Innervation of the rat pineal gland by nerve fibres originating in the sphenopalatine, otic and trigeminal ganglia. A retrograde in vivo neuronal tracing study.

The innervation of the rat pineal gland from the sphenopalatine, otic, superior cervical and trigeminal ganglia was investigated in animals by use of in vivo retrograde tracings. A solution of 2% Fluorogold was iontophoretically injected into the superficial pineal gland in a series of Wistar rats. After a survival time of 4-10 days, the animals were fixed by perfusion and the brains, sphenopalatine, otic, superior cervical and trigeminal ganglia were investigated with a fluorescence microscope. Many retrogradely labelled perikarya were found in the superior cervical ganglia, but a smaller number of neurones were also labelled in the sphenopalatine, otic and trigeminal ganglia. Injections of the tracer into the subarachnoidal space were used as the control for unspecific uptake and transport of the tracer. The input to the pineal gland from the parasympathetic sphenopalatine and otic ganglia might be involved in the regulation of the annual rhythms of the pineal gland. The projections from the sensory trigeminal ganglion could be involved in the control of the blood flow of the gland.