In all social insects, including ants, termites and social bees, their tremendous evolution and ecological dominance are due to their efficient social organizations and communication systems. Social insects communicate with each other by means of various sensory modalities, but chemical communication has been studied well in chemical ecological aspects. Chemical communication via pheromones affects or regulates ant’s behaviors or physiological situations; mutual attraction, repulsion, identification of species and kin, courtship and parental care, establishment of dominance and division of labor. Chemistry of pheromones has been considerably progressing not only in structural identification but also in their functional meaning for behavioral regulation.
  Here, we document 1) nestmate recognition, 2) pheromonal trailing or alarm behavior and 3) involvement of hormonal regulation.
1) For ants, cuticular hydrocarbons (CHC) blends produce by non-nestmate elicit overt aggression. Recently, a novel chemosensillum that functions in nestmate discrimination was found on the antennae of the Japanese carpenter ant. We focus on the role of this type of sensilla for a peripheral recognition mechanism in detecting colony specific chemical signals.
2) Trail pheromones and alarm pheromones were chemically identified in leaf cutting ants and Carpenter ant respectively. In primary olfactory centre (AL), it was reported a putative gromerulus sensitive to the trail pheromones. Its also was reported projection neurons for alarm information processing.
3) Finally we mention about octopamine, one of biogenic amines, controlling the social bond among individuals in the same colony.
  Previous reports from the fields of chemistry and chemical ecology have clarified which chemicals are effectively used for pheromonal communication in ants. In future, researchers should progress this line of studies in neurological point of view.

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Neuromodulation is often thought to have a static, gain-setting function in neural circuits. We found that biphasic-bidirectional neuromodulatory actions of serotonergic neurons in the mollusc, Tritonia diomedea, arise from the dynamics of two independent intracellular events, and further investigated the mechanism underlying such neuromodulatory actions that we termed spike timing-dependent neuromodulation (STDN). The Dorsal Swim Interneurons (DSIs) are serotonergic neurons intrinsic to the Tritonia swim central pattern generator (CPG). When stimulated at physiological rates, they alter the size of synaptic currents evoked by another CPG neuron, Ventral Swim Interneuron B (VSI), in a time-varying manner; there is an initial potentiation phase lasting 15 seconds, followed by a depression phase lasting up to 2 min. We have determined that STDN is caused by two independent responses of VSI to serotonin (5-HT) released from DSI. The depression phase is caused by a serotonergic enhancement of a 4-aminopyridine (4-AP)-sensitive, voltage-gated outward current ( I _A). The depression phase, but not the potentiation is blocked by 4-AP. Pharmacological experiments show that this synaptic potentiation is dependent upon intracellular stores of Ca ²⁺. Thus, the dynamic neuromodulatory change in synaptic strength is caused by independent mechanisms within VSI: an enhancement of vesicle release and an enhancement of I _A. The dynamics of neuromodulation may play a role in production of the motor pattern by the CPG.

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[in Japanese]

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