Octopamine Regulates The Difference In Olfactory Learning Of Bactrocera Dorsalis Under Different Sugar Rewards

Learning and memory are two inseparable neural processes that can change insect preferences.Octopamine(OA)is commonly found in insects and regulates their learning and memory behaviors.This paper focuses on the important oriental fruit fly Bactrocera dorsalis,We explored the effect of octopamine on the olfactory learning and memory of male adult B.dorsalis.We used the classic conditional training method to determine the rewarding olfactory learning ability of male orange fruit fly male adults combined with sweet orange essential oil under different sugars.Then,the effects of octopamine antagonists on the olfactory learning and memory of B.dorsalis are investigated through behavioral and pharmacological methods.The main findings are as follows:(1)The effects of Different Types of Sugar on Learning and Memory Formation in B.dorsalis.Combining sweet orange essential oil with different types of sugar(feeding reaction after being nutritious and taste sensation,sucrose;Non-nutritive but taste-induced eating reaction,D-arabinose and L-glucose;nutritious odorless sugar,D-sorbitol,mannitol)B.dorsalis were given rewarding olfactory training five times.The beak-stretching response rates of orange B.dorsalis to different types of sugars were 81.36%,55%,50.85%,20.69%,and 38.33%,respectively.After 24 hours of rewarding olfactory training on B.dorsalis,the beak extension response rates of B.dorsalis were 79.66%,13.33%,16.67%,20%,and 36.67%.Learn to find that sweetness can be linked to smell to form short-term memory.However,the memory decline of the B.dorsalis is faster under the action of the non-nutritive sweet sugars D-arabinose and L-glucose.The results show that the B.dorsalis can learn and evaluate the quality of sugar through taste and nutritional value,and use the mechanism after feeding to remember the nutritional sugar for a long time.(2)The effects of the Same Type of Sugar on the Learning and Memory of B.dorsalis.Selecting three nutritious and taste sensation sugars: sucrose,fructose and glucose,combined with sweet orange essential oil for reward olfactory learning training for 5 times,the beak extension rate of B.dorsalis was 80%,61.67%,45%;In the memory test after 24 hours,the beak extension rate of B.dorsalis was 71.42%,36.67%,and 43.33%,respectively.In order to further confirm the influence of pre-ingestive and post-ingestive signals on learning and memory formation,cross-training is used,that is,one kind of sugar is used for forefoot stimulation,and another sugar is fed after protruding the beak.After the second training,in the 24 h memory test,it was only found that the training group taking fructose significantly reduced the beak extension rate.The results showed that B.dorsalis can maintain a high level of memory at 24 h under the reward of sucrose or glucose,but under the reward of fructose,the memory has a larger decline in 24 h,and the results of cross-stimulation indicate that B.dorsalis may pass through pre-ingestive(taste)and post-ingestive(nutrition)signals distinguish these three sugars.(3)The effect of octopamine on olfactory learning in B.dorsalis.Before the reward training,the octopamine antagonists Mianserin and Epinastine were injected into the B.dorsalis,and 500 μM antagonist was injected 20 minutes,30 minutes and 60 minutes in advance.The beak extension rate of the two octopamine antagonists in the 20 min group was significantly lower than that in the control group and the 30 min and 60 min groups,while there was no significant difference between the 30 min and 60 min groups and the control group.When the injection time was 20 min,there was no difference in blocking effect at the two concentrations.The results show that octopamine participates in the regulation of reward olfactory learning of B.dorsalis and has a time effect.By further verifying the effects of the two antagonists on punitive olfactory learning,it was found that octopamine does not participate in the regulation of pungent olfactory learning of B.dorsalis.(4)The effects of Octopamine on Olfactory Learning and Memory of B.dorsalis.Twenty-four hours after the end of the rewarding olfactory learning training,the octopamine antagonists Mianserin and Epinastine were injected into the B.dorsalis,and 50μM and 500 μM antagonists were injected 30 minutes and 60 minutes respectively.When the two octopamine antagonists were in the 30 min group,the antagonists at the two concentrations had better antagonistic effects;in the 60 min group,the effect was only better at 500 μM.The results show that octopamine is involved in regulating the retention of reward olfactory memory of B.dorsalis,and there is a time and concentration effect.By further verifying the effect of the two antagonists on punitive olfactory learning,it was found that octopamine does not participate in regulating the retention of pungent olfactory memory in B.dorsalis.