HYPOTHALAMO-HYPOPHYSIAL CONTROL OF OVULATION IN THE VOLE (MICROTUS AGRESTIS)

Hypthalamohypophysial control of ovulation in the vole (Microtus agrestis) was studied. Adult virgin female voles were stimulated electrically in different regions of the hypothalamus received injections of sheep median eminence extracts into the suborbital canthal sinus or received iv or ip injections of varying doses of luteinizing hormone (LH). More animals ovulated following anterior hypothalamic stimulation than midhypothalamic stimulation (p less than .05). 6 of 12 stimulated in the anterior region had Graafian follicles present whereas those stimulated in the other 2 regions invariably had Graafian follicles when sacrificed 24 hours later. 13 of 18 which received the median eminence extract ovulated and all had Graafian follicles at autopsy. 1.2 mcg LH stimulated ovulation in all animals but 1 while 2.5 and 5 mcg did so in all but 2 in each group. 3 of 6 given .6 mcg LH ovulated and none did so if .3 mcg or less was administered. Graafian follicles were invariably present. Iv injections gave results similar to those of ip injections. These results indicated that next to mating anterior hypothalamic stimulation is the most potent ovulation stimulus.