1998 Fiscal Year Final Research Report Summary
Studies on burst activity of oxytocin neuron similar to that observed at the milk-ejection reflex in the brain slice
| Project/Area Number |
09670068
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental physiology (including Physical medicine and Nutritional physiology)
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| Research Institution | Fukui Medical School |
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Principal Investigator |
NEGORO Hideo Fukui Medical School, Vice-President, 副学長 (90018903)
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| Co-Investigator(Kenkyū-buntansha) |
HONDA Kazumasa Fukui Medical University, Physiology, Associate Professor, 医学部, 助教授 (50143946)
HIGUCHI Takashi Fukui Medical University, Physiology, Professor, 医学部, 教授 (70106326)
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| Project Period (FY) |
1997 – 1998
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| Keywords | milk-ejection reflex / oxytocin neuron / burst firing / noradrenalin / phenylephrine / brain slice / supraoptic nucleus / synchronized firing |
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| Research Abstract |
At the milk-ejection reflex in rats oxytocin neurons show burst firing for 2-3 seconds in response to sucking stimuli by pups. Consequently oxytocin is secreted from the posterior pituitary gland to eject milk from mammary gland. We aimed to know whether this burst activity originates from endogenous property of the oxytocin neurons. In addition, the involvement of nitric oxide (NO) in the burst fring was examined.
From 32 male rats hypothalamic slice preparations were made. We recorded from 65 neurons in the supraoptic nucleus using glass microelectrodes. We identified these neurons as oxytocinergic from their firing pattern. We observed burst activity in 4.6% of these neurons. The mean amplitude of the burst activity was 32.3 spikes, duration was 2.7 sec and after inhibition lasted for 2.7 sec. Additional forty one oxytocin neurons were recorded from other 26 rats after application of phenylephrine at the dose of 10^<-8> - 10^<-5> M.We observed burst activity in 39% of the neurons. The burst firing was irregular. We succeeded in recording from four paired oxytocin neurons, burst activity did not occur synchronously. NO donor, sodium nitroprusside, injected in the lateral ventricle of lactating rats inhibited milk ejection and Fos expression in the paraventricular and supraoptic nuclei.
From the these results, we conclude that the mechanism for the burst activity at the milk- ejection reflex at least in part originates from endogenous property of oxytocin neurons and that this mechanism is facilitated by adrenergic input. The synchronizing mechanism is located outside of the paraventricular or supraoptic nuclei and influenced by NO activity .
We will continue this project by introducing an equipment that can record from 64 neurons simultaneously.
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