background

2004-2005

 

Electroacupuncture failed to affect the development of locomotor sensitization to nicotine and cocaine and cross sensitization to amphetamine

Naira Arellano (Neuroscience)

Advisor: John Kelsey

It has been reported that acupuncture in humans and animals can be useful in treating several aspects of addiction, including withdrawal, reward, and sensitization. In this study, I examined the effects of electroacupuncture (EA) at the Zusalini point (ST36) in rats on the development and expression of locomotor sensitization to repeated injections of nicotine and cocaine and the expression of cross sensitization to amphetamine. In the present investigation, rats received injections of 0.4 mg/kg s.c. nicotine (Experiment 1) and i.p. injections of 7.5 mg/kg cocaine (Experiment 2) followed by 20 min of 10 Hz EA under anesthesia for 3 days. They then received 3 more days of drug injections alone inlocomotor chambers followed by 3 days of EA alone under anesthesia. One day after the last EA, animals were challenged with 0.4 mg/kg of nicotine in Experiment 1 and 0.5 mg/kg and 7.5 mg/kg of cocaine in Experiment 2. In both experiments animals were also subsequently challenged with 0.5 mg/kg of amphetamine. Electroacupuncture failed to reduce the development or expression of locomotor sensitization to either nicotine or amphetamine. In Experiment 1, EA tended to reduce cross-sensitization to amphetamine, but this trend was not seen in Experiment 2. Although there are many possible reasons for the failure of EA to affect sensitization, it was noted that in the previously successful studies, acupuncture was given immediately prior to testing. I suspect that by giving my last EA before testing, any effect of EA 24 hr may have disappeared by the time of testing.

Extended photoperiod attenuates depressive behavior in fawn-hooded rats

Kelly Baehre (Neuroscience)

Advisor: Roxanne Prichard

Objectives: Despite a considerable amount of evidence for the use of light therapy in the treatment of both SAD and nonseasonal depression, the underlying mechanisms of light therapy are poorly understood.  We utilized the forced swim test (FST) in order to study the behavioral consequences of extended photoperiod in Fawn-Hooded (FH) rats and to determine whether the effects of prolonged photoperiod parallel those obtained with antidepressant drugs, thus providing an animal model in which the mechanism of light therapy can be explored further.   Methods: In order to confirm the FH rat’s depressive state, we first compared their behavior in the FST with compared to Long Evans rats (LE) (n= 12).  The antidepressant desipramine was then given to a subset of the FH and LE rats and behavior in the FST was measured.  The performance of FH rats in the FST was next analyzed after exposure to an extended (16:8h light:dark) and a shortened photoperiod (8:16h light:dark).  Results: FH rats demonstrated greater depressive behavior as compared to LE rats prior to treatment (p < 0.05).  Desipramine reduced depressive behavior in the FH rats (p < 0.05).  Similarly, exposure to an extended photoperiod (16:8 light:dark) decreased depressive behavior in the FH rats as compared to behavior of the FH rats prior to treatment (p < 0.05).  After exposure to a shortened photoperiod (8:16 light:dark) the FH rats showed a significant increase in depressive behavior as compared to behavior following exposure to an extended photoperiod (p < 0.01).  Conclusions:  Extended photoperiod was as effective as pharmaceutical treatment in decreasing depressive behavior of FH rats in the FST.  Due to FH rats’ abnormalities in central serotonin and NPY levels, these neurotransmitters may be involved in the mechanism of light therapy in the treatment of depression.

Molecular characterization of two ionotropic glutamate receptor subunits from the pond snail, Helisoma trivolvus

Kristin Gerhold (Biochemistry- Honors)

Advisor: Nancy Kleckner

Ionotropic glutamate receptors (iGluRs) are a class of four subunit transmembrane proteins which, in the presence of glutamate, form specific pores in the cellular membrane allowing cations, most prevalently sodium, to flow into the cell. In the mammalian nervous system, these channels are important for excitatory signaling between neurons; however, less is known about iGluR function in invertebrates. In the pond snailsHelisoma trivolvis and Lymnaea stagnalis, excitatory glutamate signaling between neurons of the buccal ganglia is essential for the patterning of feeding behavior.  Two iGluR subunits have already been sequenced from Lymnaea and have been shown to be localized in the buccal ganglia, suggesting that they are important in the excitatory signaling that occurs in active feeding behavior. Using a combination of degenerate primer PCR, non-degenerate primer PCR and RACE PCR, I have partially sequenced two non-NMDA iGluRs from the pond snail Helisoma, one of which closely resembles an AMPA-like Lymnaean receptor, Lym-eGluR1, while the other resembles the AplysiaGluR7 receptor. Once full sequence clones of these subunits can be obtained, I will be able to characterize the activity of these Helisoma iGluRs in vitro and provide information which should lead to a better understanding of the molecular mechanisms controlling feeding behavior in these animals.

Performance on a cognitive task as modulated by time of day, sleep debt and alcohol

Caitlin Rose Hager (Neuroscience)

Advisor: Roxanne Prichard

College students are notorious for poor sleeping habits and excessive alcohol consumption. Few studies have investigated the cognitive impairments that may result from sleep loss and alcohol consumption at different times during the day. The present study investigates the interactions between alcohol use and sleep debt on cognitive performance during the morning, afternoon, and evening. In order to assess the effects of alcohol and sleep loss, alcohol consumption was measured by self report and sleep was measured using an actigraph (a device which monitors movement) for about five days. Cognitive performance was measured with a computerized negative priming task. For each participant, cognitive performance was compared at three times of day; within subject analysis was conducted to compare performance following a day of sobriety and a day following a typical night of drinking. The results of this study show that across all groups, cognition is most impaired in the morning, but improves throughout the day (p<0.0l). Furthermore, good sleepers make significantly less errors (p<0.05) and have a significantly faster reaction time (p<0.0l) than bad sleepers. There was a marginally significant interaction between alcohol and negative priming (p=0.11). These results indicate that habits commonly seen in college students are impairing their ability to function at their highest cognitive levels at certain times of day.

The atypical antipsychotic clozapine does not decrease PCP-induced working memory deficits in an animal model of schizophrenia

Robin W. Karfunkel (Neuroscience)

Advisor: John Kelsey

Recent research suggests that working memory (WM) impairment is the core deficit of schizophrenia, and the atypical antipsychotic clozapine has been found to decrease cognitive impairments in schizophrenics. The intent of this study was to investigate whether the psychomimetic phencyclidine (PCP) would decrease accuracy in a spatial delayed non-match to sample (DNMTS) working memory task, and whether this effect can be attenuated with clozapine. As predicted, PCP (4.0 and 5.0 mg/kg) decreased working memory performance in a delay-dependant fashion, i.e., the longer the retention interval between the sample and choice, the larger the impairment produced by PCP. Clozapine was not found to impair working memory at a dose of 3.75 mg/kg, but was found to impair accuracy in a non-delay dependent fashion at 2.0 mg/kg. Moreover, clozapine at these doses did not decrease the detrimental effects of PCP on working memory. In fact, 2.0 mg/kg clozapine made the delay-dependent effects of 5.0 mg/kg PCP non-delay dependent. Further research should be done to further investigate the effects of lower doses of clozapine alone, and in combination with PCP.

Mapping of glutamatergic and glutamate5/6/7 immunoreactive neurons in the central nervous system of the pond snail, Helisoma trivolvis

Angela Knox (Neuroscience)

Advisor: Nancy Kleckner

Glutamate has been shown to have both excitatory and inhibitory effects in controlling such behaviors as feeding in a freshwater pond snail, Helisoma trivolvis (Brierley et al., 1997; Quinlan et al., 1995). To determine the neuronal mechanism by which the feeding behavior is produced, the present study used immunocytochemical techniques with glutamate and vertebrate glutamate5/6/7 receptor (GluR5/6/7) antibodies, and Lucifer yellow dye to determine the physiology of the GluRs in the CNS of Helisoma. Glutamate (Glu-IR)(n = 4) and glutamate receptor 5/6/7 immunoreactivity (GluR5/6/7-IR) (n = 1) was detected on the dorsal surface of the buccal, left and right cerebral, visceral, and left parietal ganglia of the isolated Helisoma central nervous system. Glu-IR was detected bilaterally in interneuron B2, in 1-2 unidentified pairs, and in a neuron with the positioning and morphology of motor neuron B19, on the dorsal side of the buccal ganglia. Ionophoretic injections of Lucifer yellow along with Glu-IR, verified the morphology of interneuron B2, confirming that B2 is glutamatergic. Ionophoretic injections of Lucifer yellow verified the morphology of motor neuron B19 and Glu-IR in neuron B19 provided new evidence for a role of glutamate at the snail neuromuscular junction. GluR5/6/7-IR was detected bilaterally in most buccal neurons, including, neurons B5, B19, and B27 on the dorsal side of the buccal ganglia. These data suggested that glutamate released from B2 may be acting at either a GluR5, 6, or 7 (KA) receptor-like subunit.  Due to the widespread distribution of GluR5/6/7-IR, additional experiments are necessary to determine specificity.

Working memory impairment in a rat model of schizophrenia

Olga Osadchaya  (Neuroscience)

Advisor: John Kelsey

Working memory (WM) impairment has recently been suggested to be the core deficit of schizophrenia (SZ). This higher-order cognitive dysfunction is thought to be associated with deficient transmission of dopamine (DA) in the prefrontal cortex (PFC). The intent of this study was to further examine this hypothesis by determining if direct damage to DA terminals in the rat medial PFC by local injections of DA neurotoxin 6-hydroxydopamine (6-OHDA) can produce cognitive symptoms observed in SZ patients as measured by the delayed non-match to sample test (DNMTS) of WM. Indeed, bilateral 6-OHDA (n = 5) or sham (n = 3) lesions made at four or six different injection sites in the mPFC produced an impairment in choice accuracy that increased as the retention interval (RI) increased. PCP (4.0 and 4.5 mg/kg) further impaired WM, especially in the lesioned animals. Administered alone, clozapine (2.0 and 3.75 mg/kg) tended to impair accuracy only in sham-operated animals at all RIs. In addition, clozapine was unable to attenuate PCP’s memorial effect, but such interaction needs to be tested further at lower doses of clozapine as the drug appears to have a tranquilizing effect on the animals. This study provides further evidence for the hypothesis attributing cognitive symptoms, and especially working memory deficits, to prefrontal hypodopaminergia, and, thus, at the doses used, these data suggest that 6-OHDA-induced hypodopaminergia in mPFC may serve as a rat model of the working memory deficits associated with schizophrenia.

Glutamate signal transduction pathways causing inhibition in buccal B5 and B19 neurons of Helisoma trivolvis

Jason Rafferty (Neuroscience- Honors)

Advisor: Nancy Kleckner

Glutamate has been shown to be an important neurotransmitter in both vertebrate and invertebrate nervous systems.  In the buccal ganglia of the pond snail, Helisoma trivolvus, glutamate transmission allows for a specific pattern of motor neuron activation responsible for feeding behavior.   Glutamate excites motor neurons of feeding phase 2 (S2), and is believed to inhibits neurons of phase 1 (S1) and phase 3 (S3).   However, the receptors and intracellular signaling pathways involved in glutamate-induced responses, particularly in inhibitory signaling, in not well understood.  This project was aimed at determining whether an S1 neuron, B5, and an S3 neuron, B19, are directly inhibited by glutamate and whether the signaling pathways can be classified as ionotropic or metabotropic.  Previous research shows that B5 and B19 are inhibited by glutamate in whole buccal ganglia preparations.  It has been found that S1 and S3 inhibition is not mediated through activation of a glutamate-gated chloride channel or through a G protein activated lipoxygenase pathway.  I hypothesize that glutamate causes this effect through intrinsic pathways rather than through coupling with other neurons, and that glutamate causes inhibition through activation of a G protein inwardly rectifying potassium (GIRK) channel.  To test this hypothesis, B5 and B19 were isolated from intact Helisoma buccal ganglia preparations and grown in culture overnight before standard intracellular recording techniques were used to evaluate glutamate responses.  Glutamate application (100 µM) was sufficient to produce hyperpolarization, the magnitude of which increased at more negative resting potentials.  Glutamate-induced hyperpolarizations were blocked in the presence of 100 µM BaCl2 and CsCl, both known inhibitors of inwardly rectifying potassium (Kir) channels.  B5 and B19 neurons incubated overnight in 1µg/ml pertussis toxin (PTX), an inhibitor of Gi/o proteins, not only prevented glutamate-induced hyperpolarization, but actually allows for glutamate-induced depolarized.   In B19, glutamate-induced hyperpolarizations were enhanced in the presence of 30 nM tertiapin (TERT), an antagonist of GIRK1/4 channels, whereas TERT tended to block glutamate hyperpolarizations in B5.  These results suggest that glutamate acts directly on B5 and B19 to activate both a Gi/o protein and a Kir channel, possibly a GIRK subtype.  Further research is needed to determine the involvement of additional second messenger pathways known to be present in both B5 and B19.

Nicotine does not ameliorate the working memory deficit in the PCP animal model of schizophrenia.

Karina A. Reynolds  (Neuroscience)

Advisor: John Kelsey

Schizophrenia is a debilitating, lifelong disorder which is characterized by positive, negative, and cognitive symptoms. Recent research has indicated that the working memory cognitive deficit of schizophrenia is the core feature of the disorder. As such, utilizing known animal models of schizophrenia to investigate drugs that may treat this aspect of the disorder may prove quite beneficial. Interestingly, one such drug may be nicotine. Given that phencyclidine (PCP) produces many of the symptoms of schizophrenia in humans, I first showed that 4.0 to 5.0 mg/kg PCP would produce a decrease in accuracy in a spatial delayed matching to sample task that tended to worsen as the retention interval between the sample and choice increased. As this PCP-induced deficit could not be attributed to impairments in reference memory, attention, or motivation, it appears as though this deficit reflects a decrease in working memory. Nicotine (0.4, 0.6, and 0.8 mg/kg) had no effect on working memory by itself and failed to ameliorate the working memory impairment caused by PCP. Thus, these results indicate that acute injections of nicotine may not be therapeutic in treating the working memory deficit of schizophrenia.

The effects of common campus drugs on college students’ sleep quality

Cynthia Roman (Psychology)

Advisor: Roxanne Prichard

Psychosocial, environmental, and physiological factors largely contribute to poor sleep quality in college students. The present study focuses on physiological effects of drugs on sleep quality, specifically how common campus drugs such as caffeine, nicotine, alcohol, and marijuana influence sleep quality. Participants include 74 male and 149 female students enrolled at Bates College. Participants completed adaptations of the Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality and an adaptation of the Morningness Eveningness Scale (MES) to assess morning/evening types. Drug intake of each of the 4 drugs was measured by a psychoactive drug survey created for the study, which differentiated between behavior during the week and weekend. Results indicate that poor sleep quality is associated with cigarette smoking, marijuana smoking, ‘binge-like’ drinking, and high caffeine intake. Evening types tend to have lower GPAs, are more likely to drink, engage in binge drinking during the weekend, smoke marijuana, and smoke cigarettes. Cigarette smokers had higher daily caffeine averages, and smokers who consumed alcohol were more likely to smoke more. Average daily caffeine intake significantly predicted levels of sleep quality; higher levels predict poorer sleep quality. Students’ use of each drug was significantly higher during the weekend. Students’ bedtimes were later during the weekend, students got more hours of sleep on the weekend, and they were also able to fall asleep faster on weekend nights. Overall, weekend behavior and sleep quality significantly differed from behavior during the week. Students’ sleep quality was associated with many variables present in the students’ environment, including GPA, alcohol use, caffeine use, and smoking.

Possible involvement of medial prefrontal cortex dopamine in nicotine-induced locomotor sensitization in rats

Whitney Sheen  (Neuroscience)

Advisor: John Kelsey

The mesocorticolimbic dopamine (DA) system, consisting of dopaminergic projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), is one of the primary neural substrates responsible for the mediation of reward in the brain, and the focus of a large body of drug addiction research. Recent studies with cocaine and amphetamine have looked particularly at the role of the mPFC in the mediation of drug-induced reward and sensitization, and have found that depletion of mPFC DA by injections of 6-OHDA enhance a variety of addiction-related behaviors, including locomotor sensitization to acute injections of cocaine and repeated injections of amphetamine. However, other studies have produced evidence contradicting these findings. In an attempt to further elucidate the role of DA in the mPFC, I examined the development and expression of locomotor sensitization to repeated injections of 0.4 mg/kg nicotine and cross-sensitization to challenge injections of cocaine and amphetamine in rats with 6-OHDA mPFC lesions. mPFC lesions only slightly enhanced the development of locomotor sensitization in response to repeated injections of nicotine. Furthermore, there was no significant lesion effect in response to any of the challenges, although, there was a tendency for previously sensitized rats with mPFC lesions to locomote more than previously sensitized sham-operated animals in response to a lower dose nicotine and amphetamine challenge. On the assumption that my lesions sufficiently depleted DA in the mPFC, these findings suggest that mPFC DA is only weakly involved in the mediation of nicotine-induced locomotor sensitization and reward.

Sex differences in stress response to performance and social stress and the negative impact of elevated cortisol on declarative and working memory

Brittny Somley (Psychology)

Advisor: Cheryl McCormick

Different types of stressors appear to differentially impact cortisol elevations in men and women, such that men are more sensitive to performance stressors and females are more sensitive to social stressors. In turn, acute cortisol fluctuations can impact different brain areas responsible for memory by binding to glucocorticoid receptors. This study examined both the impact of a performance (PASAT) and social stressor (Cyberball) on men and women’s salivary cortisol levels and the effect of varying cortisol levels on declarative and working memory, which are respectively dependent on the hippocampus and the prefrontal cortex. Memory tests were taken pre and post stressor and multiple saliva samples were collected to monitor cortisol. Cortisol elevations in response to the stressors were not as profound as expected, but Cyberball appears to be a promising social stressor for laboratory research. As hypothesized, females exhibited significantly elevated cortisol levels fifteen minutes post-stressor as compared to males in the social stress group.  Furthermore, cortisol elevations were more profound in participants who reported that they “believed” Cyberball. A matched group analysis, matched on baseline cortisol samples of those participants who “believed” Cyberball, indicated a marginally significant interaction of group by gender. Consistent with the hypothesis, men exhibited greater cortisol levels than females in the performance stress group and females exhibit greater cortisol levels than males in the social stress group, 15 minutes post-stressor. Significant differences in primacy and recency performance post-stressor were observed such that females had a greater primacy and recency effects in the performance group as compared to the males. A trend was also observed in the social stress group, where males had greater primacy and recency effects than females, post-stressor. Thus, elevated levels of cortisol appear to negatively impact both declarative and working memory, suggesting that glucocorticoid receptors are present in both the hippocampus and prefrontal cortex, respectively.

Molecular and behavioral ontogeny of the masking response in neonatal rats

Carrie Trevisan (Neuroscience)

Advisor: Roxanne Prichard

Objectives: In addition to entraining the circadian rhythm, light also has an immediate effect on sleep/wakefulness. For example, in nocturnal animals, an acute light pulse during the dark phase abruptly decreases locomotor activity.  This behavioral masking response is accompanied by c-fos expression in five nuclei of the retinorecipeint subcortical visual system.  The suprachiasmatic nucleus (SCN), which entrains the 24-hour sleep/wakefulness rhythm, is not required for this response.  In contrast to the development of the circadian system, very little is known about the ontogeny of the subcortical visual system that mediates acute behavioral responses to light. Methods:  In order to examine the molecular and behavioral maturation of the subcortical visual system, we screened neonatal Charles River F344 rats at postnatal days 0 (p0), p6, p12, p17, and p23 for changes in locomotor activity and c-fos protein expression before and after a 30 minute light pulse presented during the subjective night.  In order to examine the effects of inhibitory networks on these responses, the onset of parvalbumin expression in the subcortical visual system was also assessed. Results: Molecular and behavioral masking responses to acute light were first evident at p6, one week prior to eye opening.  In response to an acute light stimulus, locomotor activity significantly decreased (p < 0.01) and c-fos expression in the subcortical visual system significantly increased (p < .05) at p6. At all age groups tested, the magnitude of the behavioral masking response was directly proportional to the extent of light-induced c-fos staining in the subcortical visual system.  Robust c-fos immunoreactivity was first observed in the intergeniculate leaflet (IGL) and ventral lateral geniculate nucleus (vLGN) on p6 (p < 0.05), and by p12,c-fos immunoreactivity was also evident in select nuclei of the pretectum (p < 0.05).  Conclusions:  Acute responses to light are first evident on p6 and continue to maturate through p23.  During this postnatal period, inhibitory networks between the pretectum, geniculate complex and hypothalamic area are undergoing significant refinement.  Masking behavior arises from a delicate balance between these regions, and may be sensitive to environmental factors during this period of development.  The early onset of these acute responses to light show that it is pertinent to understand the consequences of early common light manipulations (e.g., 24-hour lights in hospital nurseries) on the neural circuits that underlie sleep/wakefulness behavior.

An Animal Model of a Neurobiological Link Between Schizophrenia and Drug Abuse

Olivia Zurek (Neuroscience)

Advisor: John Kelsey

Schizophrenic individuals are much more likely to abuse drugs than healthy people or those suffering from other mental illnesses. Although some investigators have suggested that the drug abuse may represent attempts to self-medicate, more recent research has lead to the primary addiction hypothesis, which suggests that the neurobiology underlying schizophrenia and drug addiction are similar such that schizophrenia directly increases the likelihood of drug addiction.  In Experiment 1, the bidirectionality of this hypothesis was examined by determining if medial septal lesions in rats, which have been shown to enhance aspects of addiction, would enhance schizophrenic-like behavior in a hole-board apparatus (HBA).  As previously shown, phencyclidine (PCP; 2-4 mg/kg) increased and raclopride (0.05-0.2 mg/kg) decreased locomotion in the HBA, and medial septal lesioned rats initially increased activity and increased the locomotor response to 4 mg/kg PCP, which is indicative of a slight positive symptomology.  Although PCP decreased head dipping into the holes, the lesions had no effect on this presumably negative symptom.  Experiment 2 showed that 6-hydroxydopamine lesions of the medial prefrontal cortex (mPFC), which also have been shown to enhance aspects of addiction, increased locomotion and the locomotor-enhancing effects of PCP and the locomotor- decreasing effects of clozapine, indicating positive schizophrenic symptomology, while having no effect on head dipping.  Thus, both experiments indicated that lesions that enhance addictive behavior tend to enhance behavior related to the positive symptoms of schizophrenia without affecting negative symptoms.  These results, thus, provide evidence for the overlap in the neural systems underlying the positive symptoms of schizophrenia and drug addiction.


  • Contact Us