“…At present, the amino acid glutamate (Molna´r et al, unpublished), the neuropeptides (Gardner & Cashin, 1975;Gardner, 1981;Curry et al, 1989;Fuji et al, 1989;Al-Yousuf, 1992;Lubics et al, 1997;Regl} odi et al, 1997;Molna´r et al, 2001), the gaseous neurotransmitter nitric oxide (Zsombok et al, 1999;Kitamura et al, 2001;Molna´r et al, 2001;, the monoamines (Rude, 1966;Ehinger & Myhrberg, 1971;Bieger & Hornykiewicz, 1972;Gardner & Cashin, 1975;Gardner, 1981;Spo¨rhase-Eichmann et al, 1987a, b, 1998 and the inhibitory neurotransmitter camino butyric acid (GABA) (Telkes et al, 1996;Spo¨rhase-Eichmann et al, 1997;Molna´r et al, 2000Molna´r et al, , 2001 have been identified in earthworms. GABA, which is thought to be the major inhibitory neurotransmitter in both invertebrates and vertebrates (Sepherd, 1994), acts as neurotransmitter in earthworms, having been identified in a population of primary sensory cells (Spo¨rhase-Eichmann et al, 1997;Solt et al, 2001) and in some motoneurons (Telkes et al, 1996).…”