General and Comparative Endocrinology 149 (2006) 190–196
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doi:10.1016/j.ygcen.2006.05.012
Involvement of neuropeptide Y Y1 receptors in the regulation
of LH and GH cells in the pituitary of the catWsh, Clarias batrachus:
An immunocytochemical study
Minakshi Mazumdar
a
, Bechan Lal
b
, Amul J. Sakharkar
a
, Makrand Deshmukh
c
,
Praful S. Singru
d
, Nishikant Subhedar
a,¤
a
Department of Pharmaceutical Sciences, R.T.M. Nagpur University Campus, Nagpur 440 033, India
b
Department of Zoology, Banaras Hindu University, Varanasi, India
c
N.H. College of Science, Bramhapuri, District Chandrapur, India
d
Division of Endocrinology, Diabetes, Metabolism and Molecular Medicine, Tufts-New England Medical Center, Boston, MA 02111, USA
Received 21 March 2006; revised 5 May 2006; accepted 24 May 2006
Available online 7 July 2006
Abstract
Although neuropeptide Y (NPY) has been known to inXuence the release of luteinizing hormone (LH) and growth hormone (GH)
from the pituitary gland of teleosts, the NPY receptor subtypes involved in the regulatory processes have not been fully deWned. An
attempt has been made to study the involvement of NPY Y1 receptors, if any, in mediating the NPY-triggered stimulation of the LH and
GH secreting cells in the pituitary of the catWsh, Clarias batrachus. NPY (10 ng/g of body wt) or NPY Y1 receptor agonist (Leu
31
-Pro
34
-NPY,
3 ng/g of body wt) were administered by the intracranial route and the responses by the LH and GH cells in the pituitary were investi-
gated with the help of immunocytochemistry. Both the agents caused a highly signiWcant decrease (P < 0.001) in the immunoreactivity of
LH cells. However, the treatment with NPY Y1 receptor antagonist (BIBP 3226, 1 ng/g of body wt), prior to NPY or NPY Y1 agonist,
blocked the response by the LH cells; the proWle of the cells was quite similar to that of the saline-injected control Wsh. GH cells also
showed similar pattern of responses to these treatments. While NPY and NPY Y1 receptor agonist caused signiWcant (P < 0.001) decrease
in the GH immunoreactivity, pretreatment with the NPY Y1 antagonist blocked the response. These results suggest that NPY may exer-
cise a secretogogue-like action on the LH and GH cells in the pituitary of C. batrachus via NPY Y1 receptors.
© 2006 Elsevier Inc. All rights reserved.
Keywords: Fish reproduction; Neuroendocrine regulation; NPY receptors; Pituitary; Peptide; Teleosts
1. Introduction
The role of neuropeptide Y (NPY) in the regulation of
luteinizing hormone (LH) release is clearly established in
mammals (Kalra et al., 1997). NPY is known to interact
with a family of seven transmembrane G-protein coupled
receptors. Five NPY receptor subtypes have been cloned
from mammals (Y1, Y2, Y4, Y5, and Y6) and several addi-
tional receptors such as Y3 have been postulated, based on
pharmacological proWles using various tissue preparations
(for review see Berglund et al., 2003). Some attempts have
been made to characterize the nature of NPY receptor sub-
types involved in the regulation of LH and growth hor-
mone (GH) secretion. While Y2 receptors have been
suggested to be involved in the regulation of LH and GH
secretion in male rats (Aguirre et al., 1991), Kalra et al.
(1992) reported that NPY Y1 receptors, but not the Y2
receptors, are involved in the regulation of GnRH and LH
secretion in female rats. Rudolf et al. (1997) demonstrated
that NPY acts through Y1 receptor subtype to augment
LH release. Some useful information is also available on
teleosts. In goldWsh, NPY has been shown to regulate the
*
Corresponding author. Fax: +91 712 2549521.
E-mail address: nksubhedar@hotmail.com (N. Subhedar).