies, as they also respond to hypercapnia and their discharge can be modulated by sympathetic stimulation (1).…”