Abstract
Supraoptic neurosecretory neurons express a prominent N-methyl- d-aspartate receptor system. Recent in vitro evidence reveals that N-methyl- d-aspartate receptor activation dramatically alters the spontaneous discharge patterns of supraoptic neurons. In this study we evaluate whether N-methyl- d-aspartate receptors in vivo contribute to the development of characteristic phasic discharge patterns displayed by vasopressin-secreting neurons. Intravenous administration of ketamine hydrochloride, a non-competitive N-methyl- d-aspartate receptor antagonist, was used to examine whether N-methyl- d-aspartate receptor blockade influences patterned spontaneous discharge observed in supraoptic neuro-secretory neurons. Extracellular recordings were obtained from identified hypothalamic supraoptic neurons in pentobarbital-anaesthetized Long-Evans rats. Systemic administration of ketamine (≤1.5 mg/kg) potently suppressed spontaneous phasic discharge in 16/19 putative vasopressin-secreting cells. The ketamine-induced blockade was dose dependent, fully reversible and was associated with the complete blockade of activity evoked by local pressure application of N-methyl- d-aspartate, but not the activity evoked by α-amino-3-hydroxy-5-methyl-isoxazole-4-propionate receptor agonists (6/6 cells). Ketamine had no detectable effect on threshold or shape of antidromic action potentials. By comparison, the activity in 9/10 continuously active neurons (putative oxytocin-secreting) was unaffected by administration of identical doses of ketamine. These data suggest that N-methyl- d-aspartate receptors play an important role in regulating the onset and maintenance of spontaneous phasic activity patterns displayed by rat supraoptic vasopressin neurons in vivo.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call