The effects of intraventricularly administered GABA and picrotoxin and their interactions on somato-vegetative reflexes in cats.

The effects of intraventricularly (third, fourth and lateral cerebral ventricles) applied GABA and picrotoxin on blood pressure and reflexogenic hypertension and nictitating membrane contractions after central sciatic nerve stimulation were studied in lightly anaesthetized cats. The interactions between both substances were also studied. It was shown that picrotoxin caused a strong elevation of blood pressure and a long lasting contraction of the nictitating membrane when infused into each part of the cerebral ventricular system. These effects of picrotoxin were antagonized by GABA. GABA inhibited the reflexogenic hypertension when given into the fourth ventricle and the reflexogenic nictitating membrane contractions given into the third and fourth ventricles. Picrotoxin antagonized the inhibitory effects of GABA on the reflexogenic nictitating membrane contractions. It is concluded that in the central regulation of some somato-vegetative reflexes the GABA-ergic transmitter system takes part.