Differential effects of photoperiod and temperature on hypothalamic monoaminergic activity in the teleost Channa punctatus (Bloch) |
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Authors: | I A Khan K P Joy |
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Institution: | (1) Centre of Advanced Study in Zoology, Banaras Hindu University, Varanasi, 221 005, India;(2) Centre of Advanced Study in Zoology, Banaras Hindu University, Varanasi, 221 005, India |
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Abstract: | In Channa punctatus maintained under ambient photothermal conditions (10.5L:13.5D; 13 ± 2°C) in the postspawning season, hypothalamic dopamine
(DA) and norepinephrine (NE) content varied diurnally, but serotonin (5-HT) and monoamine oxidase (MAO) did not. Exposure
of the fish to high temperature (25 ± 2°C), with or without altering the photopheriod, increased the NE and DA content, and
NE turnover but decreased DA turnover. Increasing the photoperiod (16L:8D) alone had no significant effect on catecholaminergic
(CA) content or activity. When the fish were exposed to long photoperiod, with or without altering the temperature, a day-night
variation in 5-HT content and activity was induced in the postspawning season. An increase in temperature alone had no significant
effect on 5-HT content or activity. Hypothalamic MAO activity was elevated in fish exposed to high temperature alone, or in
combination with long photoperiod, but was not affected significantly by long photoperiod treatment. These results indicate
that CA activity is influenced largely by ambient high temperature, whereas serotonergic activity is controlled primarily
by photoperiod, with high temperature having an additive effect. MAO activity seems to be influenced by both temperature and
photoperiod in this species. |
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Keywords: | photoperiod temperature hypothalamus norepinephrine dopamine 5-hydroxytryptamine MAO |
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