Periventricular preoptic area neurons coactivated with luteinizing hormone(LH)-releasing hormone (LHRH) neurons at the time of the LH surge are LHRHafferents
Ww. Le et al., Periventricular preoptic area neurons coactivated with luteinizing hormone(LH)-releasing hormone (LHRH) neurons at the time of the LH surge are LHRHafferents, ENDOCRINOL, 140(1), 1999, pp. 510-519
Earlier studies demonstrated coactivation of the periventricular preoptic a
rea (pePOA) with LHRH neurons at the time of an induced or spontaneous LH s
urge, suggesting that the pePOA might regulate LHRH neurons. To investigate
this hypothesis, studies were conducted to determine the temporal pattern
of pePOA Fos activation during the rat estrous cycle and establish the conn
ections of the pePOA neurons with LHRH neurons. Fos activation within LHRH
and pePOA neurons showed the same temporal pattern. Both were absent during
diestrous I, diestrous II, and the morning of proestrus. Fos was induced i
n the pePOA and LHRH neurons beginning on the afternoon of proestrus (4 h b
efore lights off), with a decline 8 h later on proestrous evening. Tract-tr
acing studies then established the relationship between LHRH and pePOA neur
ons. Retrograde labeling with fluorogold determined that a portion of the F
os-positive pePOA neurons present at the time of the LW surge sent a projec
tion to regions that contain LHRH cells, Anterograde tracer (neurobiotin) i
njections established that the pePOA neurons sent axone to the LHRH cells.
Taken together, these data indicate that the pePOA provides direct input to
LHRH neurons that is likely to stimulate LHRH neurons at the time of the L
H surge.