Somatostatin neurons in the small intestine of the guinea pig: a light and electron microscopic immunocytochemical study combined with nerve lesion experiments by laser irradiation.

Somatostatin-like immunoreactive neurons are present in both the myenteric and the submucous plexuses of the small intestine of the guinea pig. Dense varicosities of immunopositive nerve fibres surround the ganglionic cells, some of which also display somatostatin-like immunoreactivity. Immunoelectron microscopy demonstrated axo-somatic synapse formation between the somatostatin immunoreactive neuronal elements. Nerve lesion experiments using argon laser irradiation showed that most of the somatostatin-like immunoreactive fibres of the myenteric plexus were directed anally, whereas those of the submucous plexus had no directional polarity.