Inhibition of the noradrenergic induction of pineal N-acetyltransferase by dibutyryl cyclic guanosine monophosphate and by ionophore X-537A.

Utilizing rat pineals in vitro, it can be demonstrated that dibutyryl cyclic GMP and the calcium ionophore X-537A are both able to reversibly inhibit the elevation of pineal N-acetyltransferase induced by the beta-agonists norepinephrine or isoproterenol. These results are discussed in terms of the known hyposensitivy of the pineal gland to overstimulation by beta-agonists.