Distribution of somatostatin-28 (1-12), calcitonin gene-related peptide, and substance P in the squirrel monkey brainstem: an immunocytochemical study.

Using an immunocytochemical technique, we have studied the distribution of fibers and cell bodies containing somatostatin-28 (1-12) [SOM-28 (1-12)], calcitonin gene-related peptide (CGRP), and substance P (SP) in the brainstem of Saimiri sciureus. The distribution of the peptidergic cell bodies was very restricted: perikarya containing SOM-28 (1-12) were only observed in the substantia grisea centralis, while no immunoreactive cell bodies containing CGRP or SP were visualized. Fibers containing SOM-28 (1-12), CGRP, or SP were widely distributed in the brainstem: immunoreactive fibers containing SOM-28 (1-12) showed the most widespread distribution and were the most abundant. The distribution of SOM-28 (1-12)-, CGRP- or SP-immunoreactive fibers was very similar. Colocalization of immunoreactive fibers containing SOM-28 (1-12), CGRP or SP was observed in many brainstem nuclei. A neuroanatomical relationship between CGRP- and SP-immunoreactive fibers was observed, although this relationship was less marked for SOM-28 (1-12) and SP and lower still for SOM-28 (1-12) and CGRP. The widespread distribution of the peptidergic fibers suggests that the studied neuropeptides are involved in many physiological actions.

Mapping of somatostatin-28 (1-12) in the alpaca (Lama pacos) brainstem.

Using an indirect immunoperoxidase technique, we studied the distribution of cell bodies and fibers containing somatostatin-28 (1-12) in the alpaca brainstem. Immunoreactive fibers were widely distributed throughout the whole brainstem: 34 brainstem nuclei/regions showed a high or a moderate density of these fibers. Perikarya containing the peptide were widely distributed throughout the mesencephalon, pons and medulla oblongata. Cell bodies containing somatostatin-28 (1-12) were observed in the lateral and medial divisions of the marginal nucleus of the brachium conjunctivum, reticular formation (mesencephalon, pons and medulla oblongata), inferior colliculus, periaqueductal gray, superior colliculus, pericentral division of the dorsal tegmental nucleus, interpeduncular nucleus, nucleus of the trapezoid body, vestibular nucleus, motor dorsal nucleus of the vagus, nucleus of the solitary tract, nucleus praepositus hypoglossi, and in the substantia nigra. This widespread distribution indicates that somatostatin-28 (1-12) is involved in multiple physiological actions in the alpaca brainstem.

Mapping of tyrosine hydroxylase in the diencephalon of alpaca (Lama pacos) and co-distribution with somatostatin-28 (1-12).

Based on previous work describing the distribution of somatostatin-28 (1-12) in the male alpaca (Lama pacos) diencephalon, and owing to the well known interactions between this peptide and the catecholaminergic system, the aims of this work are (1) to describe the distribution of putative catecholaminergic cell groups in the alpaca diencephalon and (2) to study the possible morphological basis of the interactions between these substances in the diencephalon of the alpaca by using double immunohistochemistry methods. Thus, the distribution of catecholaminergic cell groups in the alpaca diencephalon agrees with that previously described in the diencephalon of other mammalian species of the same order: the A11, A12, A13, A14 and A15d cell groups have been identified; however, we have observed an additional hitherto undescribed cell group containing tyrosine hydroxylase in the medial habenula. In addition, double-labelling procedures did not reveal neurons containing tyrosine hydroxylase and somatostatin, suggesting that the hypothalamic interactions between catecholamines and somatostatin at intra-cellular level must be carried out by a somatostatin molecule other than fragment (1-12). Otherwise, the overlapping distribution patterns of these substances would suggest some interconnections between groups of chemospecific neurons. These results could be the starting point for future studies on hypothalamic functions in alpacas, for example those concerning reproductive control, since other physiological studies have suggested that this species could have different regulatory mechanisms from other mammalian species. Our results support the Manger hypothesis that the same nuclear complement of neural systems exists in the brain of species of the same order.

Mapping of somatostatin-28 (1-12) in the alpaca diencephalon.

Using an immunocytochemical technique, we report for the first time the distribution of immunoreactive cell bodies and fibers containing somatostatin-28 (1-12) in the alpaca diencephalon. Somatostatin-28 (1-12)-immunoreactive cell bodies were only observed in the hypothalamus (lateral hypothalamic area, arcuate nucleus and ventromedial hypothalamic nucleus). However, immunoreactive fibers were widely distributed throughout the thalamus and hypothalamus. A high density of such fibers was observed in the central medial thalamic nucleus, laterodorsal thalamic nucleus, lateral habenular nucleus, mediodorsal thalamic nucleus, paraventricular thalamic nucleus, reuniens thalamic nucleus, rhomboid thalamic nucleus, subparafascicular thalamic nucleus, anterior hypothalamic area, arcuate nucleus, dorsal hypothalamic area, around the fornix, lateral hypothalamic area, lateral mammilary nucleus, posterior hypothalamic nucleus, paraventricular hypothalamic nucleus, suprachiasmatic nucleus, supraoptic hypothalamic nucleus, and in the ventromedial hypothalamic nucleus. The widespread distribution of somatostatin-28 (1-12) in the thalamus and hypothalamus of the alpaca suggests that the neuropeptide could be involved in many physiological actions.