PI: Sosa IBN-9707091 It is known that growing neurons and their axons can sense their way towards a specific target by 'reading' a variety of guidance cues that they encounter in their terrain along the way. Once the terminal branch of a neuron reaches the area where it is going to 'settle' it needs to establish connections, known as synapses, with certain neurons and not others. The mechanisms by which neuronal terminals ultimately sort themselves out within a maze of thousands of possible interconnections at a specific area are not well understood yet. A phenomenon that plays a role in this sorting out is that of competition between neurons synapsing with a common target cell. The strength of synaptic between neurons is modified when other competing synapses are also present. This phenomenon has been observed in the peripheral and central nervous system of the cockroach will be used as a model to study synaptic competition between sensory neurons that form permanent connections with the same target interneuron. A mutant strain in which the effects of a single additional neuron on a previously formed connection can be assessed will be used to determine if the presence of the additional neuron affects how the points of contact between the sensory neurons and their target are distributed and whether the additional competing neuron is preprogrammed to be weaker or becomes weaker as a result of its timing of arrival relative to other neurons. The investigator will also attempt to mimic the phenomenon of synaptic competition between mammalian neurons grown in culture to try determine specifically what the involved neurons are actually competing for. Results from this project will not only further our understanding of how synapses develop and how the complex circuitry of the brain and spinal cord is ultimately established, but will also be of relevance in understanding recovery of function following injury to the nervous system, since synaptic competition is also observed as neurons rege nerate.
