9728551 Kravitz Serotonin has been linked to aggression in a wide and diverse range of species, including man. In vertebrates, lowered levels of this amine, possibly coupled with elevated levels of norepinephrine, have been linked to a particular kind of impulsive violence. While great interest is centered on this research, it is difficult in vertebrate systems, because of the large number of neuronal elements involved, to link amines and aggression at the level of single neurons and the precise changes taking place in the nervous system accompanying violent behavior. In invertebrate systems, with their limited numbers of large identifiable neurons, the analysis of complex behavioral processes, like aggression, can be brought to the level of the precise cells thought to be essential for the behavior. This application continues our studies exploring the function of identified single nerve cells from the lobster central nervous system (cns) that contain and utilize the amines serotonin and octopamine (the invertebrate equivalent of norepinephrine). We believe that these two amines have opposing actions on at least the postural component important in agonistic (fighting) behavior in lobsters. The serotonin cells that are the focus of our studies are neurosecretory cells. These cells release serotonin at two sites: (i) within the central nervous system, where it influences pathways having to do with posture and escape; and (ii) directly into the haemolymph (blood) of the lobster, where the amine changes the ways that muscles and sensory neurons function for prolonged periods of time. Within the cns, much in the same way that dimmer switches work on electrical circuits, the serotonin cells function as "gain-setters" that make particular pathways function better or worse for lengthy periods of time. The present studies will continue our investig ations of these interesting neurons, asking how they are activated, and will begin studies aimed at asking whether these serotonin-containing neurons show any changes in functioning as a long-term consequence of changes in social status. With the octopamine neurosecretory cells we plan studies aimed at defining their physiological roles, learning how they are activated, asking how and where they interact with the corresponding sets of serotonin-containing neurons, and asking whether a subset of these cells that selectively innervate the claws, serve any direct role in the switch to subordinate behavior seen when animals lose one of their large claws. The emphasis in all of our studies is on understanding, at a neuronal level, the short-and long-term consequences of social interactions between animals. With its well studied biochemistry, physiology, anatomy and behavior, the lobster model we are examining, offers many advantages in addressing such issues.
