Distribution of alpha‐neoendorphin, ACTH (18–39) and beta‐endorphin (1–27) in the alpaca brainstem

Abstract

Using an immunocytochemical technique, we have studied in the alpaca brainstem the distribution of immunoreactive structures containing prodynorphin (alpha-neoendorphin)- and pro-opiomelanocortin (adrenocorticotrophin hormone (18-39) (ACTH), beta-endorphin (1-27))-derived peptides. No peptidergic-immunoreactive cell body was observed. Immunoreactive fibres were widely distributed, although in most of the brainstem nuclei the density of the peptidergic fibres was low or very low. In general, the distribution of the immunoreactive fibres containing the peptides studied was very similar. A close anatomical relationship occurred among the fibres containing alpha-neoendorphin, ACTH or beta-endorphin (1-27), suggesting a functional interaction among the three peptides in many of the brainstem nuclei. The number of fibres belonging to the prodynorphin system was higher than that of the pro-opiomelanocortin system. A moderate/low density of immunoreactive fibres was observed in 65.11% (for alpha-neoendorphin (1-27)), 18.18% (for ACTH) and 13.95% (for beta-endorphin) of the brainstem nuclei/tracts. In the alpaca brainstem, a high density of immunoreactive fibres was not observed. The neuroanatomical distribution of the immunoreactive fibres suggests that the peptides studied are involved in auditory, motor, gastric, feeding, vigilance, stress, respiratory and cardiovascular mechanisms, taste response, sleep-waking cycle and the control of pain transmission.

Neuroanatomical distribution of the enkephalinergic and tachykininergic systems in the alpaca brainstem: an immunohistochemical study

“…This work was as well approved by the Research Commission of the Cayetano Heredia Peruvian University (Lima, Peru). Because previous studies on the distribution of neuropeptides were carried out in males [17][18][19][20][21][22] and, in order to compare the results observed here with previous works performed in the alpaca brainstem [17][18][19][20][21][22], the present study was carried out in male alpacas. Five adult alpacas (Lama pacos) (70-80 kg; 5-8 years) were obtained from the Cayetano Heredia Peruvian University (Faculty of Veterinary Medicine and Animal Sciences).…”

“…As previously reported [5,[17][18][19][20][21][22], immunoreactive fibers were graded into four categories: single (a few immunoreactive fibers; Fig. 2b), low, moderate (Fig.…”

“…Five adult alpacas (Lama pacos) (70-80 kg; 5-8 years) were obtained from the Cayetano Heredia Peruvian University (Faculty of Veterinary Medicine and Animal Sciences). As previously reported [17][18][19][20][21][22], alpacas were maintained at 0 m altitude, under standard conditions of temperature and lightning and were provided with free access to food and water and, from birth to the moment of the perfusion; animals were kept at sea level. Tissue preparation.…”

“…This was performed by following frontal planes of the alpaca brainstem (the brain atlas used here is available from the Mammalian Brain Collections of the University of Wisconsin, Madison, U.S.A.). For mapping and nomenclature of the brainstem nuclei, we also followed previous published works performed in this camelid [17][18][19][20][21][22]. In addition, contiguous sections to those reacted for SP or MET were stained with cresyl violet to delineate the brainstem nuclei in which immunoreactive structures were observed.…”

“…Alpacas can live from the sea level to 5,000 m altitude, indicating that this species has special physiological adjustment mechanisms, as are those related to providing sufficient blood flow to the brain and the implication of these unique features in the neuroanatomical organization of some CNS nuclei. In addition to those works focused on the alpaca reproductive mechanisms, several studies have been previously performed on the neuroanatomical location of neuropeptides (calcitonin gene-related peptide, somatostatin-28 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), neurotensin, leucine-enkephalin, alphaneo-endorphin, adrenocorticotropic hormone (18-39), beta-endorphin ) in the alpaca brainstem [17][18][19][20][21][22]. In addition, a recent study has shown a close neuroanatomical relationship between the enkephalinergic (methionine-enkephalin) and tachykininergic (substance P) systems in the alpaca diencephalon and the presence of some neuropeptides (e.g., neurotensin) has also been reported in this region of the alpaca CNS [5,23].…”