Response of canine brain loci to intracerebroventricular thyroxine

The effect of intracerebroventricular T4 on certain hypothalamic i.e., POA and VMN and cortical i.e., HPC and CO loci was investigated by recording their electroencepgraphic activity after chronic implantation of cannulae and bipolar electrodes in ten male dogs. Recordings were made for two hours after the microinjection. The predominant pattern of EEG activity was a synchrony of brain waves in all derivations except for POA where biphasic desynchronization-synchronization was observed. Final synchrony suggest refractoriness of these loci to T4 which might be playing a protective role.