SOMATIC AFFERENT REGULATION OF PLASMA PROLACTIN IN ANESTHETIZED RATS

The effects of noxious and non-noxious mechanical stimulation of vario us segmental skin areas (face, forelimb, abdomen, and hindlimb) on the plasma concentrations of prolactin (PRL) were examined in anesthetize d rats. The experiments were performed on urethane-anesthetized female Wistar rats, ventilated artificially, on the day of estrus. Blood sam ples (0.5 ml) were collected from the femoral artery every 20 min. Pla sma concentrations of PRL were determined by radioimmunoassay. Noxious mechanical stimulation was delivered by pinching the skin with a surg ical clamp, while non-noxious mechanical stimulation was delivered by brushing the skin with a toothbrush. Pinching the hindpaw for 6 min si gnificantly increased plasma PRL concentration during stimulation to a bout 280% of the prestimulation value (p < 0.05). Pinching the face, t he forepaw or the abdomen had no significant effect. Brushing of any s kin area for 6 min did not significantly change plasma PRL concentrati ons. These results indicate that cutaneous, nociceptive sensory inform ation contributes to the reflex regulation of PRL secretion from the a nterior pituitary when emotional factors are eliminated by anesthesia, and this effect is highly dependent on the site of stimulation.