研究等業績 - 原著論文 - 山方 恒宏
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Alarm pheromone processing in the ant brain: an evolutionary perspective.
Mizunami, Makoto Yamagata, Nobuhiro Nishino, Hiroshi
Front Behav Neurosci ( Frontiers in Behavioral Neuroscience ) 4 ( JUN ) 28 - 28 2010年 [査読有り]
研究論文（学術雑誌）
Social insects exhibit sophisticated communication by means of pheromones, one example of which is the use of alarm pheromones to alert nestmates for colony defense. We review recent advances in the understanding of the processing of alarm pheromone information in the ant brain. We found that information about formic acid and n-undecane, alarm pheromone components, is processed in a set of specific glomeruli in the antennal lobe of the ant Camponotus obscuripes. Alarm pheromone information is then transmitted, via projection neurons (PNs), to the lateral horn and the calyces of the mushroom body of the protocerebrum. In the lateral horn, we found a specific area where terminal boutons of alarm pheromone-sensitive PNs are more densely distributed than in the rest of the lateral horn. Some neurons in the protocerebrum responded specifically to formic acid or n-undecane and they may participate in the control of behavioral responses to each pheromone component. Other neurons, especially those originating from the mushroom body lobe, responded also to non-pheromonal odors and may play roles in integration of pheromonal and non-pheromonal signals. We found that a class of neurons receive inputs in the lateral horn and the mushroom body lobe and terminate in a variety of premotor areas. These neurons may participate in the control of aggressive behavior, which is sensitized by alarm pheromones and is triggered by non-pheromonal sensory stimuli associated with a potential enemy. We propose that the alarm pheromone processing system has evolved by differentiation of a part of general odor processing system.
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Differential odor processing in two olfactory pathways in the honeybee.
Yamagata, Nobuhiro Schmuker, Michael Szyszka, Paul Mizunami, Makoto Menzel, Randolf
Front Syst Neurosci ( Frontiers in Systems Neuroscience ) 3 ( DEC ) 16 - 16 2009年 [査読有り]
研究論文（学術雑誌）
An important component in understanding central olfactory processing and coding in the insect brain relates to the characterization of the functional divisions between morphologically distinct types of projection neurons (PN). Using calcium imaging, we investigated how the identity, concentration and mixtures of odors are represented in axon terminals (boutons) of two types of PNs - lPN and mPN. In lPN boutons we found less concentration dependence, narrow tuning profiles at a high concentration, which may be optimized for fine, concentration-invariant odor discrimination. In mPN boutons, however, we found clear rising concentration dependence, broader tuning profiles at a high concentration, which may be optimized for concentration coding. In addition, we found more mixture suppression in lPNs than in mPNs, indicating lPNs better adaptation for synthetic mixture processing. These results suggest a functional division of odor processing in both PN types.
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Neural pathways for the processing of alarm pheromone in the ant brain.
Yamagata, Nobuhiro Nishino, Hiroshi Mizunami, Makoto
J Comp Neurol ( Journal of Comparative Neurology ) 505 ( 4 ) 424 - 42 2007年12月 [査読有り]
研究論文（学術雑誌）
Social insects like ants exhibit sophisticated communication by means of pheromones, one example of which is the use of alarm pheromones to alert nestmates for colony defense. In the ant Camponotus obscuripes, we have reported that information about formic acid and n-undecane, alarm pheromone components, is processed in a set of specific glomeruli in the antennal lobe (primary olfactory center). Alarm pheromone signals are then transmitted, mainly via uniglomerular projection neurons (uni-PNs), to the protocerebrum (PR), where sensory signals are integrated to form motor commands for behavioral responses. In this study, we physiologically and morphologically characterized 63 alarm pheromone-sensitive PR neurons in ants by using intracellular recording and staining techniques. Most of the pheromone-sensitive PR neurons had dendrites in the mushroom body (MB), the lateral horn, or the medial PR. Some neurons with dendrites in these areas responded specifically to formic acid or n-undecane and may participate in the control of specific behavioral responses to each pheromone component. Other neurons responded also to non-pheromonal odors, in contrast to uni-PNs, most of which responded specifically to alarm pheromones. Responses to non-pheromonal odors were most prominent in efferent neurons of the MB lobe, suggesting that they may participate in integration of pheromonal and non-pheromonal information. We found a class of PR neurons that receives input in all of these pheromone-processing areas and terminates in a variety of premotor areas. These neurons may participate in the control of pheromone-sensitized aggressive behavior, which is triggered by non-pheromonal sensory stimuli associated with a potential enemy.
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Pheromone-sensitive glomeruli in the primary olfactory centre of ants.
Yamagata, Nobuhiro Nishino, Hiroshi Mizunami, Makoto
Proc Biol Sci ( Proceedings of the Royal Society B: Biological Sciences ) 273 ( 1598 ) 2219 - 25 2006年09月 [査読有り]
研究論文（学術雑誌）
Tremendous evolutional success and the ecological dominance of social insects, including ants, termites and social bees, are due to their efficient social organizations and their underlying communication systems. Functional division into reproductive and sterile castes, cooperation in defending the nest, rearing the young and gathering food are all regulated by communication by means of various kinds of pheromones. No brain structures specifically involved in the processing of non-sexual pheromone have been physiologically identified in any social insects. By use of intracellular recording and staining techniques, we studied responses of projection neurons of the antennal lobe (primary olfactory centre) of ants to alarm pheromone, which plays predominant roles in colony defence. Among 23 alarm pheromone-sensitive projection neurons recorded and stained in this study, eight were uniglomerular projection neurons with dendrites in one glomerulus, a structural unit of the antennal lobe, and the remaining 15 were multiglomerular projection neurons with dendrites in multiple glomeruli. Notably, all alarm pheromone-sensitive uniglomerular projection neurons had dendrites in one of five 'alarm pheromone-sensitive (AS)' glomeruli that form a cluster in the dorsalmost part of the antennal lobe. All alarm pheromone-sensitive multiglomerular projection neurons had dendrites in some of the AS glomeruli as well as in glomeruli in the anterodorsal area of the antennal lobe. The results suggest that components of alarm pheromone are processed in a specific cluster of glomeruli in the antennal lobe of ants.
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Fujiwara-Tsujii, Nao Yamagata, Nobuhiro Takeda, Takeshi Mizunami, Makoto Yamaoka, Ryohei
Zoolog Sci ( Zoological Science ) 23 ( 4 ) 353 - 8 2006年04月 [査読有り]
研究論文（学術雑誌）
The alarm pheromone of the ant Camponotus obscuripes (Formicinae) was identified and quantified by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Comparisons between alarm pheromone components and extracts from the major exocrine gland of this ant species revealed that the sources of its alarm pheromone are Dufour's gland and the poison gland. Most components of Dufour's gland were saturated hydrocarbons. n-Undecane comprised more than 90% of all components and in a single Dufour's gland amounted to 19 microg. n-Decane and n-pentadecane were also included in the Dufour's gland secretion. Only formic acid was detected in the poison gland, in amounts ranging from 0.049 to 0.91 microl. This ant species releases a mixture of these substances, each of which has a different volatility and function. When the ants sensed formic acid, they eluded the source of the odor; however, they aggressively approached odors of n-undecane and n-decane, which are highly volatile. In contrast, n-pentadecane, which has the lowest volatility among the identified compounds, was shown to calm the ants. The volatilities of the alarm pheromone components were closely related to their roles in alarm communication. Highly volatile components vaporized rapidly and spread widely, and induced drastic reactions among the ants. As these components became diluted, the less volatile components calmed the excited ants. How the worker ants utilize this alarm communication system for efficient deployment of their nestmates in colony defense is also discussed herein.
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Yamagata, Nobuhiro Fujiwara-Tsujii, Nao Yamaoka, Ryohei Mizunami, Makoto
Naturwissenschaften ( Naturwissenschaften ) 92 ( 11 ) 532 - 6 2005年11月 [査読有り]
研究論文（学術雑誌）
Communication by means of pheromones plays predominant roles in colony integration by social insects. However, almost nothing is known about pheromone processing in the brains of social insects. In this study, we successfully applied intracellular recording and staining techniques to anatomically and physiologically characterize brain neurons of the ant Camponotus obscuripes. We identified 42 protocerebral neurons that responded to undecane and/or formic acid, components of alarm pheromones that evoke attraction or evasive behavior, respectively. Notably, 30 (71%) of these neurons were efferent (output) or feedback neurons of the mushroom body, and many of these exhibited different responses to formic acid and undecane. Eight of the remaining 12 neurons had arborizations in the lateral and/or medial protocerebrum, which receive terminations of efferent neurons of the mushroom body and from which premotor descending neurons originate. The remaining four neurons were bilateral neurons that connect lateral accessory lobes or dorsal protocerebrums of both hemispheres. We suggest that the mushroom body of the ant participates in the processing of alarm pheromones. Seventeen (40%) of 42 neurons exhibited responses to nonpheromonal odors, indicating that the pheromonal and nonpheromonal signals are not fully segregated when they are processed in the protocerebrum. This may be related to modulatory functions of alarm pheromones, i.e., they change alertness of the ant and change responses to a variety of sensory stimuli.