Fra. Cagampang et al., Adrenomedullectomy prevents the suppression of pulsatile luteinising hormone release during fasting in female rats, J NEUROENDO, 11(6), 1999, pp. 429-433
Fasting inhibits the pulsatile secretion of luteinising hormone (LH) in fem
ale rats, an effect which is potentiated by the presence of oestradiol (E-2
). We have previously described various pharmacological or surgical treatme
nts that can rapidly restore the pulses in a fasting animal. Nevertheless,
the central and peripheral mechanisms that mediate this suppression of the
pulses remain unclear. We have recently shown that adrenomedullectomy preve
nts the suppression of LH pulses by insulin-induced hypoglycaemia, a state
which activates the sympathoadrenal axis. The present study was undertaken
to establish whether this axis might contribute to the loss of the pulses t
hat occurs in ovariectomised E-2-treated rats that have been fasted for 48
h. Following sham adrenomedullectomy LH pulses were observed in animals fed
ad libitum; after 48 h of fasting the animals that had received this sham
procedure showed a significant suppression of LH levels and LH pulse freque
ncy. In contrast, adrenomedullectomy prevented the inhibition of the pulses
by 48 h of fasting; it had no effect on the pulses in the absence of fasti
ng, These results suggest that adrenomedullary activity plays a significant
role in the fasting-induced suppression of LH pulses in rats.