Jy. Summylong et al., CROSSTALK IN THE MAGNOCELLULAR SYSTEM DURING OSMOTIC STIMULATION OF ONE SUPRAOPTIC NUCLEUS, Brain research bulletin, 33(6), 1994, pp. 645-654
Neural connections linking the four magnocellular nuclei, i.e.,. the p
aired supraoptic (SON) and paraventricular (PVN) nuclei, may contribut
e to the simultaneous and parallel changes in firing patterns of oxyto
cinergic neurons during reflex milk ejection. To investigate these neu
ral connections in the absence of suckling, intranuclear release of ox
ytocin (OT) was stimulated by microdialysis of hypertonic CSF containi
ng 1 M NaCl (HS-CSF) into the right SON area and glucose metabolism of
both SONs and PVNs and the neural lobe of virgin and lactating (10-12
day) rats was mapped by the autoradiographic [C-14]deoxyglucose (DG)
method. OT in the microdialysates and in plasma, obtained before and a
fter 80-90 min of dialysis with CSF or HS-CSF, was quantified by RIA.
In both virgin and lactating rats, microdialysis of HS-CSF unilaterall
y into the SON area significantly (p < 0.05) increased release of OT i
n the nucleus and into plasma, which was associated with enhanced (p <
0.05) metabolic activity in the ipsilateral and contralateral SON and
the neural lobe but not in either PVN. Compared with virgins, lactati
ng rats were less active, had lower (p < 0.05) glucose utilization in
the hypothalamo-neurohypophysial system, and less (p < 0.05) OT in pla
sma during microdialysis of HS-CSF into the SON area. The osmotic stim
ulus did not activate neural structures (suprachiasmatic and medial am
ygdaloid nuclei) near the SON in either hemisphere. Thus, neural conne
ctions or, less likely, transport of OT via the subarachnoid space, ma
y function to recruit activation of cells in the contralateral SON fol
lowing hypertonic stimulation of cells in the other SON.