J Infertil Reprod Biol, 2020, Volume 8, Issue 3, Pages: 57-60. https://doi.org/10.47277/JIRB/8(3)/57  
The Effects of Dopamine and Glutamate Agonists  
on Brain Histology and Food Intake of Quails  
Exposed to Environmental Heat Stress  
Shaghayegh Hajian Shahri  
Department of Basic Veterinary Science, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran  
Received: 10/06/2020  
Accepted: 29/08/2020  
Published: 20/09/2020  
Abstract  
The present study was aimed to investigate the effects of apomorphine (dopamine agonist) and glutamate on quails  
exposed to environmental heat stress. Thirty two male Japanese quails were randomly divided into four groups. Control  
quails maintained at 25-27 °C temperature while heat stressed quails exposed to outdoor temperature ranging from 25 to  
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1.7 °C for four days. Heat stressed quails were received saline, apomorphine (2 mg/kg, intraperitoneal ly) or glutamate  
(
2mg/kg, intraperitoneal ly). After two days food intake were recorded and then birds were euthanized to perform  
histopathological investigations. The cumulative food intake was significantly reduced in heat stressed quails, especially  
in the glutamate treated quails. The brain histopathological changes were even more severe in the heat treated  
group.Treatment with apomorphine could reduce the adverse effects of heat stress on brain. These results showed the  
protective effects of apomorphine on heat stress-induced anorexia in quails.  
Keywords: Quail, Heat stress disorders, Apomorphine, Glutamic acid  
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anorexic effect of beta receptors was reported to be mediated  
Introduction  
by serotonin but not histamine (12). The metabotropic and the  
inotropic glutamate receptor, was discovered in 1998. This  
neurotransmitter because of its unique effects, have diverse  
physiological roles in vertebrate including birds. It is also well  
known fact that glutamate have an important role in controlling  
physiological responses to different environmental stresses  
Heat stress is the main factor that could affect poultry  
industry all over the world, especially in the tropical region (1).  
The regulation of food intake is firmly related to the  
environmental factors and glutamate receptors (2). Heat stress  
is the main parameters that could affect food intake and weight  
gain in poultry industry (3). Previous studies have shown that  
heat stress could induce histological changes in different tissues  
including liver, heart and kidney (4). These impacts are mainly  
regulated through the interaction of several neuropeptides and  
neurotransmitters. Accumulating evidences have indicated that  
amino acids like glutamate and catecholamines such as  
epinephrine, norepinephrine and apomorphine, affect and  
control feeding behavior in birds and mammals exposed to heat  
stress (5, 6). Apomorphine - a non- selective dopamine agonist-  
have numerous physiological roles including food intake  
regulation birds (7). As shown in previous experiments, the  
administration of apomorphine increase appetite in rats and  
humans (8). It has been demonstrated that effect of  
neurotransmitters on water intake is evolutionarily conserved in  
quails, whereas its effect on food intake is in contrast to  
mammalian vertebrates (9). Intra-cerbroventricular (ICV)  
administration of dopamine in birds inhibits food intake.  
However, the effect of peripheral administration of dopamine  
agonists on food intake is not consistent with birds. Intravenous  
including  
thermal  
changes  
and  
photoperiods  
(
13). Intraperitoneal administration or systemic administration  
of glutamate and catecholamines could increase or decrease  
food intake in birds and mammals depending on environmental  
and physiological conditions (14-16).  
Considering previous studies about the effects of  
apomorphine and glutamate on feeding Behavior, it can be  
hypothesized that both systems possibly affect appetite in  
response to changes in physiological and thermal conditions.  
To the best of our knowledge, there is no scientific reports  
regarding the effects of apomorphine and glutamate on food  
intake of quails under heat stress. Furthermore recent work have  
suggested that acute or chronic heat stress could affect brain  
function or brain histology. Thus, the present study was carried  
out to examine the effects of apomorphine and glutamate  
administrations on food intake and brain histopathological  
changes of the brain in quails exposed to environmental heat  
stress.  
(
IV) administration of dopamine decreases food intake in  
quails, whereas in adult Japanese quail, it increases food intake  
and weight gain (10). It has been reported that the effect of  
apomorphine on birds is in contrast to what has previously  
described in the experiments. It has also been reported that  
glutamate mediates the inhibitory effect of apomorphine in  
quails (11). The mechanism underlying the apomorphine -  
induced hypoplasia in birds is still unclear, although the  
Materials and methods  
Thirty two adult male Japanese quails, weighing 90±5 gr  
were randomly divided into four groups. Group 1: control  
quails exposed to 25-27 °C temperature; Group 2: heat stressed  
quails exposed to outdoor temperature ranging from 25 to 41.7  
°C for four days; Group 3: heat stressed quails received  
apomorphine (2 mg/kg, intraperitoneally) for four days; and  
*
Corresponding author: Shaghayegh Hajian Shahri, Department of Basic veterinary Science, Faculty of Veterinary Medicine,  
University of Zabol, Zabol, Iran. Email: hajinezhad@uoz.ac.ir  
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