Observation On The Function Of 5-HT In The Brain And The Thoracic Ganglion Of Polyrhachis Vicina Roger

Ant Polyrhachis vicina Roger are social insects with clear division oflabor. The polymorphism and clear division of labor decide that they have developedneural system. Because of its concentrated nerve system, the ants are good experimentalmaterial to study the instructures and the fuctions of insects' nerve system. It is easy toobserve and operate on this species.The nerve system is the bases of sense, locomotion, study and memory in animals.Neurotransmitter is the activity base of the nerve cells. Transmitter molecules combinewith its receptors. Then the process has a interaction with the penetration of ions andproduces a postsynapt potential and makes the communication of information. In thisstudy, using Paraffin embedding tissue section technique and immunohistochemical SPmethod, we have investigated the distribution of 5-HT in the brains and in the thoracicganglions of different ant castes. We trained the work ant through behavioral method tostudy the ability of learning and memory of P. Vicina Roger, and compaired thedifference of 5-HT expression to find if the level of 5-HT changed.1. All brain regions of the three ant castes are innervated by extensive aborizations of5-HT fibers. The most intense immunoreactivity is found in the peduncle of themushroom bodies, the central complex, the optic lobes and the antennal lobes.Fainter immunoreactivity appears in the calyxes of the mushroom bodies. Itsdistribution has a close relationship with the ants' behavior features. In worker ants,the intense immunoreactivity appears in the peduncle of the mushroom bodies andthe central complex. And it is fainter in the central complex of the males and thefemales. The results show it may be caused by the relative little activity afterwedding flying. The 5-HT immunoreactive fibres in the optic lobes presentdelamination phenomena. It illuminates that 5-HT plays an important role in theprocesses of vision information and light information. Compared with the otherbrain areas, 5-HT immunoreactivities are fainter in the olfactory glomerulus of themidbrain. It shows that 5-HT is not the main neurotransmitter in the antennal lobesand has a little function in the process of olfaction information. Dorsal lobes have 5-HT immunoreactivity fibres. We presume it has a relationship with developedantenna and multiple locomotions. Probably, 5-HT has a function to maintain theexciting stimulation of sense nerve cells.2. After we trained the work ants by Y-maze, we find that the ability of learning andmemory is obvious in work ants. Compared with the 5-HT expression in work antsafter training, there are obvious difference in the mushroom bodies andunconspicuous difference in the central complex. The results imply that themushroom bodies play an important role in the process of learning and memory ofthe work ants. And it indicates that the 5-HT function is related with synapticplasticity. The effects of 5-HT on learning and memory refer to manyneurotransmitters, their receptors and signal pathway. Every steps is under acomplex modulation network.3. There are intense immunoreactivities of 5-HT in the thoracic ganglions and haveobvious differences. The immunoreactivity is the most intensen in the work ants.And it is fainter in the female ants than the male ants. We analyse this phenomenonby the behaviors in different castes. The worker ants' activities is very frequent. Themale ants are more active than the female ants because of wedding flying andlooking for the females. The female ants go out of nest a few. 5-HT is an importantneurotransmitter produced by tiredness in the central nerve system. The moreactivity, the more synthesize of 5-HT in the brain. The brain will be sensitive toother tire informations. Then the organisms have a poor activity.In this paper, for the first time, we studied the expression of 5-HT in the brains and inthe thoracic ganglions of different ant castes. And we trained the work ants throughbehavioral method to study the work ants' ability of learning and memory. Thedistribution of 5-HT in the ants had a close relationship with the behaviors of differentcastes. This conclusion clearly explained the connection of animals' behaviors and theirfunctions of organism. To adapting the complex environment, animal's nerve systemgathers kinds of stimulating information, translates into instructions to deliver to thesports system, and makes quick and right decisions. These changes can alter the innerenvironment of the organism and represents with the proper behaviors in the out side.