The influence of certain chemical substances on the initiation of sensory discharges in pulmonary and gastric stretch receptors and atrial receptors

Veratrum Alkaloids with Antihypertensive Activity

“…Increased activity in afferent fibers from left atrial mechanoreceptors under the influence of Veratrum ester alkaloids was reported by PAINTAL (1955PAINTAL ( , 1957 and NEIL and JOELS (1961); afferent fibers from right atrial receptors require higher doses of the alkaloids (PAINTAL, 1957;NEIL and JOELS, 1961).…”

“…At the cellular level, the Veratrum ester alkaloids cause their stimulating (and simultaneously desensitizing) effect probably by an action upon the regenerative region of the receptqr, rather than the generator region or the nerve fiber central to the regenerative region (PAINTAL, 1957(PAINTAL, , 1964(PAINTAL, , 1971. In medullated nerve fibers, Veratrum ester alkaloids are known to induce a negative afterpotential on which repetitive afterdischarge may be superimposed; at higher concentrations depolarization occurs (see ULBRICHT, 1969).…”

Sensory Mechanisms Involved in the Bezold‐jarisch Effect

“…In one investigation it seemed that the endings (jf the right atrium were not .stinuilated in the same way (Paintal, 1955). On the other hand, Neil and Joels (1961), using larger doses of the alkaloids (veratrine), found that the right-sided endings were also stimulated; such responses had also been reported earlier (Paintal, 1957). Perhaps there is only a small difference between the responses of the endings of the two sides to the alkaloids, a difference that hits been attributed to the high P<-(x of the hlood in tlie right side (Paintul, 1964).…”

“…Here it can be seen that the ending was .stimulated but not sensitized, because the discharge in the sea)nd ending (which was not stimulated) and which provides an index of the intensity of tlie natural stimulus reveals that this had uot increased grossly. Moreover, it can he seen tluit the peak frequency of discharge is not niuch higher than the lowest frecjuency of discharge, a feature which not only shows that the L-nding was not seasitized but that it was probably de'sensitized as well (Paintal, 1957).…”

Activity of Abdominal Muscles Elicited From the Circulatory System

“…It is postulated, therefore, that steady state contractions, and consequently the ACR, become inhibited when the volume of blood within a certain restricted portion of the cardiovascular system is sufficient to activate mechanoreceptors (volume, pressure, or stretch receptors). The receptors described by Whitteridge (98), Paintal (76,80), Neil (74) and Coleridge et al (24) which are activated during filling of the atria apparently would be useful for this purpose; but, a priori, receptors in the walls of the ventricles which are activated by a rise in ventricular volume also would be useful. In addition, receptors in the pulmonary circuit require consideration (3-5, 23, 27, 32, 33, 81, 82).…”