Hormones and behavior
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Hormones and behavior · Mar 1994
Regulation of territorial behavior in the sedentary song sparrow, Melospiza melodia morphna.
Male song sparrows (Melospiza melodia morphna) of western Washington State show year-round territoriality. Although territorial aggression during the breeding season was accompanied by high circulating levels of luteinizing hormone (LH) and testosterone (T), similar aggression in the non-breeding season occurred when gonadal hormone levels were basal. Experimental removal of territorial males in autumn resulted in new males taking over the territory within a few days. ⋯ In contrast, males exposed to STI in autumn showed a strong aggressive response during the challenge, but then territorial aggression abated rapidly when the stimuli were withdrawn. Implants of T into males in autumn reinstated the high level of aggression after withdrawal of STI in a manner similar to that seen during the breeding season. These data suggest that in M. m. morphna T does not activate territorial aggression per se, but may increase the intensity of an aggressive response to STI, and persistence of the behavior after STI is withdrawn.
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Hormones and behavior · Dec 1993
Treatment with an anabolic-androgenic steroid affects anxiety-related behavior and alters the sensitivity of cortical GABAA receptors in the rat.
The putative psychotropic effect of the anabolic-androgenic steroid, testosterone propionate (TP), was determined in intact adult male rats after 1 or 2 weeks of continued exposure via subcutaneously implanted capsules. Behavior was assessed in a novel open-field arena and in the elevated plus-maze. In addition, gamma-aminobutyric acid (GABA)-stimulated 36chloride (Cl-) influx was determined in cerebral cortical synaptoneurosomes as a function of TP exposure. ⋯ Thus, 1 week of treatment with TP resulted in anxiolytic behavior that was accompanied by an increase in the sensitivity of cortical GABAA receptors. However, the behavioral and neurochemical changes were no longer present after 2 weeks of TP exposure. These results are discussed in terms of the agonist effects of reduced androgen metabolites at the GABAA receptor and the possible development of tolerance to these effects.
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Electrolytic lesions of several potential brain afferents to the spinal nucleus of the bulbocavernosus (SNB) affect the display of penile reflexes. Ablation of the median and pontine raphe areas significantly potentiates the expression of cups and flips. ⋯ Although bilateral destruction of the lateral vestibular nucleus (LVN) completely eliminated penile reflex activity, it also caused significant motor impairment thus clouding conclusions concerning the normal role of the LVN in penile reflex behavior. These and other results support the hypothesis that these brain regions which project to the SNB region normally modulate spinal reflex behavior of the rat penis.