SGER: Effects of Thyroxine on Peripheral Imprinting

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WPC_ 2 B V P Z Courier 10cpi ? x x x , k x 6 X @ 8 ; X @ HP LaserJet III HPLASEII.PRS x @ , t 0 OpX @ 2 Z L ! #| x Canon LBP-8III (Letterhead) CALB8IAD.PRS x @ 0 jFX @ Courier 10cpi Courier 10cpi Bold 2 X . ? x x x , l x 6 X @ 8 ; X @ l ? x x x , x ` w ; X ' 9 N ( ı 5 6N E 2 D u | u | t D 5 t$ D E =& t =^ u y r= u t " s r 9320702 Roberts Salmons are well known for their ability to return to the stream in which they were born. The sensory basis for this remarkable behavior is olfactory: during a sensitive developmental period (smolt transformation), salmon imprint to distinctive homestream odors, and adults later use this odorant memory as a migratory cue to guide them back from the open ocean to their natal streams. How salmon imprint to homestream odors has remained an important but perplexing puzzle for over forty years. Proponents of olfactory imprinting have assumed that the olfactory memory for the home stream resides in the central nervous system. Dr. Roberts, however, proposes that olfactory memory is actually retained in the olfactory receptor cells themselves. The basis for his theory rests on two important findings. First, surges in plasma thyroxine levels mediate smolting, and second, olfactory imprinting coincides with this developmental metamorphosis. This small grant for exploratory research enables Dr. Roberts to use state of the art electrophysiological and neuroanatomical techniques to determine whether there are thyroxine induced change s in olfactory receptor neurons to specific odors. This basic research will have direct benefits to Pacific salmon by providing insight into how olfactory imprinting might be artificially manipulated. If thyroxine hormone can influence the ability of fish to imprint during a wider time frame than smolting, this finding could markedly advance conservation efforts aimed at transporting rapidly diminishing endangered salmon runs to healthier river systems. ***