Implementation of team-based learning (TBL) in a second year medical school course: does prior experience with TBL improve the impact of this pedagogy?

BACKGROUND: We have shown that use of Team-based learning (TBL) in a first-year Infectious Diseases (ID) course improved final examination and course performance. Therefore, we implemented TBL in the second-year Women's Health (WH) course to improve acquisition of course content. We hypothesized that prior experience with TBL in the first-year of medical school would lead to a strong correlation between TBL performance in the first and second years. METHODS: Our study is a retrospective review of student TBL and final examination performance in the ID and WH courses. The ID course has weekly TBL exercises that cover all course material, while the WH course has one TBL that covers a small portion of the course material. Final examination and TBL individual readiness assurance test (iRAT) scores in the ID and WH courses from three classes (n = 226) were obtained with institutional review board approval. Statistical analyses were performed including comparisons of means and correlation studies. RESULTS: Average WH iRAT scores were significantly higher than ID iRAT scores (9.19 vs. 7.40,p < 0.01), and iRAT scores in both courses were highly correlated (r = 0.35,p < 0.01). When stratifying students based on WH course performance, in struggling students, iRAT but not final examination scores were higher in the WH course than the ID course (8.73 vs. 7.00,p < 0.01 and 82.45 vs. 80.51,p > 0.05, respectively). CONCLUSIONS: Our results suggest that prior experience with TBL improves TBL iRAT scores, especially in struggling students. Prior TBL experience is also associated with consistent iRAT performance between first- and second-year courses in high performing students.

Weekly team-based learning scores and participation are better predictors of successful course performance than case-based learning performance: role of assessment incentive structure.

BACKGROUND: Incentives for preparation and participation in case-based (CBL) and team-based learning (TBL) differ by virtue of differences in assessment, allowing us to evaluate the role these incentives play in preparation and participation in these activities as well as overall course performance. METHODS: Weekly TBL and CBL participation and performance as well as performance on the course final examination were recorded. Student participation was quantified and correlated with: (1) CBL preparation, participation, teamwork and completion of learning objectives scores, and (2) TBL individual readiness assurance test (iRAT) scores. RESULTS: Student final examination scores (n = 95) were more strongly correlated with TBL than CBL performance. No significant correlation was found between iRAT and CBL scores. Student participation was measured in 3 CBL groups (8 students/group) and 4 TBL teams (6 students/team). TBL participation was more strongly correlated with final examination scores than CBL participation. TBL participation was also correlated with iRAT scores. CBL scores for preparation, participation, teamwork and completion of learning objectives did not significantly correlate with iRAT scores or TBL participation. CONCLUSION: These results suggest that the assessment incentives and methods used in TBL result in student performance that better predicts performance on summative examinations.

First year medical student performance on weekly team-based learning exercises in an infectious diseases course: insights from top performers and struggling students.

BACKGROUND: In Team-Based Learning (TBL) preparation of relevant coursework during self-directed learning time is evaluated by the individual readiness assurance test (iRAT). We recently reported that student performance on iRATs is strongly correlated with final examination scores in an infectious diseases (ID) course. We now investigated how student preparation for each individual iRAT exercise relates to course performance. METHODS: Two-hundred and sixty medical students were enrolled in this three-year study. Student TBL iRAT scores were collected and correlated with final examination scores using Kruskal-Wallis One-Way ANOVA and Newman-Keul's statistical methods. RESULTS: Students performing in the upper and middle 33rd percentile on the final examination showed highly significant (p < 0.01) weekly improvements in their iRAT scores. However, students performing in the lower 33rd percentile did not show improvement in their iRAT scores until the last week of the course. Although there was a highly significant correlation between final examination and iRAT scores amongst all students participating in the study, this correlation was stronger in students performing in the lower 33rd percentile. CONCLUSIONS: Our data suggest that students who do not consistently prepare for TBL, as evidenced by low iRAT scores, exhibit poorer performance on the final examination. This lack of preparation likely interferes with the efficacy of this learning method. iRAT scores can also be used for early identification of struggling students in need of additional supports. Additionally, changes in TBL incentive structure may provide more tangible rewards for pre-class preparation in particular for struggling students.

Evaluation of the role of incentive structure on student participation and performance in active learning strategies: A comparison of case-based and team-based learning.

BACKGROUND: Student participation is important for the success of active learning strategies, but participation is often linked to the level of preparation. At our institution, we use two types of active learning activities, a modified case-based learning exercise called active learning groups (ALG) and team-based learning (TBL). These strategies have different assessment and incentive structures for participation. Non-cognitive skills are assessed in ALG using a subjective five-point Likert scale. In TBL, assessment of individual student preparation is based on a multiple choice quiz conducted at the beginning of each session. METHODS: We studied first-year medical student participation and performance in ALG and TBL as well as performance on course final examinations. RESULTS: Student performance in TBL, but not in ALG, was strongly correlated with final examination scores. Additionally, in students who performed in the upper 33rd percentile on the final examination, there was a positive correlation between final examination performance and participation in TBL and ALG. This correlation was not seen in students who performed in the lower 33rd percentile on the final examinations. CONCLUSIONS: Our results suggest that assessments of medical knowledge during active learning exercises could supplement non-cognitive assessments and could be good predictors of performance on summative examinations.

G-protein receptor kinase 5 regulates the cannabinoid receptor 2-induced up-regulation of serotonin 2A receptors.

We have recently reported that cannabinoid agonists can up-regulate and enhance the activity of serotonin 2A (5-HT2A) receptors in the prefrontal cortex (PFCx). Increased expression and activity of cortical 5-HT2A receptors has been associated with neuropsychiatric disorders, such as anxiety and schizophrenia. Here we report that repeated CP55940 exposure selectively up-regulates GRK5 proteins in rat PFCx and in a neuronal cell culture model. We sought to examine the mechanism underlying the regulation of GRK5 and to identify the role of GRK5 in the cannabinoid agonist-induced up-regulation and enhanced activity of 5-HT2A receptors. Interestingly, we found that cannabinoid agonist-induced up-regulation of GRK5 involves CB2 receptors, ß-arrestin 2, and ERK1/2 signaling because treatment with CB2 shRNA lentiviral particles, ß-arrestin 2 shRNA lentiviral particles, or ERK1/2 inhibitor prevented the cannabinoid agonist-induced up-regulation of GRK5. Most importantly, we found that GRK5 shRNA lentiviral particle treatment prevented the cannabinoid agonist-induced up-regulation and enhanced 5-HT2A receptor-mediated calcium release. Repeated cannabinoid exposure was also associated with enhanced phosphorylation of CB2 receptors and increased interaction between ß-arrestin 2 and ERK1/2. These latter phenomena were also significantly inhibited by GRK5 shRNA lentiviral treatment. Our results suggest that sustained activation of CB2 receptors, which up-regulates 5-HT2A receptor signaling, enhances GRK5 expression; the phosphorylation of CB2 receptors; and the ß-arrestin 2/ERK interactions. These data could provide a rationale for some of the adverse effects associated with repeated cannabinoid agonist exposure.

Cannabinoid receptor agonists upregulate and enhance serotonin 2A (5-HT(2A)) receptor activity via ERK1/2 signaling.

Recent behavioral studies suggest that nonselective agonists of cannabinoid receptors may regulate serotonin 2A (5-HT(2A)) receptor neurotransmission. Two cannabinoids receptors are found in brain, CB1 and CB2 receptors, but the molecular mechanism by which cannabinoid receptors would regulate 5-HT(2A) receptor neurotransmission remains unknown. Interestingly, we have recently found that certain cannabinoid receptor agonists can specifically upregulate 5-HT(2A) receptors. Here, we present experimental evidence that rats treated with a nonselective cannabinoid receptor agonist (CP 55,940, 50 µg/kg, 7 days) showed increases in 5-HT(2A) receptor protein levels, 5-HT(2A) receptor mRNA levels, and 5-HT(2A) receptor-mediated phospholipase C beta (PLCß) activity in prefrontal cortex (PFCx). Similar effects were found in neuronal cultured cells treated with CP 55,940 but these effects were prevented by selective CB2, but not selective CB1, receptor antagonists. CB2 receptors couple to the extracellular kinase (ERK) signaling pathway by Gα(i/o) class of G-proteins. Noteworthy, GP 1a (selective CB2 receptor agonist) produced a strong upregulation of 5-HT(2A) receptor mRNA and protein, an effect that was prevented by selective CB2 receptor antagonists and by an ERK1/2 inhibitor, PD 198306. In summary, our results identified a strong cannabinoid-induced upregulation of 5-HT(2A) receptor signaling in rat PFCx. Our cultured cell studies suggest that selective CB2 receptor agonists upregulate 5-HT(2A) receptor signaling by activation of the ERK1/2 signaling pathway. Activity of cortical 5-HT(2A) receptors has been associated with several physiological functions and neuropsychiatric disorders such as stress response, anxiety and depression, and schizophrenia. Therefore, these results may provide a molecular mechanism by which activation of cannabinoid receptors might be relevant to the pathophysiology of some cognitive and mood disorders in humans.

Cannabinoid agonists increase the interaction between ß-Arrestin 2 and ERK1/2 and upregulate ß-Arrestin 2 and 5-HT(2A) receptors.

We have recently reported that selective cannabinoid 2 (CB(2)) receptor agonists upregulate 5-HT(2A) receptors by enhancing ERK1/2 signaling in prefrontal cortex (PFCx). Increased activity of cortical 5-HT(2A) receptors has been associated with several neuropsychiatric disorders such as anxiety and schizophrenia. Here we examine the mechanisms involved in this enhanced ERK1/2 activation in rat PFCx and in a neuronal cell model. Sprague-Dawley rats treated with a non-selective cannabinoid agonist (CP55940, 50µg/kg, 7 days, i.p.) showed enhanced co-immunoprecipitation of ß-Arrestin 2 and ERK1/2, enhanced pERK protein levels, and enhanced expression of ß-Arrestin 2 mRNA and protein levels in PFCx. In a neuronal cell line, we found that selective CB(2) receptor agonists upregulate ß-Arrestin 2, an effect that was prevented by selective CB(2) receptor antagonist JTE-907 and CB(2) shRNA lentiviral particles. Additionally, inhibition of clathrin-mediated endocytosis, ERK1/2, and the AP-1 transcription factor also prevented the cannabinoid receptor-induced upregulation of ß-Arrestin 2. Our results suggest that sustained activation of CB(2) receptors would enhance ß-Arrestin 2 expression possibly contributing to its increased interaction with ERK1/2, thereby driving the upregulation of 5-HT(2A) receptors. The CB(2) receptor-mediated upregulation of ß-Arrestin 2 would be mediated, at least in part, by an ERK1/2-dependent activation of AP-1. These data could provide the rationale for some of the adverse effects associated with repeated cannabinoid exposure and shed light on some CB(2) receptor agonists that could represent an alternative therapeutic because of their minimal effect on serotonergic neurotransmission.

Cannabinoid 2 receptors regulate dopamine 2 receptor expression by a beta-arrestin 2 and GRK5-dependent mechanism in neuronal cells.

We have previously reported that the repeated exposure to cannabinoids upregulates and enhances the activity of serotonin 2A (5-HT2A) and dopamine 2 (D2) receptors and facilitates the formation of D2-5-HT2A receptor heterodimers in the rat prefrontal cortex and two neuronal cell lines. Because the repeated exposure to cannabinoids has been associated with adverse neuropsychiatric disorders, this study investigated the mechanisms that underly the cannabinoid-mediated regulation of D2 receptor expression in a neuronal cell model, CLU213 cells. We initially tested the effects of repeated exposure (72 h) to a non-selective cannabinoid agonist (1 nM CP55940), a selective CB1 receptor agonist (15 nM ACEA), or a selective CB2 receptor drug (1 nM GP1a) on the expression of postsynaptic D2 (D2L) receptors in CLU213 cells. Repeated CP55940, GP1a, or ACEA treatments significantly increased D2L receptor protein levels (99 % ± 7%, 30 % ± 7%, and 39 % ± 5% increases compared with control levels, respectively). Repeated exposure to both GP1a and ACEA increased D2L receptor protein levels by 73 % ± 8%. Interestingly, CP55940 and GP1a, but not ACEA, upregulated D2 mRNA. Using cells that were stably transfected with short-hairpin RNA (shRNA) lentiviral particles targeting CB2 receptors, G protein-coupled receptor kinase 5 (GRK5), and ß-arrestin 2, we found that CB2 receptors regulated D2 expression through a mechanism that is dependent on GRK5, ß-arrestin 2, and extracellular signal-related kinase (ERK)1/2. We also found that repeated exposure to either ACEA or GP1a selectively stimulated the protein and mRNA expression of GRK proteins. ACEA significantly upregulated GRK2 proteins, whereas GP1a upregulated GRK5 protein expression. Our results identified mechanisms associated with the upregulation of D2 receptors in neuronal cells after the repeated exposure to cannabinoids. These data can shed light on the mechanisms that can be targeted to prevent potential adverse effects, while simultaneously determining the therapeutic benefits of cannabinoids.

Effectiveness of a Team-Based Learning exercise in the learning outcomes of a medical pharmacology course: insight from struggling students.

We have previously reported that multiple Team-Based Learning (TBL™) exercises in a 4-week pre-clinical medical school course improved final exam performance and significantly reduced the number of course failures. Here, we conducted a long-term study, with eight cohorts of first-year medical students, to determine whether the implementation of a single TBL individual readiness assessment test (iRAT) exercise in a 4-week medical school pharmacology course produces similar effects in overall course performance. We implemented a single TBL iRAT exercise that covered the subjects addressed during one week of the medical pharmacology course, with the four most recent cohorts of students matriculating at Cooper Medical School of Rowan University (n = 403). The first four cohorts matriculating at CMSRU did not participate in the TBL exercises (n = 266). Correlation of individual student TBL iRAT and final examination scores in the medical pharmacology course was compared to a second, unrelated first-year course (physiology) to control for variation in student performance between cohorts. We found that there was a significant moderate correlation between final examination and TBL iRAT scores (r = 0.49, p < 0.01, n = 403). Interestingly this moderate correlation was seen in students performing in the lower 25th percentile on the course final examination (r = 0.41, p < 0.01, n = 101) and negligible in students performing in the upper 25th percentile (r = 0.11, n = 101, p > 0.05). Implementation of the single TBL exercise also significantly reduced variance or range of student final examination performance compared to the group of the first four cohorts. These results suggest that implementation of a single TBL exercise, which covers only one week of content delivered in a 1-month medical pharmacology course, benefits first-year medical students by reducing the disparity in knowledge acquisition among them and providing a means to identify students who may struggle with course content.

Assessment of Pathology Learning Modules With Virtual Microscopy in a Preclinical Medical School Curriculum.

OBJECTIVES: To evaluate the ability of pathology modules to promote learning of pathology-related course content in a preclinical medical education curriculum. METHODS: Pathology modules were created for the "Hematology/Oncology" and "Women's Health" (WH) courses. Students were recruited over 2 consecutive academic years; cohorts 1 and 2 refer to 2 separate groups of students in years 1 and 2, respectively, of the study. Course performance data were collected. RESULTS: Use of pathology modules resulted in a statistically significant higher correlation between performance on the final examination and pathology-related questions in the Hematology/Oncology course and written examination and pathology-related questions in cohort 1 in the WH course. There was statistically significant improvement (P = .026) on pathology-related laboratory practical examination questions in the WH course for cohort 1, and no other statistically significant improvement for the other cohorts and examinations. The percentage of students completing all or part of the modules was highest in the WH course for cohort 1 (60%) compared with WH course cohort 2 (33%) and Hematology/Oncology cohort 1 (30%) and cohort 2 (39%). CONCLUSIONS: Pathology modules may improve acquisition and retention of pathology-related course content when used appropriately.

A Novel Grading Strategy for Team-Based Learning Exercises in a Hands-on Course in Molecular Biology for Senior Undergraduate Underrepresented Students in Medicine Resulted in Stronger Student Performance.

We developed a hands-on course in molecular biology for undergraduate underrepresented in medicine (URM) students. To incentivize student preparation for team-based learning (TBL) activities, we implemented a novel grading schema that requires a minimum individual readiness assurance test (iRAT) score to share the team group readiness assurance test (gRAT) score. Fifty-one students participated in this 2-year study and were divided in teams of five or six students that worked throughout the course on a unique, hands-on project and also participated in TBL exercises. In the laboratory sessions, students isolated RNA from cultured neuronal cells, synthesized complementary DNA (cDNA), and used gene sequencing to identify a gene relevant in human health and disease. Student participation in TBL was quantified and correlated with performance on individual iRATs and the course final examination. We found that implementation of the novel incentive structure lowered the variance of TBL scores (iRAT and gRAT) and strengthened the correlation between final examination scores and either iRAT scores or percentage participation in TBL. Subgroup analysis showed that with the new grading schema, stronger students benefited more from the gRAT exercises, while more poorly performing students were better helped by individual preparation prior to the iRAT exercise. A combination of two active learning strategies, TBL and hands-on sessions, may strengthen student acquisition of course content and promote teamwork skills. The new incentive structure seems to reduce the disparity in knowledge amongst our students as demonstrated by the reduced iRAT and gRAT score variances. © 2018 International Union of Biochemistry and Molecular Biology, 47(2): 115-123, 2019.

Participation in Active Learning Correlates to Higher Female Performance in a Pipeline Course for Underrepresented Students in Medicine.

This study was designed to explore the relationship between participation (measured by percentage of time spoken) in team-based learning (TBL) exercises and final examination in a 4-week medical microbiology course for college students from backgrounds underrepresented in medicine (URM). A significant correlation was found between participation and examination scores in lower performing students. Although male participation was higher, a significant correlation between participation and examination scores was found only in females. These data suggest that female participation is based on knowledge of the subject under discussion and that affirmation in TBL positively reinforces self-confidence, increasing student's efficiency during peer teaching.

Implementation of Team-Based Learning: a Tale of Two New Medical Schools.

Team-based learning (TBL) is gaining popularity at medical schools transitioning from lecture-based to active learning curricula. Here, we review challenges and opportunities faced in implementing TBL at 2 new medical schools. We discuss the importance of using meaningful TBL grades as well as the role TBL plays in developing critical reasoning skills and in early identification of struggling students. We also discuss how the concurrent use of learning strategies with different incentive structures such as problem- and case-based learning could foster the development of well-rounded physicians. We hope this monograph helps and even inspires educators implementing TBL at their schools.

A Novel Tool for Problem-Based Learning Case Review.

The success of problem-based learning (PBL) depends on case quality and facilitator preparation. We developed a literature-based tool, the R2ICE form, to improve faculty case review. Its implementation and survey of end users showed the tool was expedient and advantageous. Literature-based tools can guide PBL construction and improve case development.

Sustained treatment with a 5-HT(2A) receptor agonist causes functional desensitization and reductions in agonist-labeled 5-HT(2A) receptors despite increases in receptor protein levels in rats.

Adaptive changes in serotonin2A (5-HT(2A)) receptor signaling are associated with the clinical response to a number of psychiatric drugs including atypical antipsychotics and selective serotonin reuptake inhibitors. The present study examined possible mechanisms of agonist-induced desensitization of 5-HT(2A) receptors in rat hypothalamic paraventricular nucleus (PVN) after 4 and 7 days of treatment with 1mg/kg (-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI). The magnitude of 5-HT(2A) receptor-mediated oxytocin release decreased 78% after 4 days and 61% after 7 days of DOI treatment. Similarly, the magnitude of ACTH release following 1mg/kg DOI decreased by 31% after 4 days and 38% after 7 days of DOI treatment. Treatment with DOI for either 4 or 7 days caused a significant decrease (by approximately 50%) in the high-affinity 5-HT(2A) receptor binding as measured by (125)I-DOI binding compared to saline-treated control rats. In contrast, western blot analysis demonstrated a significant increase in 5-HT(2A) receptor protein levels with 4 or 7 days of DOI treatment to 167% and 191% of control levels, respectively. Real time quantitative RT-PCR analysis revealed a small but nonsignificant increase in the levels of 5-HT(2A) mRNA following treatment with DOI for 4 or 7 days. Taken together, the 5-HT(2A) receptor-stimulated hormone responses, agonist binding data and western blot data suggest that although agonist treatment increases the levels of 5-HT(2A) receptor protein in the cell membrane, there is a reduction in the population of 5-HT(2A) receptors capable of high-affinity binding and mediating a functional response.

Withdrawal from a single exposure to cocaine increases 5-HT2A receptor and G protein function.

We previously reported that withdrawal from chronic cocaine produces supersensitivity of serotonin 2A receptors. We report here the minimum cocaine exposure necessary to produce withdrawal-associated increases in serotonin 2A receptor signaling in the frontal cortex. Rats withdrawn from cocaine treatments of 1, 3 or 7 days exhibited increases in G protein-stimulated and serotonin 2A receptor-stimulated phospholipase C activity in the frontal cortex. A single cocaine injection produced withdrawal-induced changes comparable to that produced by repeated exposure. None of these cocaine treatment paradigms are associated with changes in the levels of serotonin 2A receptors, Galphaq or Galpha11 proteins. These data demonstrate that only a single exposure to cocaine can produce unique withdrawal-associated neuroadaptations in serotonin 2A receptor signaling in the frontal cortex, which may be clinically relevant with respect to drug relapse.

5-HT1A receptors mediate (+)8-OH-DPAT-stimulation of extracellular signal-regulated kinase (MAP kinase) in vivo in rat hypothalamus: time dependence and regional differences.

Brain serotonin 1A (5-HT1A) receptors play an important role in mood disorders and can modulate various intracellular signaling mechanisms. We previously reported that systemic administration of either full or partial 5-HT1A agonists increases neuroendocrine responses and that tandospirone, an azapirone partial agonist, can activate (phosphorylate) extracellular signal-regulated kinase (ERK) in the hypothalamic paraventricular nucleus (PVN). In contrast, decreased levels of phosphoERK (pERK) have been reported in hippocampus following in vivo administration of either azapirone or aminotetralin 5-HT1A agonists, such as 8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT). The present study investigated the time-dependent activation of MAP kinase in hypothalamus by (+)8-OH-DPAT to determine the regional differences and receptor specificity of the changes in pERK. Adult male rats received a systemic injection of (+)8-OH-DPAT (200 microg/kg, s.c.). The time-dependent changes in ERK activation were examined in hypothalamic nuclei as well as other brain regions associated with modulation of mood. (+)8-OH-DPAT produced a rapid increase (at 5 min) and transient return (at 15 min) of pERK levels in PVN and medial basal hypothalamus. In contrast, pERK levels in hippocampus were reduced at both 5 and 15 min after (+)8-OH-DPAT. Pretreatment with the 5-HT1A receptor-specific antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide (WAY100635) completely blocked the (+)8-OH-DPAT-mediated changes in pERK levels in PVN, medial basal hypothalamus, and hippocampus. No significant (+)8-OH-DPAT-induced changes in pERK were observed in dorsal raphe or amygdala. In conclusion, these results demonstrate that 8-OH-DPAT activation of MAP kinase signaling in vivo is a transient and region-specific phenomenon and in rat hypothalamus and hippocampus is mediated by 5-HT1A receptors.

Evidence that 5-HT2A receptors in the hypothalamic paraventricular nucleus mediate neuroendocrine responses to (-)DOI.

The present study determined whether the serotonin2A (5-HT2A) receptors in the hypothalamic paraventricular nucleus mediate the neuroendocrine responses to a peripheral injection of the 5-HT2A/2C receptor agonist (-)DOI [(-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane]. The 5-HT2A receptor antagonist MDL100,907 ((+/-)-alpha(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidinemethanol), the 5-HT2C receptor antagonist SB-242084 (6-chloro-5-methyl-1-[[2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-indoline), or vehicle were microinjected bilaterally through a chronically implanted double-barreled cannula into the hypothalamic paraventricular nucleus 15 min before a peripheral injection of (-)DOI in conscious rats. (-)DOI significantly elevated plasma levels of oxytocin, prolactin, ACTH, corticosterone, and renin. Neither the 5-HT2A receptor antagonist nor the 5-HT2C receptor antagonist, injected alone, altered the basal levels of these hormones. MDL100,907 (0.748, 7.48, and 18.7 nmol) dose dependently inhibited the (-)DOI-induced increase in all of the hormones except corticosterone. In contrast, SB-242084 (10 nmol) did not inhibit (-)DOI-increased hormone levels. To confirm the presence of 5-HT2A receptors in the hypothalamic paraventricular nucleus, 5-HT2A receptors were mapped using immunohistochemistry. Densely labeled magnocellular neurons were observed throughout the anterior and posterior magnocellular subdivisions of the hypothalamic paraventricular nucleus. Moderately to densely labeled cells were also observed in parvicellular regions. Thus, it is likely that 5-HT2A receptors are present on neuroendocrine cells in the hypothalamic paraventricular nucleus. These data provide the first direct evidence that neuroendocrine responses to a peripheral injection of (-)DOI are predominantly mediated by activation of 5-HT2A receptors in the hypothalamic paraventricular nucleus.

Paroxetine is effective in desensitizing 5-HT1A receptor function in adult offspring exposed prenatally to cocaine.

RATIONALE: Desensitization of postsynaptic 5-HT(1A) receptors may be responsible for the therapeutic effectiveness of serotonin selective uptake inhibitors (SSRIs). As prenatal cocaine exposure produces long-term deficits in 5-HT neurons in offspring, it may alter the ability of postsynaptic 5-HT(1A) receptors to be desensitized by chronic paroxetine. OBJECTIVES: The aim of the study is to determine (1) prenatal cocaine-induced changes in 5-HT(1A) receptor function and (2) the effectiveness of chronic treatment with paroxetine to produce 5-HT(1A) receptor desensitization in adult offspring exposed to cocaine in utero. METHODS: Pregnant rats received saline or (-)cocaine (15 mg/kg, s.c.) twice daily from gestational days 13 through 20. Adult male offspring from each of prenatal groups were treated with saline or paroxetine (10 mg/kg/day; i.p.) for 14 days. Eighteen hours post-treatment, rats were challenged with saline or the 5-HT(1A) receptor agonist (+)8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.04 or 0.2 mg/kg, s.c.). Plasma oxytocin, adrenocorticotropic hormone (ACTH), corticosterone, renin and prolactin were determined. RESULTS: Prenatal cocaine exposure did not alter 5-HT(1A) receptor-mediated neuroendocrine responses. Paroxetine treatment desensitized 5-HT(1A) receptor-mediated increases in oxytocin, ACTH and corticosterone to a comparable extent in all offspring and reduced the E(max) for ACTH only in prenatal cocaine-exposed offspring. Cortical [(3)H]-8-OH-DPAT- or [(3)H]-WAY100635-labeled 5-HT(1A) receptors were unaltered by prenatal cocaine or subsequent paroxetine treatment. CONCLUSIONS: Postsynaptic 5-HT(1A) receptor function is unaltered by prenatal cocaine exposure and paroxetine can effectively desensitize 5-HT(1A) receptor function in adult cocaine-exposed offspring. These data suggest that paroxetine may be clinically effective in treating mood disorders in adults exposed in utero to cocaine.

Chronic mild stress induces behavioral and physiological changes, and may alter serotonin 1A receptor function, in male and cycling female rats.

RATIONALE: Interactions among stress, serotonin 1A (5-HT(1A)) receptors, and the hypothalamic-pituitary-adrenocortical (HPA) system have been proposed to influence the development of depression in humans. The investigation of depression-relevant behaviors and physiological responses to environmental stressors in animal models of depression may provide valuable insight regarding these mechanisms. OBJECTIVES: The purpose of these experiments was to investigate the interactions among central 5-HT(1A) receptors, endocrine function, and behavior in an animal model of depression, chronic mild stress (CMS). METHODS: The current study examined behavioral responses to a pleasurable stimulus (sucrose), estrous cycle length (in female rats), and plasma hormone levels following systemic administration of a selective 5-HT(1A) receptor agonist [(+)8-hydroxy-N,N-dipropyl-2-aminotetralin hydrobromide (8-OH-DPAT); 40 mug/kg, s.c.; administered 15 min prior to sacrifice], in male and female rats exposed to 4 weeks of CMS. RESULTS: Four weeks of CMS produced a reduction in the intake of 1% sucrose (anhedonia), as well as attenuated adrenocorticotropic hormone (ACTH) responses to 8-OH-DPAT in both male and female rats (22 and 18% lower than the control groups, respectively). Corticosterone and oxytocin responses to 8-OH-DPAT were not altered by exposure to CMS. In female rats, CMS induced a lengthening of the estrous cycle by approximately 40%. CONCLUSIONS: CMS produces minor HPA disruptions along with behavioral disruptions. Alterations in 5-HT(1A) receptor function in specific populations of neurons in the central nervous system may be associated with the CMS model. The current findings contribute to our understanding of the relations that stress and neuroendocrine function have to depressive disorders.