2005 Fiscal Year Final Research Report Summary
Neural mechanism of reproductive timer
| Project/Area Number |
16570062
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Animal physiology/Animal behavior
|
|---|
| Research Institution | OKAYAMA UNIVERSITY |
|---|
Principal Investigator |
SAKAI Masaki Okayama Univ., Grad.Sch.Nat.Sci.Tech., Professor, 大学院・自然科学研究科, 教授 (30027502)
|
|---|
| Project Period (FY) |
2004 – 2005
|
| Keywords | male cricket / reproductive behavior / time / timer / reproductive cycle / spermatophore / terminal abdominal ganglion / neuron |
|---|
| Research Abstract |
To search the reproductive timer (1 h) in the terminal abdominal ganglion in the male cricket, I recorded extracellular spike activity of efferent motor activity influencing the genital organs which are involved in spermatophore formation. As the timer starts at spermatophore preparation (SP) which occurs several minutes after copulation, I analyzed spike frequency for more more than one hour after SP. The following results were obtained. 1)Guiding rod : one of the neurons which was active after SP stopped its activity 8 min after SP. 2)Epiphallus : one neuron gradually decreased its spike activity after SP and finally stopped in 8 min, while the other neuron gradually increased after SP and reached at a constant level in 10 min. 3)Ventral lobes : one neuron which discharged at high frequency immediately after SP gradually increased its activity in 30 min and reached a stable level in 40 min, while the other neuron began to discharges 30 min after SP and reached the stable level in 40
… More
min. 4)Median pouch : two kind of burst discharge was present. One of them which had tonic activity immediately after SP become rhythmic bursting in 30 min and reached a constant level in 40 min. These activation patterns of motoneurons did not change when the connectives were cut between the terminal abdominal ganglion and the 6thabdominal ganglion indicating that they are intrinsic and possibly under the control of the reproductive timer for the time-fixed sexually refractory stage. On the other hand, ablation of each organ and transection of their nerves caused the abnormality in the spermatophore. That is, the time-fixed activity of the neurons innervating the genital organs is indispensable to form the normal shape of the spermatophore although spermatophore material can make gross structure by itself. To examine if the timer is influenced by internal and external factors, the males were restrained under the different stressful conditions for 30 min after SP ; some were paired with a male and others were fixed on the substrate. Then, when paired with a female, the time for sexual refractory stage was shorted by 20-30%. These may be due to octopamine because it is known to accelerate the timer and stress induces octopamine secretion in crickets. These results suggest that the reproductive timer is closely tied to the spermatophore production system and influenced by animal's internal condition to some extent.. Less
|
