| dc.description.abstract |
The aim of the present study was to determine whether leptin might play a rolein the gonadotrophic response of mature merino rams to changes in the level ofnutrition in rams fed ad libitum. Recombinant bovineleptin was infused intracerebroventricularly and voluntary food intake (VFI)and luteinizing hormone (LH) pulse frequency were measured. In Experiment 1,rams (n = 5) were infused for 24 h per day for 5days with vehicle or with leptin (0.04, 0.4 and 4.0g h<emph type="7">-1 ). All doses decreased both VFI and LH pulsefrequency. In Experiment 2, rams were infused for 24 h per day for 5 days withvehicle (n = 10) or leptin (4 g h<emph type="7">-1; n= 5); asub-group of 5 controls was pair-fed to the leptin-infused group to controlfor effects of changes in feed intake. LH pulse frequency was reduced equallyin both the leptin-infused and pair-fed groups. Leptin did not affect othersystems controlled by the hypothalamic-pituitary axis. Thus, rather thanstimulate LH secretion, intracerebral leptin specifically inhibits it byreducing food intake, so it is unlikely that effects of nutrition on thereproductive axis in mature rams involves leptin as a single blood-bornesignal. A range of nutritional or metabolic inputs may be needed, and perhapsinterconnections between neural centres that control appetite andreproduction. |
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