PREPARATION OF A NERVE-STIMULATING PHOSPHOPEPTIDE (SUBSTANCE B, NERVESIDE) IN BRAIN EXTRACTS AND AN ENZYME IN BRAIN WHICH INACTIVATES IT

The action of nerveside, a peptide extracted from brain, on myenteric ganglia in Auerbach's plexus

1. In the rabbit jejunum nerveside causes alternating contractions of the longitudinal and circular muscles, which are similar to the peristaltic reflex produced by distension of the gut. These effects are abolished by dibucaine (Nupercaine) and tetrodotoxin. The site of action is located in Auerbach's plexus.2. Circular muscle contractions due to nerveside are blocked by hexamethonium, nicotine, morphine, atropine and hyoscine. There is no circular response to nerveside after removal of Auerbach's plexus. It is suggested that nerveside acts by stimulating presynaptic nerve terminals which are cholinergic and that the circular muscle is innervated by cholinergic nerve fibres.3. Longitudinal muscle contractions due to nerveside are not affected by hexamethonium but can be blocked by paralysis of myenteric ganglia with nicotine. They are not abolished by morphine or by cholinolytic drugs. It is suggested that nerveside acts by stimulating either receptors insensitive to acetylcholine in ganglion cells or non-cholinergic presynaptic nerve terminals. It is further suggested that the longitudinal muscle of the rabbit gut is supplied by non-cholinergic as well as cholinergic nerve fibres.

The inhibitory effect of convulsant agents on the enzyme in brain which inactivates nerveside

1. An enzyme which can be extracted from brain inactivates nerveside in the optimum pH range 5.8-7.0.2. The polybasic acids trypan blue and its analogue trypan red, bromphenol blue and its analogue bromthymol blue at concentrations of 0.22 mM and ethylenediaminetetra-acetic acid (EDTA) at a concentration of 1 mM are strong inhibitors of the enzyme.3. Penicillin which is a monobasic carboxylic acid also inhibits the enzyme but only if concentrations as high as 3.6 mM are used. The antibiotic streptomycin which is a basic substance does not inhibit the enzyme.4. Caffeine at a concentration of 7.2 mM only weakly inhibits the enzyme.5. Chymotrypsin and wheat germ acid phosphatase also inactivate nerveside at pH 5.9 and are inhibited by the acidic dyes and penicillin. EDTA inhibits wheat germ phosphatase but activates chymotrypsin.6. Inactivation of nerveside by the brain enzyme and by wheat germ phosphatase is different from the action of chymotrypsin. Nerveside solutions incubated with chymotrypsin completely lose all biological activity whereas if incubation is carried out with either the brain enzyme or wheat germ acid phosphatase a residual biological activity remains even when the concentration of these two enzymes is increased. This residual biological activity is due to a peptide as it is destroyed by chymotrypsin.7. The manner in which nerveside is inactivated by the brain enzyme is uncertain as the preparation of the latter contained phosphodiesterase and protease activities which were similarly inhibited by the acid dyes, penicillin and EDTA.8. Pentylenetetrazole, picrotoxin, strychnine and tetanus toxin do not inhibit the brain enzyme.9. The nerveside-inactivating enzyme is not identical with the Substance P-inactivating enzyme in brain as the former is inhibited by EDTA while the latter is not.

The regional distribution of the nerve-stimulating phosphopeptide (nerveside, substance B) in the central nervous system

1. The nerve-stimulating phosphopeptide, nerveside, is present mainly in the cerebrum and brain stem, while the cerebellum contains only a trace amount of it.2. Nerveside is uniformly distributed over all parts of the cerebral cortex.3. The cerebral cortex contains the greatest concentration of nerveside. If the nerveside activity of 1 g cerebral cortex is expressed as 100 then the relative activities of the other parts of the C.N.S. are hippocampus 41, caudate nucleus 21, diencephalon (without hypothalamus) 24, midbrain 19, pons 7, medulla 12 and cerebellum 6.4. The nerveside activity of the hypothalamus is the same as that of the cerebral cortex.5. The pattern of distribution of nerveside in the C.N.S. suggests that it may be part of a corticipetal or corticifugal system.