Amedeo S. Marrazzi

The Sympathetic Component of the Sciatic Nerve

Our present knowledge of the course of the preganglionic nerve fibers is based largely on the early experiments of Langley 1 , 2 and Bayliss and Bradford 3 who used erection of hairs, sweating and vascular changes for recording sympathetic activity. These types of effector activity do not lend themselves readily to quantitative estimation. Moreover sweating and vasomotor changes offer additional difficulties in that they are complex responses. Sweating is influenced by accompanying vascular changes while vasomotor effects in turn are subject to rapid modification by compensatory reflexes. In the present experiments a direct insight into the kind and magnitude of the sympathetic nerve impulses themselves was obtained by recording the action potentials in the efferent nerves. A direct current amplifier, which Marrazzi 4 had found, in recording action potentials from other parts of the sympathetic system, to be especially suitable, was utilized to actuate a Matthews oscillograph. This technique provides not only a means of tracing the pathway of preganglionic fibers to an organ or a limb but enables the analysis of an exact point-to-point representation of the sympathetic component of each ventral root in any peripheral nerve. Method. In a series of experiments on 19 cats, lightly anesthetized with nembutal or sodium amytal the spinal nerve roots from T7 to L7, inclusive, were severed from the cord, the dorsal root and ganglion excised; and the distal cut end of the ventral root stimulated, after insulation from surrounding tissues, by accurately controlled shocks from a thyratron stimulator. The activity resulting in the sciatic nerve was detected by electrodes placed on the main branches of the ipsilateral nerve and connected to the amplifier. The B and C waves thus recorded enabled us to map the exact roots through which sympathetic fibers passed to the lower limb via the sciatic nerve.

Quantified LSD effects on ego strength.

The ego has been characterized by Smith [1] as “a coherent organization of mental forces which arranges the processes of the mind in relation to time and reality,” and ego strength according to Mora [2] is “an empirical measure of the level of integration.” It is from such emphasis on the organizational and integrative aspects of mental health and the disorganizing effects of hallucinogens such as LSD that our proposal to measure ego strength stems.

Correlation of the Cerebral Biochemical and Functional Effects of Monoamine Oxidase Inhibitor Antidepressants

One group of so-called antidepressants belongs to the monoamine oxidase (MAO) inhibitors. It therefore seemed instructive to examine the correlation between the chemical and functional changes induced in the brain by monoamine oxidase inhibitors and to ask how these are related to an antidepressant action.

Relation of Drug Action to a Cholinergic Mechanism at Sympathetic Synapses

Current pharmacological concepts embrace the possibility that drugs acting at junctions, where acetylcholine plays an important though perhaps not essential rôle in transmission, do so by exerting their influence on some step in the cholinergic mechanism. The consistency of such a view was examined by studying the effects on a sympathetic ganglion of drugs known to act at the parasympathetic neuro-effector junctions, since both are sites where cholinergic systems operate. Pertinent observations may be found in papers by Langley, 1 by Dale and Laidlaw, 2 etc. Action potentials of the tonic impulses normally coursing in the superior cervical preganglionic trunk of the rabbit (anesthetized with nembutal) and of the response in the postganglionic fibers were recorded by a Matthews oscillograph after amplification. The waves were also spread out for visual observation by a rotating mirror (speed corresponding to 1.8 meters per second) and converted into sound by a loud speaker. Pilocarpine, representing the parasympathomimetic stimulants, and atropine, the depressants, were injected into the common carotid artery, all branches except to the ganglion having been ligated and cut and the carotid sinus nerve severed. Thus the ganglionic circulation was retained intact while allowing an effective concentration at the synapse before diffusion into the general circulation. This made possible the observation of local effects uncomplicated by distant actions such as on the central nervous system directly, or indirectly through the remaining innervated carotid sinus responding to vascular changes. The increase in postganglionic impulses (compare records A and B, C and D) illustrates the stimulant effect of small doses of pilocarpine. This increase, seen again in E, F, took place without any change in the corresponding preganglionic records G and H, and consequently must have been due to a truly peripheral action at the synapse.