Research ArticleBEHAVIOR ECOLOGY

Adding up the odds—Nitric oxide signaling underlies the decision to flee and post-conflict depression of aggression

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Science Advances  13 Mar 2015:
Vol. 1, no. 2, e1500060
DOI: 10.1126/sciadv.1500060
  • Fig. 1 The NO/cGMP signaling pathway reduces the expression of aggression in socially naïve crickets.

    (A) Pictogram illustrating the site of actions of the drugs. Activators (red): SNAP, an NO donor; 8Br-cGMP, a tissue-permeable analog of cGMP. Inhibitors (blue): LNAME, an NO synthase (NOS) inhibitor; PTIO, an NO scavenger; ODQ, an irreversible inhibitor of soluble guanylyl cyclase (sGC). (B and C) Bar charts comparing the level of aggression and fight duration, respectively, for size-matched, socially naïve contestants that were both treated with NO/cGMP activators (red bars: SNAP and 8Br-cGMP), inhibitors (blue bars: PTIO, LNAME, LNAME + PTIO, and ODQ), and separate appropriate controls (gray bars: Ringer-a, b, c, DNAME, and DMSO, respectively). Circles, median; bars, interquartile range (IQR); n on x axis in (B) gives the number of contests. Significant differences to control groups are indicated by asterisks (U test, *P < 0.05, **P < 0.01, ***P < 0.001; exact P values given in text).

  • Fig. 2 The NO/cGMP pathway mediates depressed expression of aggression after social defeat.

    Bar charts comparing the level (left) and duration (right) of aggressive interactions between losers matched against their previous victors at different times after defeat (different animals for each time slot; circles, median; bars, IQR; n is given on left x axes). (A and B) Each pair of contestants was drug-treated before the initial (first) contest (cf. Fig. 1): (A) NO/cGMP activators (red bars: SNAP and 8Br-cGMP) and (B) inhibitors (blue bars: LNAME and ODQ). The effect of each drug is compared to its appropriate control (gray bars: Ringer-a for SNAP, Ringer-b for 8Br-cGMP, DNAME for LNAME, and DMSO for ODQ). Significant differences are indicated by asterisks (U test, *P < 0.05, **P < 0.01, ***P < 0.001).

  • Fig. 3 NO translates the effect of the opponent’s agonistic signals to promote the decision to flee.

    (A) Effect of the NO/cGMP pathway activator SNAP (red and gray bars: Ringer) on a contestant’s aggressiveness when matched against opponents that received no drug (top, level; middle, duration; bottom, win chances; circles, median; bars, IQR; n is given on top x axis). As depicted from left to right, one or both contestants received either no further treatment or a handicap to impede transmission/perception of agonistic signals: None# versus none, Blind# versus none, Blind# versus disarmed (none, no handicap; blind, blackened eyes; disarmed, immobilized mandibles; # denotes drug/vehicle-treated contestant). (B) As for (A), but showing the effect of the NO/cGMP pathway inhibitor LNAME (blue bars) compared to its inactive enantiomer (DNAME, gray bars). Handicaps, from left to right: None# versus none, Disarmed# versus none, Disarmed # versus blind. Significant differences between drug-treated and control groups are indicated by asterisks (U test for level and duration, χ2 test for win chances compared to controls: *P < 0.05, **P < 0.01, ***P < 0.001). Note that SNAP reduces the win chances of blind and LNAME increases win chances of disarmed, without any significant effect on escalation level and fight duration.

  • Fig. 4 The susceptible period in winners and its dependence on NO.

    (A) Bar charts showing the aggressiveness of untreated winners matched against standard hyper-aggressive opponents at different times after winning (top, level; middle, duration; bottom, win chances; different animals for each time slot). (B) As for (A) showing the effect of inhibiting NOS on winner performance against standard hyper-aggressive opponents (blue bars, LNAME; gray bars, DNAME). Significant differences are indicated by asterisks [level and duration in (A): U test, Bonferroni correction to α for three comparisons: *P < 0.025, **P < 0.005; in (B): U test: *P < 0.05, **P < 0.01; win chances: χ2 test compared to 50%: *P < 0.05, **P < 0.01].

  • Fig. 5 Susceptibility of winners to aversive stimulation and its dependence on NO.

    (A) Bar charts showing aggressiveness of winners matched against standard hyper-aggressive opponents 10 min after a previous win that received either 0, 1, or 2 successive aversive stimuli (wind puff to cerci) during the susceptible period immediately after winning (different animals for each time slot). Top, level; middle, duration; bottom, win chances. (B) Bar charts, as in (A), showing the effect of two aversive stimuli delivered at 0, 3, or 10 min after winning. (C) Bar charts, as in (B), for winners that were given two aversive stimuli and treated with either LNAME (blue bars) or DNAME (gray bars). Significant differences are indicated by asterisks [level and duration in (A) and (B): U test, Bonferroni correction to α for three comparisons: *P < 0.025, **P < 0.005, ***P < 0.0005; in (C): U test, win chances: χ2 test compared to 50%: **P < 0.01, ***P < 0.001]. Note that LNAME abolishes the effectiveness of the aversive stimulus to induce submissive behavior.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Stereotyped levels of escalating aggression in male crickets.
    • Fig. S2. Summary of effects of nitrergic drugs on loser recovery.

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