Developmental changes in the neurotransmitter properties of dissociated sympathetic neurons: a cytochemical study of the effects of medium

Abstract

Sympathetic principal neurons were dissociated from the superior cervical ganglia of newborn rats and grown in several culture conditions shown previously to affect the transmitter status of the neurons. In three of these conditions the neurons are known to develop adrenergic functions over a 3- to 4-week period; in a fourth condition, they develop predominantly cholinergic functions. In this ultrastructural study, the transmitter status of the neurons during development in the several different media was examined after permanganate fixation which causes a granular precipitate in synaptic vesicles containing norepinephrine (small granular vesicles or SGV). It was found that as early as 4 days after plating, synapses and varicosities were present. In all four conditions, all of the terminals contained numerous SGV, indicating that the neurons both synthesize and store norepinephrine. Under “adrenergic” growth conditions, the terminals remained adrenergic in appearance during further development. Under “cholinergic” conditions, terminals of cholinergic appearance were present as early as 7 days and their incidence increased with time. Although the cholinergic terminals contained little or no endogenous norepinephrine, many were initially able to take up and store exogenous catecholamine. These results indicate that the dissociated sympathetic neurons of newborn rats which survive in culture acquired adrenergic transmitter functions early. Under “cholinergic” culture conditions, the neurons lose the ability to synthesize detectable quantities of norepinephrine; the ability to take up and store detectable quantities of exogenous catecholamines disappears more slowly.