The proposed studies are based on data from this laboratory which demonstrate a) that depression of glutamic acid release from synaptosomes is not characteristic of non-neuroleptics but is, instead, specific to neuroleptics; b) that neuroleptics affect glutamine-derived glutamic acid by a direct action on glutaminase and c) that purine agonists potentiate neuroleptics. Based on these and previous findings, the following studies are planned. The first thre studies deal with potential means by which neuroleptics affect glutaminase. Glutaminase will be purified via a standard procedure from several brain areas to serve as the enzyme source for the studies in this section. First, incubation in the presence of increasing concentrations of glutamine will establish normal kinetic constants for the enzyme isolated from each brain area. Then, it will be determined whether these constants are affected by neuroleptics. This study will also establish whether the enzyme isolated from the amygdala is identical to the enzyme isolated from other areas. Secondly, activation of the enzyme via phosphate and intererence with this process by neuroleptics will be studied in a fully deactivated preparation. Third, inhibition of glutaminase via the reaction end products (glutamic acid and ammonia) will be determined both with and without neuroleptics. This will establish whether neuroleptics might act through this mechanism. Three studies of purinergic interactions with neuroleptics are also planned. The first of these will assess whether there is a relationship between the degree to which 2-chloroadenosine depresses glutamic acid release in a given brain area and the degree to which neuroleptics elevate adenosine release. Next, it will be determined whether purinergic agonists affect glutamate release in a stereospecific manner. This will be done to establish which receptor class might be involved in the effects. Finally, it will be established whether purinergic antagonists counteract the effects of neuroleptics on glutamate release. At the completion of these studies, the mechanism by which neuroleptics depress glutaminase activity will be isolated, and the degree to which purinergic mechanisms are involved will have been established. These data may be important in elucidating the mechanism by which neuroleptics produce their antipsychotic effects.
