Hitoshi Miyazawa's research while affiliated with National Center of Neurology and Psychiatry and other places

The lateral hypothalamic area (LHa) is involved in various functions such as feeding, drinking, sexual and reward behavior, among others. Recently, we demonstrated that the LHa can regulate cellular immunity in the spleen. In experiments involving the LHa, it was noticed that the spleen shrinks noticeably after LHa destruction. To explore this phenomenon further, the effect of LHa lesioning on splenocyte apoptosis was investigated. Male Wistar-King-Aptekman rats underwent bilateral lesioning of their LHa and consequent spleen weights, splenocyte numbers and apoptosis were measured. For the detection of splenocyte apoptosis, both ELISA, which measures DNA fragmentation within the splenocytes, and flow cytometry, which measures the percentage of apoptotic lymphocytes in the spleen, were used. In the LHa-lesioned rats, spleen weights and the number of splenocytes decreased significantly within 24 h. Additionally, in the spleen, lymphocyte apoptosis significantly increased compared to the control after 6 h. These results suggest that the LHa may play a role in immunoregulation by affecting lymphocytes in the spleen through apoptosis and may be relevant to the pathway of stress-induced apoptosis.

Natural killer cell (NK) activity in WKA and SD rats was found to be significantly higher following electrical stimulation of the lateral hypothalamus (LH) compared to sham operated. There was no such difference between sham operated rats and those receiving electrical stimulation in the frontal cortex as a control. Operations were performed under sodium pentobarbital anesthetic, and NK activity against YAC-1 target cells was measured 20 h later using 51Cr release assay. The LH area stimulated is a potent reward center and that stimulation of this point increased NK activity opens the possibility that pleasure might play a role in cellular immunity.