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At least 1,387 records · Page 77Linked to original sources
PubMed1991

The olfactory system, not the terminal nerve, functions as the primary chemosensory pathway mediating responses to sex pheromones in male goldfish.

Studies of the neural mechanisms underlying responsiveness to sex pheromones in male goldfish suggest that, contrary to a currently popular hypothesis, the olfactory system (cranial nerve 1), and not the terminal nerve (cranial nerve 0), mediates chemosensory responses to pheromones. When the olfactory epithelium of male goldfish was exposed to two identified sex pheromones, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one and a mixture of prostaglandin F2 alpha and its metabolite 15-keto-prostaglandin F2 alpha, the spontaneous activity of olfactory neurons located in the medical portion of the olfactory bulb changed, while activity of terminal nerve cell bodies did not. A variety of other synthetic and natural odors also failed to alter the activity of terminal nerve cell bodies as did visual, magnetic, thermal, and auditory cues. Terminal nerve activity was, however, inhibited by tactile stimulation, suggesting that this system may have a modulatory role associated with the physical interactions that characterize goldfish spawning behavior.

Animals↗
PubMed1992

Effects of transections to the vomeronasal nerves or to the main olfactory bulbs on the initiation and long-term retention of maternal behavior in primiparous rats.

While the onset of maternal behavior at parturition is mediated by hormones, the maintenance of maternal behavior during the first few postpartum weeks depends on experiences acquired while the dam interacts with pups (Rosenblatt, 1990). In fact, if female rats are permitted as little as 2 h or maternal experience within 36 h after Cesarean delivery, they exhibit heightened maternal behavior during maternal induction tests 10 days later; in contrast, dams separated from young at the time of Cesarean delivery and not permitted a maternal experience fail to respond maternally in tests 10 days later (Orpen & Fleming, 1987). In this study we investigated the role of chemosensory input through the vomeronasal and main olfactory systems in this maternal experience effect. Six groups of primiparous females were tested for maternal behavior to foster pups presented 9-10 days after Cesarean delivery: three groups were permitted to interact with pups for a 2-h period 36 h after Cesarean delivery; and three groups were separated from pups until testing and were given no maternal experience. Within each experience condition, one group sustained bilateral section of the vomeronasal nerves, one sustained bilateral coronal cuts through the midsection of the main olfactory bulbs, and one group sustained small medial olfactory bulb cuts. The results showed that animals sustaining vomeronasal or olfactory transections, regardless of experience condition, exhibited significantly reduced latencies to maternal behavior in maternal induction tests. However, these chemosensory disruptions did not prevent an additional facilitation of maternal behavior produced by a prior maternal experience.

Animals↗
PubMed2007

Transplanted Schwann cells, not olfactory ensheathing cells, myelinate optic nerve fibres.

In a previous study we found that olfactory ensheathing cells transplanted into complete retrobulbar transections of the rat optic nerve mediated regeneration of severed retinal ganglion cell axons through the graft region. Although the regenerating axons were ensheathed by the transplanted cells, none of the regenerating axons became myelinated by either central or peripheral type myelin. In the present study we used the same operative procedure but transplanted Schwann cells instead of olfactory ensheathing cells. As with the olfactory ensheathing cell transplants the Schwann cells transplants also induced regeneration of the severed retinal ganglion cell axons into the graft region. In contrast to the situation with the olfactory ensheathing cell transplants, however, a considerable number of the regenerating axons became myelinated by peripheral type myelin produced by the transplanted Schwann cells. This observation identifies a further distinction between these two cell types which are phenotypically similar in many ways, but which have been shown to have major functional differences with regard to regeneration in spinal cord lesions.

Animals↗
PubMed1993

Glial cells in the nerve fiber layer of the main olfactory bulb of embryonic and adult mammals.

This article provides a detailed description of the glial cell types in the nerve fiber layer of the main olfactory bulb during embryonic development, in adult mammals, and at the nerve entry zone of the first cranial nerve. In adult mammals, the glial cell types of the olfactory nerve fiber layer include intrafascicular ensheathing cells, which have the exclusive role of ensheathing the olfactory axons in both the PNS and CNS, and interfascicular astrocytes, which occupy the spaces between adjacent olfactory fascicles. The ensheathing cells are particularly interesting because they possess a mixture of Schwann cell and astrocytic phenotypic features, are more likely to be of placodal than of CNS origin, and have the exclusive role of forming the glia limitans at the PNS-CNS transitional zone. It is proposed that one important function of ensheathing cells is to modulate the growth of olfactory axons within the CNS; this modulation is probably mediated by selective cell adhesion molecules, extracellular matrix molecules, and chemotropic agents.

Animals↗
PubMed1997

Functional MR imaging during odor stimulation: preliminary data.

PURPOSE: To determine the locations and extent of activation in areas of the brain at functional magnetic resonance (MR) imaging with olfactory stimulation and to determine whether accommodation or amplification of brain activation occurs with sequential olfactory stimulation. MATERIALS AND METHODS: Five adult men with normal senses of smell underwent multisection, gradient-echo, echo-planar imaging according to a blood-oxygen-level-dependent experimental paradigm. Odorants that nearly exclusively stimulate the olfactory system and odorants that stimulate the olfactory and trigeminal nerves were compared by using repetitive imaging procedures. RESULTS: Activation with olfactory nerve-mediated odorants was demonstrated in the orbitofrontal cortex (Brodmann area 11) with a right-sided predominance. Mild cerebellar stimulation was also observed. With repeated testing, overall activation with olfactory nerve-mediated odorants declined. Odorants that also stimulated the trigeminal nerve produced additional cingulate, temporal, cerebellar, and occipital activation. Activation with combined trigeminal and olfactory system odors increased more than sixfold with repeated testing. CONCLUSION: Olfactory nerve-mediated and combined olfactory and trigeminal nerve-mediated odorants activate different regions of the brain. Orbitofrontal stimulation spreads to all parts of the brain when a trigeminal component is added. Habituation (deactivation) occurs with repeated testing of olfactory nerve-mediated odorants, while, paradoxically, activation increases with repeated exposure to odors that also stimulate the trigeminal nerve.

Adult↗
PubMed1990

Histochemical demonstration of mercury in the olfactory system of salmon (Salmo salar L.) following treatments with dietary methylmercuric chloride and dissolved mercuric chloride.

The deposition of organic and inorganic mercury compounds was studied histochemically in the salmon (Salmo salar L.) olfactory system. One group of salmon was given fodder pellets containing methylmercuric chloride (CH3HgCl, 99 micrograms Hg/g) for 4 weeks. Other groups of fish were exposed to dissolved mercuric chloride (HgCl2, 270 micrograms Hg/liter) for 2, 6, and 12 hr, respectively. In both series of experiments, the radioisotope 203Hg was included in order to determine the accumulation of mercury in the olfactory system. Gamma-spectrometry showed that both mercury compounds accumulated in the olfactory rosettes and their nerves. Tissue sections from the rosettes and olfactory nerves were subjected to autometallographic silver enhancement, thereby rendering mercury deposits visible for light and electron microscopy. Microscopic analysis demonstrated an intense and comprehensive Hg deposition in the axons and Schwann cells of both methylmercury- and inorganic mercury-exposed fish. On the other hand, the two mercury compounds showed different staining patterns in the sensory epithelium. The silver grains evoked by methylmercury were localized predominantly in lysosome-like inclusions within the receptor cells, while those produced by HgCl2 exposure were situated mainly along the borders of neighboring cells. The present findings that organic and inorganic mercury compounds were deposited in the olfactory system along its whole length, from the receptor cell apices to the brain, support the electrophysiological results presented elsewhere (Baatrup et al., 1990, Ecotoxicol. Environ. Safety 20, 269-276).

Administration, Oral↗