Analysis of facial displays and verbal report to assess subjective state in the non-invasive detection of limbic system activation by procaine hydrochloride.

The problem of scalp EEG as a measure of cortical or subcortical activity is particularly relevant to complex partial seizures as the abnormal discharging is frequently limbic in origin [14, 30]. Livingston [38] has suggested that administration of intravenous procaine as a limbic activator and cortical suppressor would be of utility in diagnosing limbic involvement in complex partial seizures. While there is considerable evidence derived from experimental animal models that procaine hydrochloride is a limbic system activator that acts preferentially on subcortical epileptic foci at lower doses than on less active epileptic foci or non-epileptic tissue [2, 4], it was necessary to demonstrate that procaine activates the human limbic system. The non-invasive approach taken in the present study was to compare the published effects of direct electrical stimulation of the human limbic system [31] to the behavioural and subjects effects of intravenous procaine administration. The areas in which we obtained the most robust procaine effects (hallucinations, emotions and alimentary sensations) were also Halgren et al.'s [31] most repeatable effects. The correspondence between electrical stimulation effects and procaine administration effects was striking - with verbal report by patients matching exactly in many instances. Furthermore, analysis of facial displays proved useful in providing access to subjects state fluctuations which would otherwise have gone undetected. The data provide strong evidence that procaine hydrochloride can be used as a human limbic system activator. Future research will investigate the clinical and diagnostic significance of differential response to procaine.

The GABA/benzodiazepine receptor-chloride ionophore complex: nature and modulation.

1. A high affinity, saturable, stereospecific binding site for Benzodiazepines has been found to be functionally and possibly structurally related to a GABA receptor-chloride ionophore complex. 2. There are both central (CNS) as well as "peripheral" binding sites, involving multiple organs. 3. Evidence strongly suggests that mutually exclusive Benzodiazepine agonists and antagonists bind to the same receptor, possibly in an agonist-antagonist-inverse agonist continuum. 4. The search for an endogenous ligand has been inconclusive and the question of such a substance remains open. 5. Although the relationship between this receptor and the Limbic System remains unclear, it seems certain that the Benzodiazepine receptor plays an important role in the modulation of Limbic System excitability.