pituitrin and eticlopride

Syrian hamsters exposed to anabolic/androgenic steroids (AAS) during adolescence consistently show increased aggressive behavior across studies. Although the behavioral and anatomical profiles of AAS-induced alterations have been well characterized, there is a lack of data describing physiological changes that accompany these alterations. For instance, behavioral pharmacology and neuroanatomical studies show that AAS-induced changes in the vasopressin (AVP) neural system within the latero-anterior hypothalamus (LAH) interact with the serotonin (5HT) and dopamine (DA) systems to modulate aggression. To characterize the electrophysiological profile of the AAS aggression circuit, we recorded LAH neurons in adolescent male hamsters in vivo and microiontophoretically applied agonists and antagonists of aggressive behavior. The interspike interval (ISI) of neurons from AAS-treated animals correlated positively with aggressive behaviors, and adolescent AAS exposure altered parameters of activity in regular firing neurons while also changing the proportion of neuron types (i.e., bursting, regular, irregular). AAS-treated animals had more responsive neurons that were excited by AVP application, while cells from control animals showed the opposite effect and were predominantly inhibited by AVP. Both DA D2 antagonists and 5HT increased the firing frequency of AVP-responsive cells from AAS animals and dual application of AVP and D2 antagonists doubled the excitatory effect of AVP or D2 antagonist administration alone. These data suggest that multiple DA circuits in the LAH modulate AAS-induced aggressive responding. More broadly, these data show that multiple neurochemical interactions at the neurophysiological level are altered by adolescent AAS exposure.

Topics: Action Potentials; Aggression; Anabolic Agents; Animals; Dopamine D2 Receptor Antagonists; Hypothalamic Area, Lateral; Hypothalamus, Anterior; Male; Mesocricetus; Neurons; Receptors, Dopamine D2; Salicylamides; Serotonin; Steroids; Vasopressins

In pubertal male Syrian hamsters, exposure to anabolic/androgenic steroids (AAS) during adolescence facilitates a high level of offensive aggression modulated by the enhanced development and activity of the vasopressin (AVP) and dopamine (DA) neural systems within the latero-anterior hypothalamus (LAH), that is, a brain region implicated in the control of aggression. The present studies provide a detailed report of the pharmacologic interactions between AVP and DA D2 receptor signaling within the LAH in the control of adolescent AAS-induced offensive aggression. Male Syrian hamsters were treated with AAS throughout adolescence and tested for aggression after local infusion of the DA D2 receptor antagonist eticlopride (ETIC) alone, or in combination with AVP in the LAH in an effort to determine the influence of DA D2 receptors relative to AVP-receptor mediated aggression mechanisms. As previously shown, ETIC infusion into the LAH suppressed adolescent AAS-induced aggressive responding; however, the AAS-induced aggressive phenotype was rescued by the coinfusion of AVP into the LAH. These behavioral data indicate that interactions between AVP and DA neural systems within the LAH modulate the control of aggression following adolescent exposure to AAS and that DA D2 receptor signaling functions upstream of AVP in the LAH to control this behavioral response.

Topics: Aggression; Anabolic Agents; Androgens; Animals; Dopamine Antagonists; Hypothalamus; Male; Mesocricetus; Salicylamides; Vasopressins