Download effect of heat and cold exposure on rat brain monoamine oxidase

Abst. # 46
EFFECT OF HEAT AND COLD EXPOSURE ON THE RAT BRAIN
MONOAMINE OXIDASE AND ANTIOXIDATIVE
ENZYME ACTIVITIES
J. Djordjevic, G. Cvijic, V. Davidovic
Institute of Physiology and Biochemistry, Faculty of Biology, University of Belgrade,
Studentski trg 16, 11000 Belgrade, Serbia and Montenegro, email: [email protected]
The maintenance of homeostasis requires precise coordination of autonomic, neuroendocrine
and behavioral response to the stressor perceived. Although the entire central nervous system
is involved in the maintenance of homeostasis participating in the organization of stress
response, some areas may have specific roles in these regulatory mechanisms. Higher centers
such as the neuroendocrine hypothalamus, the limbic system and cerebral cortex are the
modulatory centers of the stress response and they exert their effects through actions on the
brain stem and spinal neurons. Brain catecholaminergic neurons are involved in the central
processing of stress response. Neurons in the ventrolateral and dorsomedial medulla
oblongata are the major sources of noradrenergic nerve terminals in the hypothalamus and the
limbic system. Their activation is stressor specific, certain stressors activate them rapidly
while others may have only minor influences. Thus, аs a result of very intense catecholamine
metabolism, free radicals may be generated and consequently antioxidative enzymes activated
in the brain region, the hypothalamus and hippocampus.
Bearing in mind the facts mentioned above, we examined changes in MAO activity, the main
enzyme involved in catecholamine metabolism, as well as the activities of antioxidant
enzymes copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase
(MnSOD) and catalase (CAT) under the influence of physical stressors, cold and heat. The
male rats of Wistar strain were exposed to the extreme environmental temperature 6°C for
180min and 38°C for 60min, in a temperature controlled chambers. Animals were killed
immediately after stress exposure, heads were removed, hypothalamus and hippocampus
excised, dissected and used for the measurements of enzyme activities.
The exposure of animals to cold stress for 180 min did not change hypothalamic MAO and
CAT activity as compared to controls maintained at room temperature, whereas the
CuZnSOD (p<0.05) and MnSOD activity (p<0.01) was increased. After a 60 min heat
exposure MAO activity decreased (p<0.01), MnSOD and CAT activity remained unchanged
whereas CuZnSOD activity significantly increased in this brain region (p<0.001) in respect to
control values. Under the same experimental conditions the changes in the hippocampal
MAO, CuZnSOD and MnSOD activity were similar to those obtained in the hypothalamus.
Also, cold stress did not affect the hippocampal CAT activity whereas the heat stress resulted
in the decrement of CAT activity (p<0.01) in this brain region.
In conclusion, extreme environmental temperatures caused stressor specific changes in the
hypothalamic and hippocampal MAO and antioxidative enzyme activities, being dependent
on the stressor applied (cold or heat) but not on the brain region studied (the hypothalamus or
hippocampus).