Comparison between hypothalamic multiple-unit activity and corticotropic function after bilateral destruction of the hippocampus

Multiple unit activity (MUA) was recorded from the adrenocorticotropic area (n. posterior medialis hypothalami, PMH) of unrestrained resting pigeons throughout the 24 h period and compared with plasma corticosterone levels (B). Bilateral electrolytic lesions of the hippocampus suppressed diurnal variations of MUA and B. Both parameters were stabilized at a steady high level whereas complete neural isolation of the basal hypothalamus led to stabilized intermediate plasma B level and MUA pattern.