Neurohumoral substances

The regulation of the total peripheral resistance also involves the complex interactions of several mechanisms. These include baroreflexes and sympathetic nervous system activity response to neurohumoral substances and endothelial factors myogenic adjustments at the cellular level, some mediated by ion channels and events at the cellular membrane and intercellular events mediated by receptors and mechanisms for signal transduction. As examples of some of these mechanisms, there are two major neural reflex arcs (Fig. 1). Baroreflexes are derived from high-pressure barorecep-tors in the aortic arch and carotid sinus and low-pressure cardiopulmonary baroreceptors in ventricles and atria. These receptors respond to stretch (high pressure) or... 

The fact that most serotonergic dorsal raphe neurons are dependent on extrinsic excitatory or facilitatory inputs to express their characteristic spontaneous activity may seem to contradict previous studies suggesting that these neurons may function as autonomous pacemakers (42) with an endogenous rhythm (31) attributable to the presence of pacemaker potentials (8). Such a contradiction exists only if one insists that endogenous rhythms and pacemaker potentials must, by definition, be totally autonomous, i.e., completely independent of all extrinsic synaptic or neurohumoral influences. Such a definition would seem too restrictive in view of the fact that some invertebrate neurons display pacemaker potentials only when certain afferent fibers are stimulated (38) or when exposed to certain neurohumoral substances (18,28). 

PSYCHOTROPIC DRUGS AND NEUROHUMORAL SUBSTANCES IN THE CENTRAL NERVOUS... 

The demonstration that a substance is released on stimulation of a tract of nerve fibres provides useful evidence that it is present in nervous rather than in glial tissue. Its transmitter function becomes more likely if it can be shown that the amount released is sufficient to stimulate or inhibit neighbouring nerve cells. Recent advances in histochemistry have permitted the more accurate localization of neurohumoral substances not only between neurones and glial tissue, but also within the subcellular components of individual cells. 

Acetylcholine occupies a unique position among neurohumoral substances for it is the only one which has been conclusively shown to have a transmitter function at central synapses. The relevant evidence has been extensively... 

POLYPEPTIDE ANTIBIOTICS OF MEDICINAL INTEREST—R. O. Studer NON-STEROIDAL ANTI-INFLAMMATORY DRUGS—S. S. Adams and R. Cobb THE PHARMACOLOGY OF HEPARIN AND HEPARINOIDS—L. B. Jaques THE HISTIDINE DECARBOXYLASES—D. M. Shepherd and D. Mackay PSYCHOTROPIC DRUGS AND NEUROHUMORAL SUBSTANCES IN THE CENTRAL NERVOUS SYSTEM—J. Crossland THE NITROFURANS—K. Miura and H. K. Reckendorf... 

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