On Mon, 11 Mar 2002, David Epstein wrote: > >From the current issue of Nature. > > http://www.nature.com/nature/links/020307/020307-1.html > Neurobiology: Cold and menthol receptor > > Natural products that mimic sensations of hot or cold are key to > understanding how the nervous system detects temperature. Capsaicin > (from chili peppers) evokes burning paincy by activating an ion > channel that also responds to heat. This week, cloning of a menthol > receptor explains the icy-cool sensation of mint: the receptor is > also activated by cold. Similarities between capsaicin and menthol > receptors suggest that sensory nerve endings use a common molecular > mechanism to detect hot and cold. >
I'm struggling with how new data such as this impacts on older ideas of "specificity theory", that one receptor mediates one sensation, as in von Frey's claim that the free nerve endings are the specific receptors for pain. One difference seems to be that the "receptors" of this kind of research are on a much smaller scale than the old style encapsulated and bare nerve endings of earlier theories. The new receptors are at the molecular rather than light microscope level, and presumably one nerve ending could have a whole set of different such molecular receptors on it. Thus, one could have specificity at the molecular level, and still have a lack of specificity for the neuron. No one seems to be discussing this 'though. This may be because neurophysiologists are reluctant to give up specificity, despite its frequent failures. The output from axons carrying this information into the nervous system is only weakly modality-specific. Many neurons that respond to cold, for example, also respond to warm, to pain, to pressure, etc. This is understandable if there are different specific molecular receptors on the nerve ending. The research does show specificity, but it then feeds into generality. How does the brain sort the signals out? -Stephen ------------------------------------------------------------------------ Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470 Department of Psychology fax: (819) 822-9661 Bishop's University e-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy Check out TIPS listserv for teachers of psychology at: http://www.frostburg.edu/dept/psyc/southerly/tips/ ------------------------------------------------------------------------ --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
