Modulation of the spike activity of neocortex neurons during a conditioned reflex.

Experiments were conducted on cats to study the effects of iontophoretic application of glutamate and a number of modulators on the spike activity of neurons in the sensorimotor cortex during a conditioned reflex. These studies showed that glutamate, as well as exerting a direct influence on neuron spike activity, also had a delayed facilitatory action lasting 10-20 min after iontophoresis was finished. Adrenomimetics were found to have a double modulatory effect on intracortical glutamate connections: inhibitory and facilitatory effects were mediated by beta1 and beta2 adrenoceptors respectively.

[The modulation of the pulse activity of neocortical neurons during a conditioned reflex].

Spontaneous and evoked activity of neurons in the sensorimotor cortex was recorded in cats with learned conditioned placing reaction before, during, and after the iontophoretic application of synaptically active substances. It was shown that apart from direct excitatory effect on the cortical neurons during its application, glutamate (Glu) exerted some modulatory influence on unit activity in subsequent 20 min. Noradrenaline suppressed the background and evoked activity through beta 1 adrenoreceptors.

Interaction of glutamatergic and adrenergic inputs of cortical neurons during conditioning.

Background and evoked activities of sensorimotor cortex neurons have been examined on learning cats with conditioned placing reaction before, during and after iontophoretic application of synaptically active drugs. It was shown that glutamate exerted not only a direct excitatory effect on the cortical neurons during its application, but also developed modulatory influences on background and evoked impulse activity after cessation of application in the subsequent 10-20 min. Adrenergic influences on the activity of neocortical neurons evoked by application of adrenomimetic drugs were complex and consisted of at least two different types.

Dependence of sensorimotor cortex neuron activity on noradrenergic and serotoninergic transmission in unspecific thalamic nuclei.

Background and evoked impulse activity of sensorimotor cortex neurons and conditioned reflex of trained cats were changed by blockers of noradrenaline and serotonin receptors applied through chemitrodes to thalamic complex of the centrum medianum and nucleus parafascicularis neurons. Application of obzidan, an antagonist of beta-adrenoreceptor to the complex of the centrum medianum and nucleus parafascicularis induced an initial increase and following decrease of the motor activity of cats. After obzidan application conditioned reflex remained unchanged at the initial, excitatory phase and started to decrease later.

[The effect of the selective blocking of synaptic transmission in the parafascicular complex on the neuronal activity of the sensorimotor cortex].

Peculiarities of spike responses of the sensorimotor cortex neurons and conditional activity induced by blockade of noradrenergic and serotoninergic inputs of the PF complex (CM-PF) have been studied in chronic experiments on cats with a preliminarily conditioned placing reaction to an auditory stimulus--a click. It is shown that an increase in the background activity of neurons of the sensorimotor cortex was caused by microinjections of obsidan, an adrenergic blocker, while depression--by microinjections of lysergoamid, a serotonin blocker. The effect of both blockers on the neuronal reactions evoked by conditional auditory stimulus was the same (depression).