Investigating the Dose and Voltage Dependent Effects of the Herbal Antiepileptic Huperzine A at Different Subunits of the NMDA Receptor
Christine Arsnow (Neuroscience)
Advisor: Nancy Kleckner
N-methyl D-aspartate (NMDA) receptors are ionotropic glutamate receptors that contribute to excitatory neurotransmission throughout the central nervous system. The NMDA receptor is composed of two types of subunits, an NR1 and NR2, which form a nonselective cation channel. NR2 subunits are further subdivided into types NR2A-D, each of which imparts subtle functional differences to receptors. Hyperactivity of NMDA receptors causes neurological disorders such as stroke and epilepsy. As a result, NMDA receptor inhibitors are often used to prevent excitotoxicity arising from these conditions. Huperzine A, an alkaloid isolated from Chinese club moss Huperzia serrata, is a centuries-old herbal cure for epilepsy. Research has revealed that Hup A exerts its antiepileptic effects by blocking the NMDA receptor via an unspecified mechanism. Evidence for binding activity similar to polyamines, MK-801 and PCP exists, but is not definitive. The current experiment uses various receptor subunits expressed in Xenopus laevis oocytes to investigate the subunit specificity and mechanism of action of HupA. This knowledge will help predict the side effects and pharmacological interactions of HupA, and thus provide information relevant to its therapeutic use.
Orbitofrontal Cortex Correlate of Impulsivity and Goal-Directed Behavior in Bipolar I, Schizophrenia, and Schizoaffective Disorder
Gina Capalbo (Neuroscience)
Advisor: Nancy Koven
Differential diagnosis between bipolar I and schizophrenia has always been a problem in the field of psychology and psychiatry. Problems with differential diagnosis between bipolar I and schizophrenia has lead to the diagnosis of schizoaffective disorder, which has components of both bipolar I and schizophrenia. Both bipolar I disorder and schizophrenia have been associated with structural and functional abnormalities of the orbitofrontal cortex (OFC). Objective: the present study seeks to measure volumetric similarities of OFC between bipolar I, schizophrenia, and schizoaffective patients. Furthermore, to identify relationships between volumetry and neuropsychological performance. Methods: Structural MRI and neuropsychological data were collected and obtained via manual tracing on SPGR images (124 1-mm slices acquired on a GE 1.5T scanner) in 3-D slicer. Results: no significant difference was found across groups in OFC volumetry and neuropsychological assessments. Although, male bipolar patients have a larger right OFC in comparison to female bipolar patients. Conclusion: Qualitative analysis of the data may suggest of a pattern of severity in symptoms and cognitive performance. Bipolar 1disorder having the most severe symptoms and cognitive performance, than schizoaffective, than schizophrenia. This pattern may show that bipolar 1, schizophrenia, and schizoaffective are on a continuum and may not be three distinct disorders.
The Opioid Receptor Antagonist, Naltrexone, and the Kappa Receptor Agonist, U50,488, Reduce L-DOPA-Induced Dyskinesia in an Animal Model of Parkinson’s Disease
Jared John Cassin (Neuroscience-Honors)
Advisor: John Kelsey
While levodopa (L-DOPA) is currently the most effective therapy for Parkinson’s disease (PD), it is also associated with the development of L-DOPA-induced dyskinesia (LID). Because the endogenous opioids, dynorphin and enkephalin, upregulate in response to L-DOPA in striatal neurons of the direct and indirect pathway of the basal ganglia, respectively, they have been implicated in LID. This study sought to help clarify the role of endogenous opioids in PD and LID by investigating the effects of the nonspecific opioid receptor antagonist, naltrexone (1, 4, and 10 mg/kg), and the specific κ opioid receptor agonist, U50,488 (0.3, 1, and 3 mg/kg) on LID and the antiparkinsonian effect of L-DOPA in the unilateral 6-OHDA rat model of PD. A high dose of L-DOPA (35 mg/kg) was used to produce LID as measured by the abnormal involuntary movements (AIMs) rating scale. Moderate doses of naltrexone (4 and 10 mg/kg) improved the antiparkinsonian response to L-DOPA as measured by forepaw stepping, and 1 and 10 mg/kg naltrexone tended to reduce LID. Furthermore, U50,488 (1 and 3 mg/kg) reduced LID and tended to enhance the therapeutic effect of L-DOPA on stepping. Together, these results suggest that naltrexone and U50,488 may be useful in treating PD patients with LID, and that naltrexone may also help ameliorate parkinsonian symptoms in conjunction with L-DOPA.
Propranolol does not Interfere with the Reconsolidation of a Cocaine-Induced Taste Aversion to Saccharin
Brittany Clement (Neuroscience)
Advisor: John Kelsey
While memories are assumed to undergo an initial consolidation process, at least some memories may also undergo an additional reconsolidation process after they have been reactivated. Understanding how to interfere with this reconsolidation may have therapeutic benefits, including the reduction of cue-drug memories that lead drug addicts to relapse into drug taking. The current study investigated whether a taste-drug memory undergoes a process of reconsolidation. Rats initially developed an aversion to the taste of saccharin after six pairings with cocaine. One day after conditioning, rats were reexposed to saccharin without (Experiment 1) or with (Experiment 2) a cocaine injection to reactivate the taste-drug memory, and propranolol (a drug shown to interfere with the reconsolidation of other memories) or saline was administered. The following day, the strength of the taste-drug memory was assessed in a two-bottle test to measure if the rats were still reluctant to drink saccharin. Rats given propranolol following reactivation, without (Experiment 1) or with (Experiment 2) an injection of cocaine, drank the same amount of saccharin on the subsequent test days as rats injected with saline, suggesting that propranolol did not interfere with the reconsolidation of a weakly (Experiment 1) or strongly (Experiment 2) reactivated saccharin-cocaine memory. Further research using a modified paradigm will be required to determine if a taste-drug memory can undergo reconsolidation.
The CB1 Antagonist Rimonabant Improves Forepaw Stepping in an Animal Model of Parkinson’s Disease
Owen Harris (Neuroscience)
Advisor: John Kelsey
Parkinson’s disease (PD) is associated with an upregulation of the cannabinoid CB1 receptors in the basal ganglia, an upregulation that is reduced by L-DOPA therapy. In order to better understand the role of this upregulation, we examined the effects of systemic injections of the specific CB1 antagonist, rimonabant, on the unilateral 6-OHDA rat model of PD. Male Long-Evans rats were injected into the left medial forebrain bundle with 12 µg of the specific dopamine neurotoxin 6-OHDA, which generates a long lasting deficit in contralateral forepaw stepping. Injections of .05 to 1, but not .01, mg/kg rimonabant improved, but did not normalize, forepaw stepping with the impaired contralateral forepaw without affecting unimpaired ipsilateral forepaw stepping. The optimal dose was .05 mg/kg, which improved contralateral stepping by 33%. This dose of rimonabant also enhanced the therapeutic effect of 8 mg/kg L-DOPA on contralateral stepping These data indicate that the upregulation of CB1 receptors during PD play a role in the disease and suggest that CB1 antagonists such as rimonabant may be useful as mono- or adjunctive therapy.
Pharmacological classification of Glu R 5,6,7 immunoreactive neurons in the buccal ganglia of the pond snail, Helisoma trivolvis
Peter Klein (Neuroscience)
Advisor: Nancy Kleckner
Glutamate plays a crucial role in regulating the triphasic central pattern generator (CPG) responsible for feeding in the pond snail, Helisoma trivolvis. This CPG is composed of groups of neurons in subunits S1, S2 and S3 within the buccal ganglia. The ordered firing of these subunits causes the protraction, retraction and hyperretraction, respectively, of the file-like odontophore that scrapes food from the substrate and moves it into the esophagus. Stimulation of the S2 interneuron B2, which is thought to be glutamatergic, stimulates firing in S2 motorneurons, while at the same time inhibiting S1 and S3 motorneurons. The application of glutamate to buccal ganglia mimics B2 stimulation, while the application of the glutamate antagonist CNQX to B2 is sufficient to disrupt the rhythmicity of the CPG. Previous studies employed a fluorescently labeled GluR5,6,7 monoclonal antisera to the buccal ganglia and identified a group of neuron cell bodies on the dorsal surface, medial to B5, which showed highly specific immunoreactivity for this kainic acid (KA) receptor subunit. The neurons in this region have not been previously studied and do not include S2 motorneurons previously known to be stimulated by glutamate. What role, if any, they play in the feeding CPG is not yet known. This study aimed to characterize the neurons in this region through measuring changes in membrane potential and action potential rates of GluR5,6,7 immunoreactive neurons when exposed to glutamate, the AMPA/KA receptor agonist kainic acid and the metabotropic glutamate receptor agonist quisqualate. Results indicate that the response of individual neurons in this region to the glutamate agonists is somewhat varied. Several of the neurons in the immunoreactive regions displayed electrophysiological responses to the agonists that were characteristic of AMPA/kainate-like receptors. These immunoreactive neurons also displayed characteristic properties that resembled vertebrate mGluRs. This demonstrates that a wide range of receptor sub-types are likely present in Helisoma and indicates that the neurons in the immunoreactive region likely are motor neurons involved in the CPG for feeding behavior.
Characterization of Potassium Channels Implicated in Glutamate Induced Inhibition of Neurons B5, B6, B7, B8, and B19 in Helisoma trivolvis
Mike Palmer (Neuroscience)
Advisor: Nancy Kleckner
Glutamate has been implicated as a critical neurotransmitter within vertebrate as well as invertebrate species. Glutamate modulates motor neuron firing within the buccal ganglia of model organism Helisoma trivolvis and is responsible for the organism’s triphasic feeding pattern. Glutamate excites motorneurons within the phase 2 (S2) and has been shown to simultaneously inhibit phase 1 (S1) and phase 3 (S3) motorneurons. While glutamate excitation is thought to occur through opening of AMPA/KA type glutamate receptors, allowing sodium to enter and depolarize cells, the mechanism by which glutamate inhibits motorneuron in S1 and S3 is unknown. This project utilized electrophysiological and pharmacological techniques as well as visual staining methods to help characterize the mechanism of glutamate induced inhibition of S1 and S3 buccal motorneurons. The presence of inhibitory GluRs was confirmed on S1 motor neurons B6 and B8. Inhibitors of G-protein mediated potassium channels such as spermine and tertiapin-Q, as well as general voltage dependent potassium channel inhibitors such as TEA and 4-AP, were administered to determine whether the glutamate mediated mechanism of inhibition involves activation of potassium channels. Experiments indicate that while TEA and 4-AP have been shown to stimulate firing within buccal motor neurons they do not block glutamate-mediated hyperpolarization in neurons B5 and B19. Kir subtype GIRK1/4 blocker tertiapin-Q and Kir2 subtype spermine induced inhibition in B19 neurons and failed to block glutamate induced inhibition. This suggests that potassium channels involved in glutamate-mediated hyperpolarization must be insensitive to these blockers and if these channels are mGluR must be of a different subtype. Future research using isolated neurons and different Kir family subtype blockers to further the characterization of the GluRs responsible for glutamate induced hyperpolarization in Helisoma. Knowledge of the mechanism of glutamate induced inhibition of motor neurons in Helisoma trivolvis buccal ganglia will provide information about the role of glutamate in feeding, and can be extrapolated to better understand pattern generated cellular communication within other invertebrate as well as vertebrate organisms.
The Role of the Inferior Parietal Lobe in Schizophrenia: Unawareness and Lack of Insight
Lucia M. Piacenza (Neuroscience)
Advisor: Nancy Koven
A surprisingly large number of patients with schizophrenia demonstrate unawareness of their illness. There is likely room to improve the treatment of schizophrenia by tackling the concept of awareness. Unaware patients with schizophrenia are often resistant to confrontation about their illness or symptoms, which makes treatment efforts profoundly difficult. The neurological basis of impaired insight in schizophrenia is as yet unknown. The parietal lobe is known to play a role in general anosognosia, so it is possible the circuitry involved in awareness in schizophrenia is embedded in the connections between the frontal and parietal lobes. This study focuses on the volumetry of the right inferior parietal lobe (IPL) in aware (n=4) versus unaware schizophrenic patients (n=4) (as determined by relative scores on the Scale to Assess Unawareness of Mental Disorders) and controls (n=9). Inferior parietal lobe volume and awareness were expected to have a direct relationship: as lobe volume decreases, so should awareness. Results indicated no correlation between IPL volume and level of awareness, and no difference in IPL volume in patient versus control subjects. While these results appear to disprove the involvement of the IPL in monitoring awareness in psychosis, it is possible that volumetric measurement could not clearly explain the role the IPL plays. Shape analysis of the IPL, specific DTI studies of white matter connections between the frontal lobe and IPL, and functional imaging studies could solidify the role the IPL plays on monitoring schizophrenia-specific neurological anosognosia, and indicate a focus of research to develop more effective treatment of schizophrenia.
Medial Septal Lesions Tend to Enhance Locomotor Sensitization to Nicotine in Rats
Liana Schapiro (Neuroscience)
Advisor: John Kelsey
Repeated exposure to nicotine in rats causes sensitization, which is behaviorally evident in increased locomotion. Lesions of the medial septal n. enhance locomotor sensitization to amphetamine and enhance the conditioned place preference produced by cocaine. The purpose of this study was to discover if lesions of the medial septal n. would enhance the development or expression of locomotor sensitization to nicotine. Rats given 0.4 mg/kg nicotine increased locomotion over sessions, and the rats with septal lesions locomoted more than the sham-operated controls. In response to subsequent challenge injections of nicotine, the lesioned rats tended to be more active than the controls only if both groups had been previously sensitized to nicotine. Moreover, a challenge injection of 0.4 mg/kg nicotine tended to increase locomotion more in the previously sensitized rats than in the non-sensitized rats only if the rats also had septal lesions. These results indicated that prior sensitization to nicotine tended to enhance the locomotor response to challenge injections in lesioned rats more than in sham controls. These findings are consistent with the hypothesis that septal lesions enhance the reward value of a variety of addictive drugs.
The Opiate Kappa Receptor Antagonist, nor-BNI, Reduces the Aversiveness of Opiate Withdrawal in Rats
Kathryn Condel Schierberl (Neuroscience- Honors)
Advisor: John Kelsey
Dynorphin, an endogenous opiate, has been implicated in the anti-rewarding effects of repeated administration of various drugs of addiction and therefore might be expected to enhance the aversiveness of opiate withdrawal. Because the vast majority of the effects of dynorphin are due to its selective binding to kappa-opioid receptors, I tested this hypothesis by examining the ability of nor-BNI, a selective kappa-receptor antagonist, to reduce the aversiveness of opiate withdrawal in rats. Morphine dependence was induced by escalating twice per day injections, over the course of 5.5 days, concluding with a dose of 50 mg/kg. On the morning of day 6 rats were injected with either saline or 20 mg/kg nor-BNI 5 hr prior to 4 mg/kg naltrexone-precipitated withdrawal. Nor-BNI reduced the feces excreted during withdrawal and reduced the conditioned place aversion to the chamber in which withdrawal occurred. These data, are, thus, consistent with the hypothesis that dynorphin, by acting on kappa receptors, does enhance the aversiveness of opiate withdrawal.
Neuropsychological Correlates of Executive Dysfunction in Alexithymia
Whitney L. Thomas (Neuroscience)
Advisor: Nancy Koven
Difficulty attending to and distinguishing among emotions are two aspects of the alexithymia construct. Etiological theories of alexithymia include frontal lobe impairment, which would suggest corresponding weaknesses in executive functioning. Although some studies have identified isolated cognitive deficits in alexithymics, no study to date has systematically investigated executive functioning in this population while simultaneously deconstructing the alexithymia construct into empirically-derived dimensions. Participants in Study 1 completed self-report surveys of alexithymia as well as a neuropsychological measure of executive functioning. Principal components analysis revealed two alexithymia-related factors: Emotional Monitoring (EM) and Emotional Clarity (EC). Subsequent analyses revealed that low EC participants performed worse than high EC participants across multiple executive function domains. No relationship was found between EM and patterns of cognitive performance. These data further suggest frontal lobe abnormality in alexithymia when specifically considering the EC aspect of the construct. Subsequent neuropsychological tests were administered to corroborate these results. Thirty participants from Study 1 (15 high EC and 15 low EC) were invited back to complete a battery of neuropsychological tests. Executive functions of interest were response inhibition, set-shifting, self-monitoring, task initiation, working memory, and planning. Contradictory to the hypothesis, there were no significant effects of alexithymia status on executive functioning. However, post-hoc analyses revealed three trends, suggesting that high levels of self-reported emotional clarity is related to verbal and non-verbal fluency abilities as well as behavioral consistency. Because neither fluency nor behavioral consistency were among the targeted executive functions in Study 2, additional research is required to substantiate these findings.
6-OHDA Lesion of the Medial Prefrontal Cortex as an Animal Model of the Negative Symptoms of Schizophrenia
Lincoln Tirpaeck (Neuroscience)
Advisor: John Kelsey
Schizophrenia is an incapacitating mental disorder known to affect approximately one percent of the world’s population. The amended dopamine hypothesis in conjunction with observed hypofrontality in schizophrenic patients suggests that cognitive and negative symptoms are derived from insufficient dopamine activation in the prefrontal cortex, which in turn, leads to hyperactivation of dopamine subcortically and consequential expression of positive symptoms. This study examined the effect of 6-hydroxydopamine (6-OHDA) lesions of the mPFC on locomotion and exploratory behavior in the hole board apparatus (HBA), as locomotion has been used as a measure of positive symptom expression (Beninger, 1983), and exploratory behavior in the HBA has been shown to reflect negative symptomology (Morita et al., 2000). A high (12 mg) or a low (4 mg) concentration of the selective dopamine neurotoxin 6-OHDA was injected bilaterally into the mPFC of male adult rats. The large lesion tended to reduce baseline locomotor behavior and had no effect on head dipping in the HBA, whereas the small lesion tended to decrease head dipping while having no effect on locomotor behavior. Furthermore, both the large and the small lesion eliminated PCP-induced locomotion. The small lesion was also found to enhance baseline locomotor activity in an open field test. These results are somewhat consistent with previous 6-OHDA models, and suggest that the positive and negative symptoms of schizophrenia may be rooted in reduced DA transmission in the mPFC, as is predicted by the amended DA hypothesis.