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Blood Cholinergic Parameters as a Potential Index of Central Cholinergic Function
478 Blood Cholinergic Parameters as a Potential Index of Central Cholinergic Function 1. HANIN, U. KOPP, C. NEVAR, D.C.SPIKER, J.F. NEIL and D.J. KUPFER Western Psychiatric Institute and Clinic, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 (U.S.A.)
Experiments have been conducted in our laboratories t o establish whether it is feasible t o utilize red blood cell (RBC) and plasma choline (Ch) as an index of brain cholinergic function in vivo (Shih, T.-M. et al., Neurosci. Abstr. 3, 322, 1977). An animal model has been developed which has provided encouraging results justifying the initiation of parallel studies of RBC and plasma Ch profile in human subjects. Our studies t o date in human subjects indicate that: (1) within an individual, RBC and plasma Ch levels are maintained at an unusually constant level for months, provided external conditions and dietary factors are unchanged; ( 2 ) tremendous interindividual differences, o n the other hand, d o exist in RBC Ch levels, and they have been shown t o span over a 20-fold range (Hanin, I., et al., Cholinergic Mechanisms and Psychopharmacology, D.J. Jenden, Ed., Plenum, New York, pp. 181-195, 1978); (3) these differences among individuals may furthermore be related in some manner t o differences in the behavioral state of these individuals. Unipolar depressed, drug-free patients were shown t o have significantly higher RBC Ch levels ( 5 1.7 f 18.4 nmol/ml; n = 15) than normal controls (10.2 f 1.O nmol/ml; n = 10). Plasma Ch levels, at the same time, were similar in both groups; (4) finally, treatment of depressed patients with the antidepressant, amitriptyline (Elavil@), had no effect o n RBC and plasma Ch levels, implying that endogenous factors play a major role in controlling the levels of RBC and plasma Ch in various individuals. We believe that the higher observed levels of RBC Ch in some of our depressed patients are related in some very specific manner t o the concept of a definitive involvement of cholinergic mechanisms in affective disease states. The nature and extent of this relationship are currently under further investigation in our laboratories, Supported by NIMH grant No. MH 26320.
Ultrastructure of the Cholinergic Synapse Revealed by Quick-Freezing JOHN E. HEUSER and SHELLEY R . SALPETER Department of Physiology, University o f California School o f Medicine, San Francisco, CA (U.S.A.)
This abstract outlines the use of quick-freezing t o elucidate the ultrastructure of the cholinergic synapse and to capture the structural changes that underlie synaptic transmission. The machine developed for this purpose (Heuser, J.E., et al., Cold Spring Harbor Symp. quant. Biol., 40, 17-24, 1976), is designed t o stimulate nerve-muscle preparations, record the resulting end-plate potentials, and at precisely timed intervals thereafter t o freeze the tissues almost instantaneously by plunging them o n t o a pure copper block cooled t o 4'K with liquid helium. High speed resistance and capacitance measurements at the time of impact indicate that the surface of the muscle freezes within one msec. Quick-freezing of the frog neuromuscular junction has been used t o reconstruct the sequence of events that occurs during presynaptic nerve secretion. First, it has established that transmitter release is brought about b y exocytosis of synaptic vesicles, by showing that such exocytosis occurs at exactly the same time as transmitter release, and that one synaptic vesicle opens for each quantum that is discharged (Fig. 1) (Heuser, J.E., et al., J. Cell Biol., in press). Second, quick-freezing has shown that discharged vesicle membrane begins t o be retrieved from the plasma membrane within a few seconds, by a specialized form of endocytosis known as "coated vesicle" formation. These sorts of timing experiments add further evidence in favor of the original idea of Heuser and Reese (J. Cell Biol., 57,315-344, 1973)
Experiments have been conducted in our laboratories t o establish whether it is feasible t o utilize red blood cell (RBC) and plasma choline (Ch) as an index of brain cholinergic function in vivo (Shih, T.-M. et al., Neurosci. Abstr. 3, 322, 1977). An animal model has been developed which has provided encouraging results justifying the initiation of parallel studies of RBC and plasma Ch profile in human subjects. Our studies t o date in human subjects indicate that: (1) within an individual, RBC and plasma Ch levels are maintained at an unusually constant level for months, provided external conditions and dietary factors are unchanged; ( 2 ) tremendous interindividual differences, o n the other hand, d o exist in RBC Ch levels, and they have been shown t o span over a 20-fold range (Hanin, I., et al., Cholinergic Mechanisms and Psychopharmacology, D.J. Jenden, Ed., Plenum, New York, pp. 181-195, 1978); (3) these differences among individuals may furthermore be related in some manner t o differences in the behavioral state of these individuals. Unipolar depressed, drug-free patients were shown t o have significantly higher RBC Ch levels ( 5 1.7 f 18.4 nmol/ml; n = 15) than normal controls (10.2 f 1.O nmol/ml; n = 10). Plasma Ch levels, at the same time, were similar in both groups; (4) finally, treatment of depressed patients with the antidepressant, amitriptyline (Elavil@), had no effect o n RBC and plasma Ch levels, implying that endogenous factors play a major role in controlling the levels of RBC and plasma Ch in various individuals. We believe that the higher observed levels of RBC Ch in some of our depressed patients are related in some very specific manner t o the concept of a definitive involvement of cholinergic mechanisms in affective disease states. The nature and extent of this relationship are currently under further investigation in our laboratories, Supported by NIMH grant No. MH 26320.
Ultrastructure of the Cholinergic Synapse Revealed by Quick-Freezing JOHN E. HEUSER and SHELLEY R . SALPETER Department of Physiology, University o f California School o f Medicine, San Francisco, CA (U.S.A.)
This abstract outlines the use of quick-freezing t o elucidate the ultrastructure of the cholinergic synapse and to capture the structural changes that underlie synaptic transmission. The machine developed for this purpose (Heuser, J.E., et al., Cold Spring Harbor Symp. quant. Biol., 40, 17-24, 1976), is designed t o stimulate nerve-muscle preparations, record the resulting end-plate potentials, and at precisely timed intervals thereafter t o freeze the tissues almost instantaneously by plunging them o n t o a pure copper block cooled t o 4'K with liquid helium. High speed resistance and capacitance measurements at the time of impact indicate that the surface of the muscle freezes within one msec. Quick-freezing of the frog neuromuscular junction has been used t o reconstruct the sequence of events that occurs during presynaptic nerve secretion. First, it has established that transmitter release is brought about b y exocytosis of synaptic vesicles, by showing that such exocytosis occurs at exactly the same time as transmitter release, and that one synaptic vesicle opens for each quantum that is discharged (Fig. 1) (Heuser, J.E., et al., J. Cell Biol., in press). Second, quick-freezing has shown that discharged vesicle membrane begins t o be retrieved from the plasma membrane within a few seconds, by a specialized form of endocytosis known as "coated vesicle" formation. These sorts of timing experiments add further evidence in favor of the original idea of Heuser and Reese (J. Cell Biol., 57,315-344, 1973)