And so the two teams joined forces to determine whether the cells Lthi had been studying corresponded to the PKCδ+ and PKCδ− cells Anderson's lab had isolated. In what Anderson refers to as a "sophisticated experiment," the two teams performed electrophysiological recordings while simultaneously turning the PKCδ+ neurons on or off using a genetic method developed by Henry Lester, Caltech's Bren Professor of Biology.
The results of the experiment were "gratifyingly clear," says Anderson. The cells that decreased their activity in the face of fear-inducing stimuli clearly corresponded to the PKCδ+ neurons Anderson's lab had isolated, while those that increased their activity corresponded to the PKCδ− neurons.
"These results supported the hypothesis that PKCδ+ neurons were indeed at the opposite end of the seesaw from the one that the fear signal 'presses down' on, consistent with the finding that PKCδ+ neurons crimp the 'fear hose,'" says Anderson.
The marriage of molecular biology and electrophysiology created by the collaboration between Anderson's and Lthi's laboratories has revealed properties of the fear circuit that could not have been discovered in any other way, Anderson says. "The functional geography of the brain is organized like that of the world," he notes. "It's divided into continents, countries, states, towns and cities, neighborhoods and houses; the houses are analogous to the different types of neurons. Previously, it had only been possible to dissect the amygdala at the level of different towns, or of neighborhoods
|Contact: Jon Weiner|
California Institute of Technology