Mapping of CGRP in the alpaca diencephalon
Highlights
► CGRP-immunoreactivity is reported in the alpaca diencephalon. ► Immunoreactive fibers were widely distributed throughout the thalamus and hypothalamus. ► Cell bodies were only observed in the hypothalamus. ► Cell bodies were found in the paraventricular/ventromedial and supraoptic nuclei. ► Perikarya were also found in the anterior, lateral, dorsal and posterior areas.
Introduction
In South America camelid research has been focused in general on their reproductive mechanisms (Bravo et al., 1996, Correa et al., 1997, Ratto et al., 1997, Ratto et al., 2005, Ratto et al., 2006) due to the economic importance of their wool, although recently the distribution of three neuropeptides belonging to different families of peptides (leucine-enkephalin, calcitonin gene-related peptide (CGRP), somatostatin-28 (1–12)) and tyrosine hydroxylase has been reported in the alpaca central nervous system (brainstem and diencephalon) (de Souza et al., 2007, de Souza et al., 2008, Coveñas et al., 2011, Marcos et al., 2011). In this sense, the distribution of CGRP has been reported in the alpaca brainstem (de Souza et al., 2008) and the colocalization of this neuropeptide with tyrosine hydroxylase has been also studied in the same central nervous system region of this ungulate (Marcos et al., 2011). Comparing the distribution of immunoreactive cell bodies containing the above-mentioned neuropeptides, it should be remarked that both the distribution and number of cell bodies containing CGRP are considerably higher than those observed for perikarya containing leucine-enkephalin or somatostatin-28 (1–12) (de Souza et al., 2007, de Souza et al., 2008, Coveñas et al., 2011). In all cases, these studies were carried out in control animals; that is, in alpacas not treated with colchicine. Thus, the aim of this study was to increase our knowledge of the chemical neuroanatomy of the CGRP system in the alpaca brain, and in this sense here we report the distribution of CGRP-immunoreactive fibers and cell bodies in the alpaca thalamus and hypothalamus according to an immunohistochemical technique. The distribution found is compared with that described for CGRP in the mammalian diencephalon (Skofitsch and Jacobowitz, 1985a, Skofitsch and Jacobowitz, 1985b; see Palkovits, 1988, Coveñas et al., 2001, Coveñas et al., 2002) and with the distribution of somatostatin-28 (1–12) recently described in the alpaca thalamus and hypothalamus (Coveñas et al., 2011).
The diencephalon is an important region of the central nervous system and is involved in food intake, olfactory, neuroendocrine, vestibular, somatosensorial, stress, thermoregulation, blood pressure, visual, auditive, taste, immunoregulatory, drinking, reproductive and nociceptive mechanisms (see Swaab, 1997, Coveñas et al., 2001, Coveñas et al., 2002 for a review). The neuropeptide CGRP, composed of 37 amino acids, has also been implicated in many physiological actions (e.g., hyperthermia, vasodilatation, locomotor activity, social behavior and regulation of astrocytes) (see de Souza et al., 2008) and hence knowledge of the distribution of neuropeptides (e.g., CGRP) in the alpaca brain will serve in the future to better understand, for example, the involvement of these substances in reproductive and social behavior, as well as at different altitudes, since this camelid lives from sea level to heights of more than 5000 m, suggesting the possible existence of special and unique regulatory mechanisms.
Section snippets
Animals
We used seven male adult alpacas (Lama pacos) (70–80 kg) obtained from the Cayetano Heredia Peruvian University (Faculty of Veterinary Medicine and Animal Sciences, Lima, Peru). As previously reported (Coveñas et al., 2011), the animals were maintained at 0 m (sea level) from birth to death under standard conditions of light (lights on at 06:00 h and off at 20:00 h) and temperature (26° C) and had free access to food and water. The experimental design, protocols, and procedures of this work were
Results
Fig. 1 and Table 1 show the distribution and density of immunoreactive fibers and cell bodies containing CGRP in the alpaca diencephalon. In the seven animals used in this study both the distribution and density of the immunoreactive structures observed in this zone were fairly similar. Thus, in 33 nuclei/regions (18 thalamic/epithalamic, 14 hypothalamic and the subthalamic nucleus) of the alpaca diencephalon we found CGRP-immunoreactive fibers (in general, thin, short/medium in length,
Discussion
This is the second report describing the distribution of fibers and cell bodies containing neuropeptides in the alpaca diencephalon, since a previous study showed the distribution of somatostatin-28 (1–12) (Coveñas et al., 2011). On comparing the distribution of somatostatin-28 (1–12)-immunoreactive fibers in the alpaca thalamus with that of the immunoreactive fibers containing CGRP, it seems that the distribution of somatostatin-28 (1–12)-immunoreactive fibers is slightly more widespread (
Acknowledgements
This work has been supported by the Ministerio de Educación y Ciencia (BFU2005-02241/BFI), Spain and the Ministerio de Ciencia e Innovación (BFU2008-03369/BFI), Spain and by the CONCYTEC: PROCYT project 2006, Peru. The authors thank Professor Gerard Tramu (University of Bordeaux I, France) for kindly providing the CGRP antiserum and N. Skinner for stylistic revision of the English text.
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