Morphological Relationships between the Cholinergic and Somatostatin-28(1-12) Systems in the Alpaca (Lama pacos) Brainstem

Abstract

In the alpaca brainstem, the distribution of the cholinergic system by the immunohistochemical detection of the enzyme choline acetyltransferase (ChAT) has been described, and its relationship with the distribution of somatostatin-28(1-12) is analyzed by double-immunostaining techniques. Overlapping distribution patterns for both substances were observed in many brainstem regions, suggesting that interactions between them may occur in the reticular formation, nucleus ambiguus or laterodorsal tegmental nucleus. Colocalization of the two substances in the same cell bodies was only observed in restricted areas, such as the nucleus of the solitary tract, reticular formation and nucleus ambiguus. In addition, in several regions, an apparent high innervation of the peptidergic fibers on cholinergic neurons has been observed. The results suggest that chemospecific interactions could be crucial for the control of specific cardiorespiratory and/or digestive functions in alpacas. These interactions may represent brain-adaptive mechanisms to particular environments and have a potential therapeutic use in respiratory disorders.