PINEAL TRANSPLANTATION TO THE BRAIN OF PINEALECTOMIZED LIZARDS - EFFECTS ON CIRCADIAN-RHYTHMS OF LOCOMOTOR-ACTIVITY

Pinealectomized lizards (Podarcis sicula) whose locomotor rhythms were recorded in constant temperature (29 degrees C) and darkness were sub divided into 2 groups of hosts: Each belonging to the Ist group (exper imentals) received from a donor a pineal gland, and each belonging to the 2nd one (controls) received a piece of cerebellum. Pineal transpla ntation induced drastic changes in the free-running period (tau) of lo comotor rhythms, which were significantly greater than the tau changes induced by cerebellum transplantation. Either application or removal of melatonin implants left the locomotor rhythms of the controls compl etely undisturbed, showing that in absence of melatonin rhythms (pinea lectomy alone abolishes blood-borne melatonin rhythms) melatonin impla nts are ineffective. Melatonin rhythms, however, had to be present in the experimentals, because the circadian system reacts to melatonin im plants by changing tau (as if melatonin rhythms had been suppressed) a nd to removal of the implants by again changing tau (as if melatonin r hythms had been restored).