Many sensory organs receive information back from the brain by a nerve supply called efferent innervation, which can modulate the sensory signals carried to the brain by the incoming, or afferent, innervation. The statocyst organs of cephalopod invertebrates (cuttlefish, squid, octopus) are sensors used for control of balance and posture, and have many features remarkably similar to the vestibular parts of the vertebrate inner ear, also used for balance. These statocyst organs receive extensive efferent innervation, and one of the compounds found here is nitric oxide (NO), which is currently of great interest in mammalian nervous systems as a potential neurotransmitter or neuromodulator. This project uses a multidisciplinary approach of physiology, pharmacology, and anatomy to localize and characterize the activity of the enzyme nitric oxide synthase (NOS), its product, NO, and interactions of NO with second messenger systems such as cyclic GMP and cyclic AMP. Results from this model invertebrate system will be important beyond clarifying cephalopod statocyst function, because they will provide a better understanding of evolutionary convergence of equilibrium sense organs, and understanding of mechanisms of action of NO, with broad implications for neuroscience in general.
