Effect of hypothalamic injections of 5,7-dihydroxytryptamine on elicitation of mouse-killing in rats.
An overall and marked serotonin (5-HT) depletion of the brain was found to facilitate initiation of mouse-killing behavior in the rat, whereas more selective 5-HT depletions within forebrain structures such as the septum, hippocampus, cingular cortex and amygdala, did not have such an effect. In order to further investigate the topography of the 5-HT pathways and terminals though to be involved in an inhibitory control over this behavior, localized lesions of the serotonergic system(s) were performed by means of bilateral 5,7-dihydroxytryptamine (5,7-DHT) injections (5 microgram/microliter) into the hypothalamus in naive rats. 5,7-DHT injections into the medial hypothalamus did not affect the initiation of mouse-killing behavior, whereas the reflexive startle responses to air puffs were increased. The animals' open-field behavior remained unchanged. Forebrain 5-HT content was reduced by 50% in this group. 5,7-DHT injections into the lateral hypothalamus increased the proportion of killers to 46% as compared to 10% in the control group, in spite of a reduced activity in the open-field and unchanged startle responses. Forebrain 5-HT content was reduced by 88%. As the lateral hypothalamus contains afferents from both the dorsal and the median raphe nuclei, it is likely that 5-HT terminals modulate some hypothalamic mechanism involved in the control of mouse-killing behavior.
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000374:Aggression / Q000187:drug effects*; D000818:Animals; D004102:Dihydroxytryptamines / Q000494:pharmacology*; D006801:Humans; D007026:Hypothalamic Area, Lateral / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects*; D007033:Hypothalamus, Middle / Q000187:drug effects; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects; D013216:Reflex, Startle / Q000187:drug effects; D012701:Serotonin / Q000378:metabolism
D004102:Dihydroxytryptamines; D011985:Receptors, Serotonin; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin