Grueneberg ganglion neurons respond to cool ambient temperatures

Abstract

The Grueneberg ganglion (GG) - a neuronal cell cluster of unknown function localized to the vestibule of the anterior nasal cavity - is considered as a chemosensory compartment based on the expression of olfactory receptors and the olfactory marker protein. Axonal projection of GG neurons to so-called 'necklace glomeruli' in the olfactory bulb of the brain, which are thought to be important for suckling behaviour in rodent pups, has led to the hypothesis that the GG might be involved in mother/child interactions. To survey potential activation of GG neurons in living animals during the course of mother/child interactions, expression of the activity-dependent gene c-Fos in the GG of neonatal mouse pups was monitored in the presence and absence of the dam. It was found that GG neurons were only activated in the absence of the mother. Moreover, GG activation was independent from olfactory cues as revealed by naris occlusion. Searching for stimuli eliciting GG activity in pups separated from the dam, cool ambient temperatures were found to induce strong c-Fos expression in GG neurons whereas warmer temperatures did not. These coolness-induced responses were only observed in a distinct subset of GG neurons characterized by the expression of the olfactory receptor V2r83. Finally, GG responsiveness to coolness was remarkably reduced in older stages. In summary, these findings suggest that the GG of neonatal mice is activated by cool ambient temperatures to which they are exposed in the absence of their dam, indicating that the GG might function as a thermosensor.

Grueneberg Ganglion Neurons Are Finely Tuned Cold Sensors

“…As GGNs are ensheathed by glial cells and covered with keratinized epithelium Brechbühl et al, 2008;Liu et al, 2009) it has proven impracticable to obtain patch-clamp recordings from these neurons to this point (J. Weiss and F.Z., unpublished observations). As our findings provide direct evidence for a thermosensory role of GGNs they support and extend those of Mamasuew et al (2008) using c-Fos expression. But how can they be reconciled with the results of Brechbühl et al (2008)?…”

“…Thus far, only two studies have addressed this problem. Mamasuew et al (2008) used immediate early gene expression to suggest that the Grueneberg ganglion is activated by cool ambient temperature. By contrast, Brechbühl et al (2008), using cellular Ca 2ϩ imaging, found no evidence for temperature-induced responses in GGNs but were able to activate the cells with an as yet unidentified chemical that they collected during killing of mice with CO 2 .…”

Mouse alarm pheromone shares structural similarity with predator scents

“…Each cell sends out a single axon, and axons fasciculate immediately as they project caudally along the dorsal roof of the nasal cavity to the necklace complex in the olfactory bulb (24-26, 28, 29). The GG displays multimodal properties (21,(30)(31)(32)(33) and starts developing around embryonic day 16. Contrary to the other olfactory subsystems, the GG appears to be complete and functional at birth (24)(25)(26)(27)(28), ensuring immediate AP sensing and increasing chances of survival in the wild.…”

A 3.7 kb Fragment of the MouseScn10aGene Promoter Directs Neural Crest But Not Placodal Lineage EGFP Expression in a Transgenic Animal

“…7G), which was most visible in young pups (Ͻ3 d old). The Grueneberg ganglion, an olfactory organ capable of detecting alarm pheromones and cold temperatures (Mamasuew et al, 2008;Fleischer and Breer, 2010;Schmid et al, 2010), is located within the nasal cavity, and dissection of this ganglion revealed EGFP expression (Fig. 7G, right).…”