Behavioral assessment of norepinephrine and serotonin function and interaction in the hippocampal formation.
Norepinephrine (NE) and serotonin (5-HT) were injected either into the dorsal or ventral hippocampal formation of rats in doses ranging from 0.005 microgram/microliter to 5.0 microgram/microliter. Behavioral reactivity was assessed by recording latency to paw lick when placed on a hot plate and magnitude of force displaced in a vertical direction to a footshock. In addition open field activity was measured. NE injections resulted in a dose-dependent increase in behavioral reactivity to the hot plate and footshock; 5-HT injections resulted in a dose-dependent decrease in behavioral reactivity to hot plate and footshock. Both NE and 5-HT injections resulted in a dose-dependent increase in open field activity. NE injections were more effective in increasing reactivity when injected into the dorsal hippocampus while 5-HT injections were more effective in decreasing behavioral reactivity when injected into the ventral hippocampus. Both NE and 5-HT were most effective in increasing open field behavior, however, when injected into the dorsal hippocampus. When NE and 5-HT were injected simultaneously they resulted in no change in behavioral reactivity as compared to saline injections. Simultaneous injections of NE and 5-HT neither enhanced nor antagonized the increase in open field activity of each amine injected alone. The results are discussed in terms of the functional significance of NE and 5-HT in the hippocampus, their modes of action and significance for understanding dorsal-ventral hippocampal differences.
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D006624:Hippocampus / Q000033:anatomy & histology / Q000502:physiology*; D007267:Injections; D009638:Norepinephrine / Q000008:administration & dosage / Q000502:physiology*; D051381:Rats; D011930:Reaction Time / Q000187:drug effects; D012701:Serotonin / Q000008:administration & dosage / Q000502:physiology*
D012701:Serotonin; D009638:Norepinephrine