Neural map formation in the mouse olfactory system

In the mouse olfactory system, odorants are detected by ~1,000 different odorant receptors (ORs) produced by olfactory sensory neurons (OSNs). Each OSN expresses only one functional OR species, which is referred to as the “one neuron–one receptor” rule. Furthermore, OSN axons bearing the same OR converge to a specific projection site in the olfactory bulb (OB) forming a glomerular structure, i.e., the “one glomerulus–one receptor” rule. Based on these basic rules, binding signals of odorants detected by OSNs are converted to topographic information of activated glomeruli in the OB. During development, the glomerular map is formed by the combination of two genetically programmed processes: one is OR-independent projection along the dorsal–ventral axis, and the other is OR-dependent projection along the anterior-posterior axis. The map is further refined in an activity-dependent manner during the neonatal period. Here, we summarize recent progress of neural map formation in the mouse olfactory system.     

Pigment formation in sensory cells ofAplysia l

Summary The yellow-brown pigment present in the sensory cells ofAplysia limacina was studied using light and electron microscopy. The ultrastructure, the high carotenoid content and the presence in neurons for which a turnover process has been hypothesized, indicate that these pigments are cytosomes, organelles involved in the production of energy in anaerobiosis.This investigation was conducted at the Zoological Station of Naples.     

Taste perception and coding in the periphery

Recent identification of taste receptors and their downstream signaling molecules, expressed in taste receptor cells, led to the understanding of taste coding in the periphery. Ion channels appear to mediate detection of salty and sour taste. The sensations of sweet, umami and bitter taste are initiated by the interaction of sapid molecules with the G-protein-coupled receptors T1Rs and T2Rs. Mice lacking either PLCβ2 or TRPM5 diminish behavioral and nerve responses to sweet, umami and bitter taste stimuli, suggesting that both receptor families converge on a common signaling pathway in the taste receptor cells. Nevertheless, separate populations of taste cells appear to be uniquely tuned to sweet, umami and bitter taste. Since PLCβ2-deficient mice still respond to sour and salty stimuli, sour and salty taste are perceived independent of bitter, umami and sweet taste. In this review, the recent characterization of the cellular mechanisms underlying taste reception and perception, and of taste coding in the periphery will be discussed. Received 5 March 2006; received after revision 2 May 2006; accepted 10 June 2006     

Harmaline tremor: activity of the interposito-rubral system and of the bulbo-ponto-reticular formation

The effects of tremogenic doses of harmaline have been studied by extracellular unit recordings and 14C 2-deoxyglucose marking in two groups of cats. Harmaline sensitive neurons were found in the lateral reticular nucleus and the nucleus reticularis tegmenti pontis. The nucleus interpositus as well as the red nucleus were also found to be discharging at the tremor frequency, indicating that the cerebello-interposito-rubral system participates in harmaline tremor. In cats with unilateral sections of the inferior cerebellar peduncle, 14C 2-deoxyglucose marking demonstrated that the increased activity previously observed in those structures was a consequence of harmaline acting on the inferior olive.     

Axo-axonic synapses in the main sensory trigeminal nucleus

Résumé Des petites projections, provenant de boutons axoniques, sont émises dans un certain nombre de boutons axoniques adjacents au niveau du principal noyau sensoriel trijumeau.     

Fine structure and function of the sensory pegs on the scorpion pectine

Zusammenfassung Elektronenmikroskopische Untersuchungen der Sensillen auf dem kammförmigen Organ des SkorpionsLeiurus quinquestriatus zeigen einen Bau, welcher einer Reaktion auf mechanische Deformierungen besonders angepasst scheint. Die Funktion dieser Sinnesorgane wäre die Erkennung der Partikelbeschaffenheit des Untergrunds.     

Cholesterol and sterol-like compound in developing chick embryo sensory ganglia

Riassunto Sono stati misurati per via gascromatografica i livelli di colesterolo e di un composto steroidico a struttura finora sconosciuta nei gangli sensitivi di embrione di pollo di 6 fino a 14 giorni di età. I risultati ottenuti mostrano che durante lo sviluppo lo steroide a struttura sconosciuta ha una massima concentrazione a 8–9 giorni per poi decrescere fino a 14 giorni, mentre il colesterolo presenta una tipica curva di accrescimento adS con due punti di flesso, uno a 8 ed uno a 11 giorni.