Petroses

The most dramatic phenotype in NRTN knockout mice is a breathing defect due to loss of about half of the neurons in the petrosal ganglia. NRTN can support both dopaminergic neurons and spinal motor neurons in vitro,... 

Other tests that can help determine the etiology include the high-dose dexamethasone suppression test, plasma ACTH test, metyrapone stimulation test, corticotropin-releasing hormone stimulation test or inferior petrosal sinus sampling. 

PAL is one of the best-characterized enzymes of plant secondary metabolism. It converts l-phenylalanine into tran -cinnamate ( -cinnamate) by the tra 5-elimination of ammonia and the pro-StS proton (see Ref. 4 for a full reaction discussion). The enzyme, which requires no cofactor, is a tetramer of 310-340 kDa. A cDNA for PAL was first isolated from Petrose-linum crispum (parsley), and others have subsequently been isolated from numerous species. Often PAL is produced from a multigene family and is present in a variety of isoenzyme forms. 

Rother, D. et al., An active site homology model of phenylalanine ammonia-lyase from Petrose-linum crispum. Eur. J. Biochem., 269, 3065, 2002. 

Figure 1. Diagram of the three cranial nerves and associated sensory ganglia that innervate taste buds. As illustrated, electrical recordings were taken from single neurons in the ganglia. Geniculate ganglion in facial nerve petrosal in glossopharyngeal nodose in vagus.

Figure 2. Taste systems of the rat geniculate (GG) and petrosal (PG) ganglia. Location of receptive fields indicated by a dot on tongue for each neuron studied. Examples are shown of elicited spike discharge for neurons from the six different neural groups identified.

The only other group of neurons responsive exclusively to salts was the rat PG salt unit group (Fig. 3). These units of the petrosal ganglion responded to a variety of Cl salts, not showing the Na,... 

Geniculate Ganglion (Facial Nerve) GG. Petrosal Ganglion (Glossopharyngeal Nerve) PG... 

Present in the rat petrosal ganglion was another set of acid units responsive primarily to certain carboxylic acids. Unlike the cat (7), the rat was unresponsive to some carboxylic acids even though they were in low pH solutions (2). Possibly the same is true for the rat GG acid units which were not investigated in as much detail. PG acid units, unlike all other acid unit groups, responded in a "grouping" discharge fashion. 

The human clearly possesses a facial nerve amino acid system similar to the carnivore (16) and a petrosal system similar to the dog furaneol system (14, 17). The human also possesses a glutamate system, yet undetected in any experimental mammal (18, 19). 

ACTH, Adrenocorticotropic hormone CRH, corticotropin-releasing hormone CT, computed tomography IPS, inferior petrosal sinus MRI, magnetic resonance hnaging. 

CT MRI selective venous sampling for ACTH measurements (inferior petrosal sinus venous to peripheral venous ratios) Adrenal Studies... 

Oldfield EH, Doppman JL, Nieman LK, Chrousos GP, Miller DL, Katz DA, et al. Petrosal sinus sampling with and without corticotropin-releasing hormone for the differential diagnosis of Cushing s syndrome. N Engl J Med 1991 325 897-905. 

List of Abbreviations CA, carbonic anhydrase Hx, hypoxia IbTX, iberiotoxin PGN, Petrosal ganglion neurons RTN, retrotrapezoid VLM, ventrolateral medullary area... 

Using the same coculture techniques, glomus cells with petrosal ganglion cells (PGN) and recording from the PGN neurons, it was shown that PGN cells and their terminals responded to hypoxia and CO2/PH and not the PGN cells alone (Zhong et al., 1997 Prasad et al., 2001 Zhang and Nurse, 2004). This means that neurotransmitters released from the glomus cells excited the PGN cells. These transmitters consisted of ATP and ACh. Similar results were obtained by Varas et al. (2003). Recorded intracellularly from identified PGN functionally connected with the carotid body (CB) in vitro, and which responded to CB stimulation by stop... 

Varas R, Alcayaga J, Iturriaga R 2003. Carotid chemosensory neurons in the petrosal ganglia are excited by ACh and ATP. Adv Exp Med Biol 536 321-326. 

Zhang M, Nurse CA. 2004. CO2/PH chemosensory signaling in co-cultures of rat carotid body receptors and petrosal neurons role of ATP and ACh. J Neurophysiol 92 3433-3445. 

Zhong H, Zhang M, Nurse CA. 1997. Synapse formation and hypoxic signalling in co-cultures of rat petrosal neurones and carotid body type 1 cells. J Physiol 503 599-612. 

Wiggam Ml, Heaney AP, Mcllrath EM, et al. Bilateral inferior petrosal sinus sampling in the differential diagnosis of adrenocorticotropin-dependent Cushing s syndrome a comparison with other diagnostic tests. J Clin Endocrinol Metab 2000 85 1525-1532. 

Fig. 148. Compartmentation in AChE-stained transverse sections of the flocculus, the ventral paraflocculus and the petrosal lobule and the caudal hemisphere of Saimiri sciureus. Note AChE stained borders of the compartments and the differential staining in the molecular layer AChE-positive cells of the basal interstitial nucleus of Langer are located along the borders of the compartments C2, 1 and 2 in (D) and (E). Group y is located within the floccular peduncle in (E), ANS = ansiform lobule br.p = brachium pontis c.rest = restiform body Cl-3 = C21-3 compartments D = dentate nucleus Dl,2 = Dl,2 compartments F = fastgial nucleus fis.post.lat = posterolateral fissure FLOC = flocculus lA = anterior interposed nucleus IP = posterior interposed nucleus Ib.petr = petrosal lobule PFLD = dorsal paraflocculus PFLV = ventral paraflocculus. Courtesy of Dr. D.T. Hess.

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