We have emitted the hypothesis that the double-way effect is possible not only due to the wide range of receptor substrates and receptor subtypes but it can manifest at the heterosynaptic and synaptic cotransmission level as a consequence of the informational unbalance which very low or very high doses of biological signals (in pathological disorders) or of drug signal (agonist or antagonist) can do on physiological balance between both two coupled synaptic systems. To verify this hypothesis we choosed as place of manifesting and observing of the phenomen the informational gearing between the endogenous opioid system as "modulator" and the catecholaminergic systems as "alarm". As drug signals we used naloxone (NALX) and clonidine (CLON). The function studied to reveal the double-way effect was stress analgesia monitored in the classical test of te "hot plate". The experimental stress was induced to the mouse by submitting to forced swimming using the "despair test". In the work are presented the dose-effect curves and inflexion points which mark the changing of the sense of the effect.