[Antidromic identification of hypothalamic neurosecretory cells which participate in the anterior pituitary control...

Attempts were made to identify hypothalamic neurosecretory cells which participate in the anterior pituitary control with a special reference to the effects of ovarian hormones. Wave forms of the antidromically activated action potentials in the hypothalamus were investigated in the female rats of Wistar strain. The animals of different endocrinological environments, that is, proestrus and diestrus-I of 4-day cyclers; ovariectomized, ovariectomized and estrogen primed, ovariectomized and progesterone primed, were used. The operational procedures were performed under light urethane anesthesia. Different two types of craniotomy were adopted for the preparation. For recordings from the medial basal hypothalamus, the ventral surface of the brain was exposed by parapharyngeal approach, and a bipolar silver ball electrode for the application of electrical stimuli was placed on the surface of the median eminence (ME). Another method was used for recordings of the medical preoptic area (MPO) and the periventricular area of the MPO and the anterior hypothalamus (PVA). In the latter, the parietal surface of the brain was exposed and a side-by-side bipolar electrode for the stimulation was inserted to the arcuate (ARC-ME region. All the recordings were performed by using glass pipettes which were filled with 0.5 M sodium acetate solution. The solution was added with pontamine sky blue 6B to allow marking recording sites. Stimulatory pulses of 5 msec duration of variable intensity were generated by an electronic stimulator and applied by the above mentioned bipolar electrodes. The antidromic responses and the intensity of the stimuli were observed and photographed on a synchroscope. ...