Unit Activity Responses Research Articles

The analysis of inter-spike interval fluctuation of hypothalamic unit activity in response to luteinizing hormone and oxytocin.

Non-anesthetized ovariectomized cats were employed for recording hypothalamic unit activity. The discharge pattern of the neurones which responded to blood LH or oxytocin were analyzed from statistical view-point.1. The pulse train of neuronal activity was analyzed into discharge interval histogram. In addition the statistical dependency between mean discharge interval and standard deviation was calculated. In three fourths of the hypothalamic neurones the discharge activity showed exponential or gamma type distribution of discharge interval and the rest showed either normal, Poisson or unclassified distribution. In the control condition the coefficient of regression was between 0.9 and 1.4 and the linearity was good. Although no essential difference existed in the distribution of inter-spike interval between estrus and anestrus, an increase in the discharge rate was observed in anterior hypothalamic neurones and a decrease in LH neurones.2. Both at estrus and anestrus LH administration caused mean discharge interval of the anterior hypothalamic neurones to decrease and of the VMH neurones to increase. The change in discharge interval by LH at anestrus was accompanied by an increase in standard deviation and the same mean-SD relationship was kept as before administration.On the other hand LH administration at estrus resulted in deviation of mean-SD relation from the regression line of the control condition. The latter type of change could be observed in a few neurones of unclassified distribution in the VMH and AHA.3. By oxytocin administration at anestrus the discharge rate of AHA and LHA neurones increased and of VMH neurones decreased. On the contrary at estrus oxytocin injection caused discharge rate of lateral hypothalamic neurones to decrease and of ventromedial hypothalamic neurones to increase. In the majority of these cases, the change could be plotted on an extension of mean-SD regression line obtained before administration. But there were a few neurones which showed a deviation downward from the control regression line. This type of change was observed only in neurones of unclassified distribution.Discussion was made on the mechanisms underlying the changes in hypothalamic neuronal activity induced by administration of LH and oxytocin.