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.