Effects of superior cervical preganglionectomy on nerve vesicles and synaptic ribbons in the cat pineal gland.

Previous studies have shown that bilateral preganglionectomy of the superior cervical ganglia (SCGp) modifies the nerve vesicles and synaptic ribbons in the cat pineal gland. In the present study the nerve vesicles (NV) and synaptic ribbons (SR) were analyzed morphometrically after chronic preganglionectomy of the pineal sympathetic nerve fibers. It was shown that bilateral sympathectomy of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and, on the other hand, modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after chronic preganglionectomy of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.