Stress and its timing: critical factors in determining the consequences of dopaminergic agents.
Dopaminergic agonists and antagonists can have opposite effects, depending on the state of the organism involved. The importance of prior state in determining the consequences of treatment with dopaminergic agents is illustrated in Serra's recent experiments. Although repeated treatment with DA antagonists enhanced the hypokinetic effects of 10 micrograms/kg of apomorphine, they obviated the influence of 25 micrograms/kg. In the former case, chronic DA-receptor blockade induced supersensitivity of DA autoreceptors; in the latter it resulted in subsensitivity. Since autoreceptor subsensitivity typically occurs after repeated treatment with DA agonists these experiments illustrate that neuroleptics caN behave like DA agonists. We discuss these and similar studies, emphasizing the role of stress and time in determining the consequences of dopaminergic agents.
D000818:Animals; D001921:Brain / Q000503:physiopathology; D004298:Dopamine / Q000031:analogs & derivatives* / Q000502:physiology*; D018492:Dopamine Antagonists; D006801:Humans; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D013312:Stress, Physiological / Q000503:physiopathology*; D013997:Time Factors
D018492:Dopamine Antagonists; D004298:Dopamine; D009638:Norepinephrine