Pseudorabies virus and the functional architecture of the circadian timingsystem

Transneuronal tracing of neuronal circuitry with neurotropic viruses has pr ovided valuable insights in the way in which the nervous system imposes tem poral organization on physiological processes and behavior. The swine alpha herpes virus known as pseudorabies virus, or PRV, has been particularly us eful in this regard. Early studies identified attenuated mutants with selec tive tropism for visual circuitry involved in circadian regulation, and sub sequent experiments employing this virus have provided considerable insight into the polysynaptic organization of the suprachiasmatic nuclei and assoc iated circuitry. This literature, which has emerged during the past decade, is the subject of this mini review.