Ionic currents in cultured supraoptic neurons: actions of peptides and transmitters

The hypothalamo-neurohypophysial system has proved an excellent model for peptidergic neurons in the central nervous system. Electrophysiological studies using in vivo and in vitro preparations with extracellular and intracellular recording techniques have determined some of the intrinsic and extrinsic mechanisms that generate the striking firing patterns that the neurons exhibit. We have developed a dissociated cell preparation of these neurons and used patch clamp recording techniques to enable detailed studies of membrane properties underlying such activities. Cultured neonatal supraoptic neurons fired spontaneous action potentials which in some cells were distinctively patterned. Under voltage clamp, voltage-activated Na+, K+, and Ca2+ currents were recorded. K+ and Ca2+ currents were modulated by application of alpha-adrenergic agonists, and Ca2+ currents were also modulated by kappa-opioid agonists. The neurons were also sensitive to gamma-aminobutyric acid which acted directly on Cl- channels. Spontaneous, patterned activity, the presence of functional receptors for neurotransmitters and the ability to study the neurons under voltage clamp suggest that this is an excellent model system for studying these peptidergic neurons.