Pituitary cocaine- and amphetamine-regulated transcript expression depends on the strain, sex and oestrous cycle in the rat
J Neuroendocrinol. 2006-06-01; 18(6): 426-433
DOI: 10.1111/j.1365-2826.2006.01435.x
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1. J Neuroendocrinol. 2006 Jun;18(6):426-33.
Pituitary cocaine- and amphetamine-regulated transcript expression depends on the
strain, sex and oestrous cycle in the rat.
Kappeler L(1), Gautron L, Layé S, Dantzer R, Zizzari P, Epelbaum J, Bluet-Pajot
MT.
Author information:
(1)UMR 549 Inserm, Université-Paris-René-Descartes, Faculté de Médecine, Paris,
France.
Cocaine- and amphetamine-regulated transcript (CART) mRNA and peptides are
abundant in the adenohypophysis, but their role in pituitary function has not yet
been elucidated. CART peptides were recently shown to colocalise with luteinising
hormone (LH) or prolactin in rat anterior pituitary, and contradictory results
concerning the peptide effects on pituitary hormonal secretions were obtained in
vitro from pituitary cell cultures. Thus, we reinvestigated the expression of
CART mRNA within the pituitary. Immunohistochemistry for pituitary hormones was
performed on sections from adult male Wistar rats followed by in situ
hybridisation using CART mRNA antisense 35S-labelled probes. The most represented
CART-expressing cells were lactotrophs (42 +/- 1% of CART cells) and gonadotrophs
(32 +/- 3%), followed by thyrotrophs (10 +/- 2%), corticotrophs (7 +/- 2%) and
somatotrophs (6 +/- 1%). In the pars tuberalis, CART mRNA was easily detectable
in gonadotrophs and lactotrophs and, to a lesser extent, in corticotrophs and
thyrotrophs. CART peptide was quickly and potently released from perifused
pituitary by depolarisation (K+ 30 mM for 15 min; 465 +/- 37% over basal release,
n = 5). Gonadotrophin-releasing hormone and thyrotrophin-releasing hormone (0.1
microM) were also active to a lesser extent (138 +/- 11% and 71 +/- 17, n = 7,
respectively). CART (0.1 microM) did not modify basal LH or prolactin release but
selectively inhibited K+-induced LH release without affecting K+-induced
prolactin secretion. Pituitary CART mRNA and content were sex dependent and
varied during the oestrous cycle, being lower in dioestrous 2. Pituitary CART
content also varied widely amongst rat strains being five to six-fold higher in
Wistar and Fischer rats compared to Brown Norway and Lou C rats. Ageing
differentially affected pituitary CART mRNA and content, resulting in a marked
decrease in Lou C and an increase in Wistar and Sprague-Dawley rats. Taken
together, these results suggest that pituitary CART expression is dependent of
the sex steroid environment and may be physiologically involved in LH secretion.
DOI: 10.1111/j.1365-2826.2006.01435.x
PMID: 16684132 [Indexed for MEDLINE]