Maj J, Pawlowski L, Sarnek J.
“The Role of Brain 5-Hydroxytryptamine in the Central Action of L-DOPA”.
. We observed previously (Maj, Grabowska, and Mogilnicka, 1971; Maj and Pawyowski, 1973) that L-DOPA given to rats together with an extracerebral decarboxylase inhibitor, Ro 4-4602, produced (1 ) a depression of locomotor activity if the dose of L-DOPA was low and the activity was measured shortly after-the administration of the amino acid, and (2)a fall in body-temperature. The last effect was not influenced by spiroperidol or
pimozide and was antagonized by p-chilorophenylalanine (Maj and Pawfowski, 1973). L'-DOPA following extracerebral decarboxylase inhibition induces in i rats a decrease in brain 5-hydroxytry.ptamine (5-HT) and an increase in brain 5 - hydroxyindoleacetic acid (5-HIAA) caused mainly by the displacement of endogenous 5 - HT from its stores (Bartholini,-Da Prada, and Pletscher, 1968; Butcher and Engel, 1969; Ng,. Chase, and Colburn,1970). If this is true, the inflow of 5-HT to its receptor should be increased. Thus we were interested in investigating whether the hypothermia and the depression of locomotor activity observed after L-DOPA might be related to its 5-HT displacing action. To this end we decided to study the interaction between L-DOPA and LSD, which according to many literature data may inhibit the.release of 5-HT (e.g.,Freedman and Giarman, 1962; Chase, Breese, and Kopin, 1967, Diaz,Ngai, and Costa, 1968)