Abstract
Neurosecretory neurons have been identified in the rat supraoptic nuclei (SON) by their antidromic response to stimulation of the neurohypophysis. This study was undertaken to determine the effects of i.v. injection of morphine (1 mg/kg), ketamine (1 mg/kg), ketamine (10 mg/kg), and methohexital (2 mg/kg) on the unit activity of antidromically identified neurohypophysial neurosecretory neurons in 33 rats.
Ten units tested were all inhibited by morphine (1 mg/kg), and the effect of morphine on 4units were completely antagonized by naloxone (40 μg/kg) . Five out of 8 units tested were inhibited by ketamine (1 mg/kg), but the remaining 3 units did not change. Ketamine (10 mg/kg) reduced the firing rate of all 7 units and methohexital (2 mg/kg) also depressed spontenous firing rate of all 8 units tested in the SON.
These results of the present study suggest that morphine, ketamine and methohexital may suppress the release of antidiuretic hormone (ADH) from the neurohypophsis.
