Kinetics of the interaction of dihydroalprenolol with beta-adrenergic receptors in rat cerebral cortex

Time and temperature dependence of the binding of 3H-dihydroalprenolol (3H-DHA) to beta-adrenergic receptors in rat cerebral cortex is described. The kinetic data obtained suggest that 3H-DHA binding proceeds through a two-step reaction scheme consisting of a bimolecular association step followed by an unimolecular internal conversion of the radioligand receptor complex (isomerisation). Equilibrium thermodynamic analysis provided evidence that the over-all binding process is associated with a small decrease in enthalpy and a substantial increase in entropy. Within the framework of the two-step binding kinetics, the evaluation of the temperature dependence by the van't Hoff analysis resulted in values for thermodynamic parameters for the single equilibrium steps. The data suggest that the association step can be considered as a bimolecular hydrophobic interaction which is mainly entropy-driven due to the release of structural water, while the isomerisation step is accompanied by a large negative change in both enthalpy and entropy. The large negative change in the activation entropy for the forward reaction of the isomerisation step, obtained from evaluation of Arrhenius plots, indicates an internal conversion to a highly ordered receptor-ligand complex, while the low activation energy points to a small threshold energy for reaching this structure. Thus, these result support a previous assumption that the hydrophobic center of an adrenergic antagonist interacts with the receptor by entering a pocket (Cherksey et al. 1981).     

Neuronal mechanisms of interaction of Deiters nucleus with the cerebral cortex.

The effects of stimulation of the vestibular nerve and five different cerebral cortex areas on the neuronal activity of the lateral vestibular nucleus of Deiters were studied. Stimulation of the cerebral cortex is shown to lead to antidromic and synaptic activation of Deiters neurons. The synaptic potentials of Deiters neurons evoked from the cerebral cortex were of mono- and polysynaptic origin. In particular, stimulation of the cerebral cortex evoked in Deiters neurons mono- and polysynaptic excitatory postsynaptic potentials. Collaterals of vestibulospinal neurons reaching different cortex fields as well as convergence of influences from these cortex fields on Deiters neurons were revealed. Inhibitory effects of the cerebral cortex on Deiters neurons were of polysynaptic origin and occurred rarely. The topical correlation between Deiters nucleus and different areas of the cerebral cortex was found. The peculiarities and functional significance of the effects obtained are discussed.     

Quantum physics in neuroscience and psychology: a neurophysical model of mind-brain interaction

Neuropsychological research on the neural basis of behaviour generally posits that brain mechanisms will ultimately suffice to explain all psychologically described phenomena. This assumption stems from the idea that the brain is made up entirely of material particles and fields, and that all causal mechanisms relevant to neuroscience can therefore be formulated solely in terms of properties of these elements. Thus, terms having intrinsic mentalistic and/or experiential content (e.g. 'feeling', 'knowing' and 'effort') are not included as primary causal factors. This theoretical restriction is motivated primarily by ideas about the natural world that have been known to be fundamentally incorrect for more than three-quarters of a century. Contemporary basic physical theory differs profoundly from classic physics on the important matter of how the consciousness of human agents enters into the structure of empirical phenomena. The new principles contradict the older idea that local mechanical processes alone can account for the structure of all observed empirical data. Contemporary physical theory brings directly and irreducibly into the overall causal structure certain psychologically described choices made by human agents about how they will act. This key development in basic physical theory is applicable to neuroscience, and it provides neuroscientists and psychologists with an alternative conceptual framework for describing neural processes. Indeed, owing to certain structural features of ion channels critical to synaptic function, contemporary physical theory must in principle be used when analysing human brain dynamics. The new framework, unlike its classic-physics-based predecessor, is erected directly upon, and is compatible with, the prevailing principles of physics. It is able to represent more adequately than classic concepts the neuroplastic mechanisms relevant to the growing number of empirical studies of the capacity of directed attention and mental effort to systematically alter brain function.     

Organization of interneuron interaction in the cerebral cortex of cats learning to distinguish visual stimuli

Focal and impulse activity of neurones, recorded in pairs with one microelectrode, was studied in the field 18 of cat visual cortex, during learning of visual differentiation of shaped stimuli--light strips with different orientation one towards the other. Differences were found between functional properties of neighbouring visual neurones before learning and in learning dynamics. During learning, independently of visual signal stimuli orientation, reaction patterns of the same type were formed in neighbouring visual neurones.     

Biological nonlocality and the mind-brain interaction problem: comments on a new empirical approach

Up to now, we have been faced with an age old fundamental dilemma posed by the mind-brain interaction problem, i.e. how is it that the mind which is subjective and immaterial, can interact with the brain which is objective and material? Analysis of recent experiments appears to indicate that quantum mechanics may have a role to play in the resolution of the mind-brain interaction problem in the form of biological entanglement and nonlocality. In addition to this analysis, when coupled with ongoing and proposed experiments, may help us to simultaneously resolve related issues such as whether mental events can initiate neural events, the transference of conscious subjective experience, the measurement problem and the binding problem.     

Cell assemblies in the cerebral cortex

Donald Hebb’s concept of cell assemblies is a physiology-based idea for a distributed neural representation of behaviorally relevant objects, concepts, or constellations. In the late 70s Valentino Braitenberg started the endeavor to spell out the hypothesis that the cerebral cortex is the structure where cell assemblies are formed, maintained and used, in terms of neuroanatomy (which was his main concern) and also neurophysiology. This endeavor has been carried on over the last 30 years corroborating most of his findings and interpretations. This paper summarizes the present state of cell assembly theory, realized in a network of associative memories, and of the anatomical evidence for its location in the cerebral cortex.     

Cold stress interaction on organophosphate insecticide poisoning: age-related assessment in rat cerebral cortex

The present study was undertaken to identify the nature of the interactive effects of chlorpyrifos (CPF) and cold stress (15 degrees and 20 degrees C) on the activities of acetyl cholinesterase (AChE), choline acetyl transferase (ChAT), Na+, K(+)-ATPase and malondialdehyde (MDA) level in the cerebral cortex of 1 week, 3 weeks and 3 months of age. The results indicated an interaction of CPF with age of animal and cold exposure resulting in marked decrease in the activity levels of AChE, ChAT, Na+, K(+)-ATPase, followed by increased MDA levels. Overall, the effects of co-exposure of cold stress and CPF were appreciably different from either of the exposures. However, synergistic-action of CPF and cold stress at 15 degrees C showed a greater inhibition of AChE, ChAT, and Na+, K(+)-ATPase in comparison with CPF or cold stress alone and together at 20 degrees C. The results reveal that young animals are markedly more sensitive to interactive effects of CPF and cold stress than adults.