Different types of magnetically sensitive cells in the rat pineal gland.

Extracellular recordings from rat pinealocytes reveal different cell responses following experimental changes in the horizontal component of the ambient magnetic field. While two-thirds of the units recorded did not respond at all, one group is activated, the activation continuing after switching off the magnetic stimuli. These cells were not further activated by a second stimulus. Another group comprises cells characterized by a sustained inhibition or excitation, respectively, during magnetic stimulation. These cells could be influenced by a second stimulus. After guinea pigs and homing pigeons the rat is now the third species in which the pineal gland has been shown electrophysiologically to respond to changes of the ambient magnetic field.