Elsevier

Brain Research

Volume 1362, 29 November 2010, Pages 40-47
Brain Research

Research Report
Cocaine- and amphetamine-regulated transcript (CART) peptide- immunopositive neuronal elements in the lateral septum: Rostrocaudal distribution in the male rat

https://doi.org/10.1016/j.brainres.2010.09.079Get rights and content

Abstract

The morphological features and distribution of cocaine- and amphetamine-regulated transcript peptide immunoreactivity (CART-IR) were studied in the lateral septum (LS) of male rats using light and electron microscopic immunocytochemistry and computer-aided densitometry. CART-IR was detected along the rostrocaudal axis of the LS in varicose axonal fibers only, although immunoreactive cell bodies and dendrites were not detected. Pericellular basket-like arrangements around immunonegative cell bodies were present. From among the targets of such pericellular baskets, glutamic acid decarboxylase (GAD)-immunopositive and NPY-immunoreactive somata were identified. Thin varicose axons were present in each section, whereas thick varicose axons were restricted to the sections of rostral position only. CART-IR was observed in varicose fibers forming a dense subependymal plexus, from which solitary varicose fibers entered the ependymal layer. The fine structure of varicosities was similar to that of other neuropeptide-containing fibers. Small varicosities established asymmetrical synaptic contacts mainly with dendrites and dendritic spines, and larger varicosities established symmetrical synapses with somata and dendritic shafts. CART-to-CART connections were not revealed. The density curve of the CART-IR along the rostrocaudal axis of LS was found to be paraboloid. CART is known as one of the most anorexigenic peptides. These results serve as basis for further physiological studies concerning the biological significance of lateral septal CART peptide in the regulation of food intake.

Research highlights

►CART-IR is present along the rostrocaudal axis of the rat LS in varicose nerve fibers. ►Two morphologically distinct types of fibers exhibited CART-IR. ►CART-IR around GAD- and NPY-containing cell bodies was revealed. ►Smaller boutons gave asymmetrical, while larger boutons formed symmetrical synapses. ►Densitometry of serial sections revealed a paraboloid distribution of CART.

Introduction

CART (cocaine- and amphetamine-regulated transcript) peptides were shown to be involved in a range of physiological processes such as feeding, locomotion, drug reward, reinforcement, and stress (Hunter and Kuhar, 2003). CART was first identified as an upregulated transcript in the rat nucleus accumbens following the acute administration of psychostimulants, cocaine and amphetamine (Douglass et al., 1995). This mRNA encodes a precursor peptide of either 116 or 129 amino acids. After the cleavage of some amino acids either the long form (102 amino acids) or the short form (89 amino acids) represents the active transmitter molecules. It was suggested that CART might be involved in feeding, since CART immunoreactivity was localized in brain regions associated with the regulation of food intake viz. the lateral hypothalamus (LH), ventromedial nucleus (VMN), dorsomedial nucleus (DMN), arcuate nucleus (Arc), paraventricular nucleus (PVN) of the hypothalamus, and nucleus accumbens (Koylu et al., 1997, Koylu et al., 1998). CART is expressed in several other brain regions, including the pituitary gland, nuclei of amygdala, olfactory bulb, Edinger–Westphal nucleus, and nuclei of the solitary tract (Koylu et al., 1998, Hurd and Fagergren, 2000, Kozicz, 2003). CART was also found at several peripheral locations that are involved in feeding, including the adrenal medulla, stomach, duodenum, the myenteric plexus of the gastrointestinal tract, and vagus nerve (Koylu et al., 1997, Koylu et al., 1998, Couceyro et al., 1998, Broberger et al., 1999, Kuhar and Yoho, 1999, Ekblad et al., 2003).

In the central nervous system, CART peptides are colocalized with other neurotransmitters and peptides that are also involved in the regulation of feeding, such as melanin-concentrating hormone in the DMN and LH (Broberger, 1999) and pro-opiomelanocortin (α-melanocyte-stimulating hormone) in the Arc (Elias et al., 1998). There is a functional interaction between CART peptide and the strongly orexigenic neuropeptide Y (NPY), since NPY-positive varicosities were observed around CART peptide-positive cell bodies in the PVN (Lambert et al., 1998). Kristensen et al. (1998) demonstrated that CART is a potent anorexigenic peptide. More specifically, a) intracerebroventricular administration of CART peptide fragments inhibits both normal and starvation-induced feeding in rats and completely blocks the feeding response induced by neuropeptide Y (Kristensen et al., 1998) and b) leptin receptors are present in CART-IR neurons in the Arc and leptin has been shown to be one of the strongest regulators of CART mRNA levels in the hypothalamus (Elias et al., 1998, Kristensen et al., 1998).

Previous studies indicated that the lateral septal area is rich in neuropeptides involved in the regulation of feeding such as galanin (gal), NPY, and opioids (Kovács et al., 2005); moreover, they respond with density changes to food deprivation (Kovács et al., 2007). The aims of the present study were to determine the presence of CART peptide in the LS, to describe the light and electron microscopic morphology of neuronal elements expressing the CART peptide, to reveal their fine structural characteristics and synaptic targets, and to determine the rostrocaudal distribution of CART in the lateral septum of male rats.

Section snippets

Results

CART-immunoreactive axonal fibers were detected along the rostrocaudal axis of the LS (Fig. 1). The immunoprecipitate was present in varicose nerve fibers; however, CART-IR was observed neither in local somata nor in dendrites. The dense immunoreactive plexus was not restricted to the lateral part of the septal complex; it also extended to the medial septum–diagonal band of Broca (MS/DB).

Discussion

This work provides immunocytochemical evidence on the presence of the CART peptide in the LS of male rats, and the major findings of this study are as follows: a) two types of CART-IR axon terminals were demonstrated with distinct distributional pattern, b) the distribution of CART-IR nerve plexuses showed a parabolic curve, and c) most of the synapses formed by CART-IR neuronal structures were asymmetric.

Animals and experimental groups

The experiments were carried out on 14 young adult male Wistar rats of the same age weighing 230–250 g. All animal procedures were conducted in accordance with the guidelines set forth by the European Communities Council Directive of 24 November 1986 (86/609/EEC) and the Animal Health and Welfare Institute of the Szent István University, and all efforts were made to minimize the number of animals and to keep animal stress, suffering, and discomfort to a minimum level. The Local Animal Welfare

Acknowledgments

The authors acknowledge the support of Hungarian Research FundOTKA T 43170 and are grateful for Dr. J.T. Clausen for the donation of the monoclonal CART antibody.

References (30)

  • J. Douglass et al.

    PCR differential display identifies a rat brain mRNA that is transcriptionally regulated by cocaine and amphetamine

    J. Neurosci.

    (1995)
  • E. Ekblad et al.

    Cocaine- and amphetamine-regulated transcript: distribution and function in rat gastrointestinal tract

    Neurogastroenterol. Motil.

    (2003)
  • C.F. Elias et al.

    Characterization of CART neurons in the rat and human hypothalamus

    J. Comp. Neurol.

    (2001)
  • C. Fekete et al.

    Origin of cocaine- and amphetamine-regulated transcript (CART)-immunoreactive innervation of the hypothalamic paraventricular nucleus

    J. Comp. Neurol.

    (2004)
  • C. Gall et al.

    Distribution of enkephalin, substance P, tyrosine hydroxylase and 5-hydroxytryptamine-immunoreactivity in the septal region in the rat

    J. Comp. Neurol.

    (1984)
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