1987 — 1989 |
Rosecrans, John A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Effects of Nicotine On Behavior--Site/Mechanism &Action @ Virginia Commonwealth University
The major objective of this research will be to determine brain area sites an cholinergic mechanisms important to nicotine's effects on behavior. Previous research conducted in this laboratory has indicated that neurons in the hippocampus (Hp) and midbrain reticular formation (MRF) are somehow involved in the ability nicotine (400 microgram/kg, s.c.) to exert discriminative stimulus (DS) control of behavior. In addition the nicotine- induced DS appeared to have a non-cholinergic component as we were unable to mimic the nicotine DS by increasing brain acetylcholine (ACh) levels via the administration of phsostigmine (250 microgram/kg, s.c.) muscarinic receptors were blocked by atropine. The major direction of the research to be conducted will further define the nature of the nicotine-induce DS. Thus, we will initially study the role of the HP and MRF further using different nicotine training doses (100 and 200 microgram/kg) and will study the generalization of the peripherally-induced DS to each brain site by perfusing a given site with nicotine and other cholinergic agonists using an EMIT perfusion apparatus. This central perfusion approach will be used to evaluate other brain area sites in relation to the peripherally-mediated nicotine DS and will also be utilized to study the effects of nicotinic and muscarinic stimulation on other operant behaviors as well. Thus, in addition to studying the importance of a given brain area site to the DS properties of nicotine we will also attempt to characterize each brain area site as it relates to the effects of nicotinic/muscarinic stimulation and/or inhibition on simple operant behaviors. Such an approach will provide information important to both nicotine's effects on behavior and the importance of specific cholinergic neurons (muscarinic and nicotinic) to behavior. A major goal of this research will be to identify nicotinic sites sensitive to ACh using in vivo behavioral approaches. To date few investigators have demonstrated that ACh-elicited effects can be antagonized by nicotinic receptor antagonist such as mecamylamine; most direct or indirect-elicited ACh effects are antagonized the muscarinic antagonists atropine. This aspect of the research will be studied using the perfusion of brain area sites with ACh analogs such as methacholine with the goal of demonstrating that a given behavioral effect can be selectively antagonized by muscarinic and/or nicotinic antagonists.
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0.958 |
1993 |
Rosecrans, John A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neuroimmune Mechanisms of Morphine Immunosuppression @ Virginia Commonwealth University
The work outlined in this application lies at the intersection of two of our society's pressing problems, drug abuse and the AIDS pandemic. While the incidence of new AIDS cases has been declining among some of the traditional high risk groups the problem among intravenous drug users is worsening. There is evidence to indicate that opiates have the potential to suppress the immune system and, unfortunately, this fact may create a situation in which i.v. drug abusers are placing themselves in a biological, type of "double jeopardy." While the literature contains a number of reports which suggest that opiates are able to affect the functioning of the immune system, the mechanism by which morphine addiction alters the immune response is not clear. However, it seems that an opiate such as morphine may have a direct effect on the immune system or, alternatively, an indirect one. The indirect mechanism may involve altered levels of neuroendocrine hormones. There is evidence which suggests that opiates are able to affect the immune system through both direct and indirect mechanisms. The hypothesis which we plan to test is; "The profound immunosuppression observed following morphine administration to mice is not attributable to a single mechanism. Morphine's direct effects on immunologic cells are compounded by other immunosuppressive events which relate to morphine's actions in the brain. These indirectly immunosuppressive actions of morphine involve the hypothalamic-pituitary-adrenal (HPA) axis as well as the sympathetic nervous system (SNS)." To evaluate the validity of this hypothesis, the following specific aims are proposed: (1) Define the parameters of the thymic atrophy and humoral immune suppression observed in mice implanted with a morphine pellet. (2) Deter-mine the mechanisms which account for the marked in vivo thymic atrophy observed in mice treated with morphine. (3) Determine the mechanisms by which morphine causes in vivo suppression of the splenic humoral immune response to an injection of SRBC. To accomplish these aims a combination of in vitro and in vivo studies are planned. Experiments have been designed to better define the immune deficits which occur in morphine treated mice and to determine which cells of the immune system are most susceptible. The morphine susceptibility of primary relative to secondary immune responses will be examined. Flow cytometry will be used to identify the subpopulations of cells which are depleted from the spleen and thymus following morphine treatment. Studies to identify apoptosis as the mechanism by which morphine induces thymic atrophy are planned, as well experiments to assess the role of the HPA axis and SNS in initiating it. Experiments will be performed to determine the relative contribution of morphine's direct vs. it's indirect effects in the suppression of the antibody response in the spleen. Separation-reconstitution studies will identify the cell, or cells, in the antibody response which are functioning subnormally. Completion of the proposed experiments should contribute to an understanding of the direct and neuroimmune mechanisms through which morphine is able to suppress immunity.
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0.958 |
1994 — 1995 |
Rosecrans, John A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Cocaine and Immunocompetence--Role of Metabolism @ Virginia Commonwealth University
We initially determined that direct addition of cocaine to splenocytes from female B6C3F1 mice only produced nonsignificant suppression of the in vitro T-dependent antibody (Ab) response to SRBC, and only at the highest concentrations tested (21% and 41% at 10-5M and 10-4M, respectively). These results are not consistent with a direct immunomodulation by cocaine, because these concentrations are much greater than reasonable blood levels in cocaine users. The purpose of this study was to examine possible indirect effects of cocaine on the immune system, with an emphasis on a role by reactive metabolites. Cocaine is metabolized to norcocaine and, ultimately to more reactive intermediates, via a minor metabolic pathway mediated by the cytochrome P-450 system. The generation of these metabolites is associated with hepatotoxicity, which is both sex- and strain-dependent, and which can be increased following the administration of a P-450 inducer like phenobarbital (Pb). Subchronic (14 day) exposure in female B6C3F1 mice produced a significant decrease in the Ab response to SRBC only at the highest dose tested (80 mg/kg); lower doses were without effect, even though mice were obviously affected (i.e., female B6 mice were hyperactive when exposed to cocaine at 40 and 60 mg/kg/day). In contrast, a significant decrease of 50% was observed in female DBA/2 mice exposed to 60 mg/kg/day in male B6C3F1 mice exposed to 40 mg/kg/day. Pretreatment with Pb markedly increased the suppression in female B6C3F1 mice, with 30 mg/kg producing a decrease of ~30% and 60 mg/kg producing a significant decrease of >70%. Additional evidence has been derived from in vitro studies using the Ab response to SRBC by splenocytes from female B6 mice: (1) direct addition of norcocaine was 10-fold more suppressive than cocaine (decreases of 21% and 53% were noted at 10-6 M and 10-5 M, respectively); and (2) concentrations of cocaine, which were inactive when added to splenocytes alone, suppressed the Ab response when preincubated with an S-9 liver homogenate from Pb-induced female B6 mice, or when added to a co-culture system (primary hepatocyte-splenocyte from female B6 mice), which was developed and optimized by this laboratory to study the immunological effects of reactive intermediates. These preliminary results suggest that cocaine immunomodulation may be mediated, at least in part, through the generation of P-450-dependent reactive metabolites. The primary objective of this investigation will be to confirm a role by metabolism in cocaine's effects on immunocompetence. The studies will include a determination of a possible mechanism of action at a biochemical level - i.e., depletion of glutathione. A secondary objective will be to characterize the profile of activity of cocaine using optimal conditions for immunosuppression (i.e., as established with the Ab response to SRBC) and a number of parameters reflecting several aspects of immune function. These studies will provide some indication of the mechanism of cocaine's action at the cellular level by describing if it selectively affects a given cell type or functional endpoint.
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0.958 |