Effect of mating on the metabolic activity of the brain and pituitary gland assessed by [C]2-deoxyglucose in a reflex ovulator, the vole (Microtus agrest s)

The neural pathways involved in reflex ovulation in the vole (Microtus agrestis) have been investigated with the [¹⁴C]2-deoxyglucose (2-DG) method. Female voles were injected i.p. with 2-DG and either not mated, sham-mated (mounted by males but vagina was taped) or mated for a period of 45 min after the injection, after which the animals were decapitated. The brain was processed for autoradiography and the relative metabolic activities (rma) of selected areas of the brain and pituitary gland were determined. The plasma separated from trunk blood was assayed for the concentration of luteinizing hormone (LH). The lordosis quotients (LQ) were (mean ± S.E.M.) 81 ± 8 (n = 5) in mated compared with 47 ± 8 (n = 5) in sham-mated voles. The rma of the midbrain central grey (CG) and reticular formation (RF) were significantly greater in mated and sham-mated voles compared with the values in unmated voles. There were no other between-group differences in the rma of the other 28 areas of the brain or pituitary gland studied in spite of the fact the plasma LH concentration in mated voles was 36.9 ± 9.6 ng NIH-LH-S18/ml compared with undetectable (< 2.5 ng/ml) values in all the sham-mated and unmated animals. These results show that in the vole increased metabolic activity of the CG and RF is associated with lordosis, but that the reflex release of LH is not accompanied by any significant change in the metabolic activity of the brain or the pituitary gland.