Immunohistochemical study of the brainstem cholinergic system in the alpaca (<em>Lama pacos</em>) and colocalization with CGRP

Abstract

Several cholinergic regions have been detected in the brainstem of mammals. In general, these regions are constant among different species, and the nuclear complement is maintained in animals belonging to the same order. The cholinergic system of the brainstem has been partially described in Cetartiodactyla, except for the medulla oblongata. In this work carried out in the alpaca, the description of the cholinergic regions in this order is completed by the immunohistochemical detection of the enzyme choline acetyltransferase (ChAT). In addition, using double immunostaining techniques, the relationship between the cholinergic system and the distribution of calcitonin gene-related peptide (CGRP) previously described is analysed. Although these two substances are found in several brainstem regions, the coexistence in the same cell bodies was observed only in the laterodorsal tegmental nucleus, the nucleus ambiguus and the reticular formation. These results suggest that the interaction between ChAT and CGRP may be important in the regulation of voluntary movements, the control of rapid eye movement sleep and states of wakefulness as well as in reward mechanisms. Comparing the present results with others previously obtained by our group regarding the catecholaminergic system in the alpaca brainstem, it seems that CGRP may be more functionally related to the latter system than to the cholinergic system.

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

“…These studies complement previous works regarding the mapping of neuro-modulatory systems in the brain of Artiodactyla and confirm that the nuclear complement of neurotransmitters, such as acetylcholine or catecholamines, detected in the alpaca brainstem and diencephalon Anatomia 2022, 1 55 was similar to that found in other members of the same order, and this finding supports Manger's hypothesis [13]. In addition, the distribution of some neuropeptides has been studied in the alpaca brainstem [6][7][8][9]12] and diencephalon [10,11]. Moreover, the morphological relationship between neuropeptides and neurotransmitters has been reported, and double-immunolabeling for tyrosine hydroxylase, which is the rate-limiting enzyme of the catecholaminergic synthesis, and somatostatin-28(1-12) (Som-28 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)) has been carried out in the diencephalon of the alpaca [11].…”

“…Alpacas are important animals for the economy of numerous South American countries due to the excellent quality of their wool, and in this sense, numerous studies focused on their maintenance and reproductive cycles have been performed [6,7]. The members of the Camelidae family have specific morphological characteristics, such as long necks and seven cervical vertebrae, and moreover alpacas can live at sea level and at 5000 m above sea level [6][7][8][9][10][11][12]. These characteristics suggest the existence of important and unique adaptation mechanisms, mainly related to cardiovascular and respiratory mechanisms, which are controlled by the central nervous system, specifically brainstem centers.…”

“…Since all these physiological functions are regulated by neuroactive substances, several studies have reported the distributions of different classical neurotransmitters and neuropeptides by means of immunohistochemical methods in the alpaca brain [6][7][8][9][10][11][12]. These studies complement previous works regarding the mapping of neuro-modulatory systems in the brain of Artiodactyla and confirm that the nuclear complement of neurotransmitters, such as acetylcholine or catecholamines, detected in the alpaca brainstem and diencephalon Anatomia 2022, 1 55 was similar to that found in other members of the same order, and this finding supports Manger's hypothesis [13].…”

“…In addition, the distribution of some neuropeptides has been studied in the alpaca brainstem [6][7][8][9]12] and diencephalon [10,11]. Moreover, the morphological relationship between neuropeptides and neurotransmitters has been reported, and double-immunolabeling for tyrosine hydroxylase, which is the rate-limiting enzyme of the catecholaminergic synthesis, and somatostatin-28(1-12) (Som-28 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)) has been carried out in the diencephalon of the alpaca [11]. In the brainstem of this species, a double-labeling for choline acetyl transferase (ChAT, a marker for the cholinergic system) and calcitonin gene-related peptide (CGRP), as well as for CGRP and tyrosine hydroxylase [9,12], has been described.…”

“…Moreover, the morphological relationship between neuropeptides and neurotransmitters has been reported, and double-immunolabeling for tyrosine hydroxylase, which is the rate-limiting enzyme of the catecholaminergic synthesis, and somatostatin-28(1-12) (Som-28 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)) has been carried out in the diencephalon of the alpaca [11]. In the brainstem of this species, a double-labeling for choline acetyl transferase (ChAT, a marker for the cholinergic system) and calcitonin gene-related peptide (CGRP), as well as for CGRP and tyrosine hydroxylase [9,12], has been described. According to the distribution of double-labeled perikarya, the results observed in the brainstem in these studies suggest that CGRP might interact more with the catecholaminergic system than with the cholinergic system.…”