Development of sympathetic neurones in vivo: an investigation of the possible role of glucocorticosteroids in regulating transmitter type.

In vivo the majority of sympathetic neurones are adrenergic, whereas in vitro they can become cholinergic. This atypical cholinergic development can be suppressed by addition of a glucocorticoid to the culture medium (McLennan, Hill and Hendry, 1980). In this paper we have investigated the possibility that glucocorticoids influence the choice of sympathetic transmitter type in vivo. Reduction in circulatory glucocorticoids by adrenalectomy of 2-day-old rat pups did not result in increased cholinergic development in their superior cervical ganglia. Furthermore, administration of exogenous corticosterone to increase circulatory glucocorticoids in young rats did not prevent the developmental switch in transmitter type of the sympathetic innervation of the sweat gland from adrenergic to cholinergic. It is concluded that the developmental regulation of sympathetic transmitter type in vitro may not be analogous to that in vivo.