Adrenal Gland Weight Predicts the Satuation Level of Long-Tem Potentiation and Depotentiation in Hippocampual CA1 of Adult Female Rats

It is well known that hippocampal LTP is modulated by corticosteroids released from the adrenal glands, and the activity of adrenal glands, in turn, is influenced by hippocampal activity through the Hypothalamic-Pituitary-Adrenocortical (HPA) axis. In the present research, we studied the relationship between hippocampal plasticity and the weight of adrenal glands, an indicator for the accumulative effect of adrenal activation. In 9-month-old female rats, we measured the saturation level of LTP and subsequent depotentiation in the CA1 region of the hippocampus as well as the wet weight of the adrenal glands. The adrenal gland weight was positively correlated with the saturation level of LTP (rs=0.830, p¡0.01, n=10), but negatively correlated with the subsequent depotentiation (rs=-0.624, rs critical value=0.649). The saturation level of LTP and saturated depotentiation level negatively correlated. Although left adrenal gland is significantly larger than right side, both left and right adrenal gland weight is significantly correlated with plasticity of hippocampal CA1,indicating that neuronal plasticity is not assmetrically regulated by adrenal gland. The adrenal gland weight did not depend on the body weight. These results suggest that the function of adrenal glands may be directly involved in modulating hippocampal synaptic plasticity.