Pharmacological tools for the study of central glutamatergic neurotransmission in insects

LOCATELLI F; MUELLER U

Berlin, Alemania

Congreso; Berliner Neuroscience Forum, Berlin Alemania 2004.; 2004

Pharmacological tools for the study of central glutamatergic neurotransmission in insects Fernando Locatelli & Uli Müller Institut für Neurobiologie, Freie Universität, Berlin Although a number of immunohistochemical and electrophysiological studies have demonstrated the presence of glutamatergic synapses in the insects CNS, the role of glutamate in behavior and learning in insects has been seldom studied. The cause for this, is probably that insect glutamate receptors have different pharmacological properties than mammalian ones and the classical pharmacological tools used in mammals have low or no effect in insects. On an attempt to study the role of glutamatergic neurotransmission in learning and memory in the honeybee, we observed that the enzymes involved in glutamate re-uptake are highly conserved between mammals and the honeybee. Assuming that drugs used in mammals to manipulate these enzymes should have similar effects in insects, we made a screening of drugs that could affect glutamate levels in CNS of insects. With this purpose we developed an ELISA technique that enables us to measure after drug treatment not only glutamate but also GABA levels, which constitutes the major inhibitory neurotransmitter in insect brain. Drugs tested constituted inhibitors of: a) plasma-membrane glutamate transporters, which are directly involved in removing glutamate from the synaptic cleft; b) the enzyme glutamine-synthetase, which converts glutamate into glutamine in glia cells and constitutes a critical step in glutamate re-uptake; c) vesicular glutamate transporters, which are involved in re-filling of synaptic vesicles. First results demonstrate that while some of the used drugs are effective in changing glutamate levels in the insect brain, effects were also observed in GABA levels. These effects simultaneously observed in excitatory and inhibitory transmission shouldn?t be precluded in the analysis of further behavioral studies and consider for critical analysis of previous reports. Supported by: Fundación Antorchas and SFB-515 (DFG)