Tobacco Documents Online

0111HE COUNCIL FOR TOBACCO RESEARCH-U.S.A., INC. July 26, 1984 ~A-:5--i'V - cIAo.,.o'; 1 MEMO • TO: Dr. S. C. Sonme.rs and Staff FRCM: D.H. Ford and D. Stone RE: Site visit with Dr. A. fajtha, Center for Neurochemistry, Ward's Island, N.Y. on May 30, 1984. Grant No. 1234 BR1 entitled "Nicotine Effects on the metabolism of Specific proteins: developnental and genetic influences." Overview. Dr. Lajtha considers that the CNS has an organizational specificity, but not a specific receptor or ligand (transmi.tter) for each function. Various combinations of the different units confer the specificity. Ie. Endorphin, a five amino acid peptide with apparently more than one type of receptor (enkephalin has 5 different receptor types) is degraded by several different enzymes which degrade it at different sites which appear to have some specificity depending on the location of the receptor %here degradation occurs. This type of variance in degradation pattern appears to provide a degree of specificity in function. Thus, specificity wnuld appear in part to depend on various peptide/agonist/antagonist interactions with the proteases which degrade them. This may be further modified, since these same proteases also alter the receptor proteins...this alteration implies that the response to a transmitter may not be all or none. Further malifications in response may occur because many peptide transmitters are released into the extracellular space rather than at a synapse to influence the neuronal me.mbrane at a non- synaptic site. V~hzat is the effect of nicotine on such a system of peptide synaptic transm.itters and modulators? First, it nust be noted that brain protein is not stable, but dynamic and that many CNS responses involve conplex protein en- zyme systems in non-synaptic as well as synaptic functions. Does nicotine alter specificity of brain proteins (enzyms) at receptor ligand sites of interaction? It well may because nicotine lowers body temperature about . 2.5 to 3°C and each degree drop in tenperature decreases protein synthesis about 6%. Would this bring about a decrease in all protein synthesis or just selective proteins? It may be selective since the heat induced by fever in- creases the synthesis of a "stress protein." This protein may also be induced by cold, injury stress or horcronal stress. Thus, the focus of the current studies will be to determine if the reduced protein synthesis observed in neonates exposed to nicotine is selective. Early results indicate that it may be since the receptor (protein) which binds nicotine is itself increased by Prenatal exposure to nicotine. Sershen; Suinnarization of results accuneilated in first 4 years of grant support: This study used both mice and rats. The mice were Ba1bC and C57B1. One

2 is a high activity strain mouse whose activity in a maze is not improved by nicotine. The other is a low activity muse whose performance was im- proved by nicotine. Results: Nicotine is rapidly taken up by the brain of rat or muse (betterlthan water),but not repidly metabolized. Nicotine uptake is essen- tially passive, as its rapid exit. It has no effect of amino acid uptake in adult brain in intact an.imal or brain slice studies. Nicotine analogues, nicotinamide, proline, ethanol, lysine, GABA do, not inhibit nicotine uptake. Nbrphine, however, decreases nicotine uptake 30-50%. Nicotine uptake by brain is non saturable and it can not be sinply binding to receptors, because it also binds to tubulin. Nicotine increased cerebral blood flow.1-Nicotine stirrgzlates brain protein synthesis in adult muse mother about 38%, but de- creases it in the fetus 19% ... in vitro. In vivo, nicotine had no effect in the adult muse brain, but still decreased protein synthesis in the newborn 20%. In the adult rat (in vivo) nicotine increased protein synthesis about 20% in the cerebral cortex, brain stem and cerebellum. Shioke exposure in several strains of muse had an effect on adult brain protein synthesis. Valine incorporation in BalbC and CBH mice was depressed in brain and liver, even after correcting for the decreased protein synthesis caused by the drop in body temperature. The decrease in protein synthesis after exposure to smoke was shown not to be due to CO, since exposure to CO levels conparable to that in the smoke had no effect. High levels of CO did, however, reduce both brain and liver protein synthesis, which was probably due to anoxia. Further, there was no long term adaptation to smoke, as even in chronic studies, protein synthesis was depressed. This was not due to an effect on amino acid transport, but on incorporation. The effect of smoke exposure in mice on protein synthesis lasts for about 1 hour. 1-Nicotine was also shown to depress brain protein degradation in newborn muse brain slices; thus both synthesis and degradation were depressed in muse neonates. This probably accounts for the observation that neonates exposed to nicotine in utero had normal brain weights. At least one protein is in- creased by prenatal exposure to nicotine: the protein of the nicotine receptor. This may be the ACh receptor as well, since some investigators have shown an increase in ACh binding after prenatal exposure to nicotine. Nicotine blocks the amnestic effects of cyclohexanLide. However, this does not appear to be due to any effect on the inhibition of protein synthesis caused by cyclohexamide. Nicotine binding site studies suggest that they may be either cholinergic or non-chobnerigic or both. There seem to be receptors for both d and 1-nicotine. There also appears to be some relationship to the enkephalin/endorphin ligand receptor system involved in the response to nicotine. Endogenous nicotine-like ligand: A ligand has been isolted which mimics nicotine and whose binding partly blocks the binding of 3H-nicotine. It also blocks ACh binding. Preliminary studies on a relatively pure fraction suggests it may be a small peptide. NMPTP studies: Initial studies with mice show that SC injection over a prolonged period reduces DA uptake in the striatum 63%. No effect was ob- served in a control tissue (olfactory bulb). Uptake of cocaine was also

.3 reduced by 61%. This implies a loss of receptors for both ligands. They may or may not be the same receptors. In fema]..es, NMP`I'P reduced cocaine bind- ing to levels seen in normal old males. A great deal of information relative to the rodent brain protein syn- thesis and nicotine has been acctmulated. Effects on adults seem to be minimal. The drop in body temperature which occurs from nicotine could have long term effects in a dynamic . protein synthesizing organ were it not for the fact that tolerance seems to develop to the drop in body temperature. In neonates, however,the effects on protein synthesis may have long term effects since they occur at a time of differentiation and maturation of many neuronal systems, some of which could influence behaviour in the adult. This study appears to be progressing well and accumulating information relevent to the problem of prenatal exposure to nicotine or smoke. Therefore, it still merits the interest and support of CTR. DHF and DS Note, their HPLC equipment needs upgrading to increase the volume of wnrk which can be performed two to three fold. Lajtha may approach us for a supplettent for this equipment or include it in his next renewal.