Visual intracortical and transthalamic pathways carry distinct information to cortical areas.

Sensory processing involves information flow between neocortical areas, assumed to rely on direct intracortical projections. However, cortical areas may also communicate indirectly via higher-order nuclei in the thalamus, such as the pulvinar or lateral posterior nucleus (LP) in the visual system of rodents. The fine-scale organization and function of these cortico-thalamo-cortical pathways remains unclear. We find that responses of mouse LP neurons projecting to higher visual areas likely derive from feedforward input from primary visual cortex (V1) combined with information from many cortical and subcortical areas, including superior colliculus. Signals from LP projections to different higher visual areas are tuned to specific features of visual stimuli and their locomotor context, distinct from the signals carried by direct intracortical projections from V1. Thus, visual transthalamic pathways are functionally specific to their cortical target, different from feedforward cortical pathways, and combine information from multiple brain regions, linking sensory signals with behavioral context

Glycolytic metabolite methylglyoxal inhibits cold and menthol activation of the transient receptor potential melastatin type 8 channel.

Methylglyoxal (MG) is a reactive dicarbonyl compound involved in protein modifications linked to diabetes mellitus. The plasma level of MG is elevated in diabetic patients, particularly those with painful diabetic neuropathy. Diabetic neuropathy is often associated with spontaneous pain and altered thermal perception. This study assesses effects of MG on TRPM8, an ion channel involved in innocuous cold sensing and cold allodynia and also in cold-mediated analgesia. Acute treatment with MG inhibited the activation of recombinant rat and human transient receptor potential melastatin type 8 (TRPM8) by cold and chemical agonists. A similar effect was observed when native TRPM8 was investigated in cultured rat dorsal root ganglion (DRG) neurons. DRG neurons treated with MG for 16-24 hr displayed a significant reduction in the fraction of cold- and menthol-sensitive neurons, most likely expressing TRPM8. The fraction of allyl isothiocyanate-sensitive neurons was also reduced, and the coexpression among different neuronal populations was affected. The same prolonged exposure to MG significantly reduced the expression of TRPM8 at the mRNA level. Overall, our data provide evidence for decreased activity and expression level of TRPM8 in the presence of MG, which may be linked to some of the alterations in pain and temperature sensing reported by diabetic patients. © 2015 Wiley Periodicals, Inc