Pharmacological Research Communications, VoL 12, No. 5, 1980 501 A MASS-FRAMMENTOGRAPHIC APPROACH TO RELEASE STUDIES OF ENDOGENOUS G~BA, GLUTAMIC ACID AND GLUTAMINE "IN VITRO". F. Moroni~ S. Tanganelli~ C. Bianchi~ G. Moneti°and L. Beani~ °Dept.of Pharmacology and Toxicology, University of Florence +Dept.of Pharmacology and ~harmacognosy, University of Ferrara. Introduction The demonstration of a stimulus-induced, Ca 2+ - dependent release of a molecule from presynaptic terminals is one of the criteria used for establishing its possible role as a neurotrans- mitter (Curtis and Johnston, 1974; Werman, 1966). For this reason numerous investigators have studied the depolarization-induced re- lease of radiolabelled amino-acids from brain slices (Katz et al. 1968; Srinivasan et al. 1969; Mulder and Snyder, 1974; Orrego and Miranda, 1976; Nadler et al., 1977; Szerb, 1979}. Since these investigations have been performed by measuring the output of preloaded radioactive materials, the results may be hampered by problems of metabolism, comportamentalization and ex- change. T~erefore we thought it interesting to investigate the ef- fects of appropriate electrical or JK+ stimulation on the release of endogenous amino-acids detected by using a sensitive and specific mass-frammentographic approach. In this paper we will describe pre- liminary observations on the release of GABA, glutamic acid and glutamine from superfused guinea-pig brain slices. Materials and methods Guinea-pigs of both sexes, average weight 400-500 g were use~7 Caudatal slices were prepared and perfused according to Beani et al. (1978). GABA, glutamic acid and glutamine Were measured mass-frammen- tographically , according to Costa et al. (1979), with a few modi- fications. Deuterated internal standards (GABA D 6 0.05 nmoles, glutamate D 5 and glutamine D_ O.10 nmoles dissolved in perchloric acid (0.4 N) were added to t~e collected Derfusion medium. The mixture was load- ed into small columns containing I ml of Dowex 50 x 8, 200-400 mesh in acid form. The columns had been previously washed with 2 ml of 2 N HCI which was followed by water rinses until the eluate reached a neutral pH. The amino-acids were eluted from the resin with 0.7 ml Presented at the Third Italian-Soviet Symposium on Neurotransmitters and Brain Function 0031-69891801050501--051~02,0010 0 1980 The Italian Pl~rmaco/ogical Society