Effects of pentobarbital on hypothalamic catecholamines and LRH activities.

Pentobarbital (Pnt) injection at 12.30 h to ovariectomized rats suppressed the LRH contents of the medial basal hypothalamus (MBH) in association with a significant fall in serum LH 60-90 min later. The LRH contents in the preoptic area (POA) were unchanged in Pnt treated rats. A similar effect on LRH levels in the MBH was also evident in ovariectomized rats pre-treated with oestradiol benzoate. Pnt administration rapidly reduced the noradrenergic (NE) turnover in the MBH and POA, whereas dopamine (DA) turnover was unaltered. These studies show that: (i) the apparent decrease in LRH secretion (release + contents) following Pnt treatment was associated with a fall in the hypothalamic NE neurotransmission, and (ii) LRH neurons and fibres in the MBH alone respond to Pnt treatment.