Source of corticotropin-releasing hormone-like innervation of the adrenal glands of fetal and postnatal sheep

In pro- and postnatal sheep the irregularly shaped adrenal corticomedullary interface is innervated by corticotropin-releasing hormone (CRH)-like beaded fibers. Since CRH-like staining is also seen in the splanchnic nerves, we examined the intermediolateral sympathetic columns (ISC) of the thoracic (T) spinal cords (segments 5-13) of 12 pre- and postnatal sheep for CRH-like immunocytochemical reactivity and in a subset of fetuses, fluorogold immunoreactivity after fluorogold injection to the left adrenal medulla. All animals had CRH-like immunopositive neurons in the ISC from all thoracic segments. The number of CRH-like positive neurons per thoracic segment did not change either from anterior to posterior within groups nor were there differences between groups. Fluorogold immunopositive neurons occurred in the ISC of all injected animals from T⁵ to T¹³. Upon double immunostaining, some ISC CRH-like immunopositive neurons also demonstrated fluorogold immunopositivity. Taken together, these studies indicate that there are CRH-like immunopositive neurons in the ISC of pre- and postnatal sheep and that some of these CRH-like immunopositive neurons innervate the adrenal medulla.