TYROSINE-HYDROXYLASE ACTIVITY IN PERIPHERALLY DENERVATED RAT PINEAL-GLAND

The presence of tyrosine hydroxylase (TH) in the rat pineal gland was studied using a combination of immunochemical and biochemical methods. In superior cervical ganglionectomized (SCGx) animals and in isolated pineals incubated for 72 h, both TH immunoreactive (TH-IR) fibers and TH biochemical activity were still present but reduced. Conversely, i n dispersed pinealocytes incubated for only 24 h we were unable to det ect either TH activity or TH-positive cells. Since in the pineal gland of intact rats total 3-methoxy-4-hydroxy phenylglycol (MHPG) was unde tectable, and only traces of norepinephrine (NE) were present in the p ineal of ganglionectomized animals, the results suggest a central pine alopetal catecholaminergic pathway which could use dopamine as a neuro transmitter.