Prolonged inhibition in burst firing neurons: synaptic inactivation of the slow regenerative inward current.

By using voltage clamping and microiontophoretic techniques, it has been found that the prolonged cholinergic and dopaminergic inhibition seen in Aplysia burst firing neurons occludes the inward current on which slow oscillations depend. It also mimics the temperature and ionic sensitivity of that inward current. This prolonged inhibition, which cannot be inverted and is insensitive to extracellular potassium changes, thus appears to result from a synaptically produced inactivation of the regenerative slow inward current underlying bursting.

Slow and rapid responses to CW and pulsed microwave radiation by individual Aplysia pacemakers.

Specific absorption rates (SARs) of microwave energy that altered firing rates were determined for individual pacemaker neurons in the abdominal ganglion of Aplysia californica. A stripline apparatus provided both for artifact-free recording of transmembrane potentials and for precise determination of the rate of absorption of microwave energy. Exposure for two to three minutes at an SAR of only a few mW/g was capable of changing the firing rate of some pacemakers.

Biochemical effects of baclofen (beta-parachlorophenyl-GABA) on the dopamine and the noradrenaline in the rat brain.

Baclofen (beta-parachlorophenyl-GABA) caused an increase in the concentration of dopamine in the rat brain with a maximum of about 170% of the control value after 1 hr and after doses of 50 mg/kg or more intraperitoneally. The alpha-methyltyrosine-induced disappearance of dopamine was inhibited to about the same extent in the corpus striatum and in the limbic system by baclofen. The accumulation of DOPA following decarboxylase inhibition was stimulated more in the corpus striatum than in the limbic system by baclofen, thus accounting for the fact that the concentration of dopamine was elevated about three times as much in the corpus striatum as in the limbic system.

Direct dopaminergic action of lisuride hydrogen maleate, an ergot derivative, in mice.

Lisuride hydrogen maleate induced stereotyped behaviour in normal as well as in reserpinized mice. It antagonized the motor depression and hypothermia induced by reserpine. On i.

Electrophysiological basis for the spatial dependence of the inhibitory coupling in the Limulus retina.

A technique for measuring, with total optical isolation, the inhibition between two individual receptor units in the Limulus lateral eye is described. The extracellular responses of pairs of units were recorded, using light piping microelectrodes. The inhibitory coupling between two units was found to be nonlinear and describable by a simple hyperbolic equation written in terms of saturation rate (S), half saturation (H), and threshold (ft).

Negative resistance characteristic essential for the maintenance of slow oscillations in bursting neurons.

Voltage clamping giving step commands reveals a steady-state negative resistance characteristic in the current-voltage curves of Aplysia bursting neurons. This is observed below spike threshold in the unstable range through which the membrane potential slowly oscillates. The negative resistance characteristic underlies this instability and shapes the rapid depolarization-hyper-polarization phase of the cycle.

A direct synaptic connection mediating both excitation and inhibition.

Neurons have generally been thought to produce only one synaptic action on any particular cell which they innervate. An identified interneuron in the abdominal ganglion of Aplysia mediates both direct excitation and inhibition to an identified follower cell. At low firing rates the interneuron produces excitatory postsynaptic potentials; however at higher firing rates these gradually diminish in size and eventually invert to inhibitory postsynaptic potentials.