Shared Medical Appointment: A Novel Model for Incorporating Group Visits Into Residency Training for Substance Use Disorders

BACKGROUND

Shared medical appointments (SMAs) are a novel modality for treating patients with similar conditions, together, by a team of interdisciplinary providers. SMAs benefit patients with substance use disorder (SUD), but no research has focused on the feasibility of implementation of SMAs in a teaching clinic.

METHODS

Primary care residents rotated in a half-day ambulatory addiction clinic for 4 weeks where a third-year resident co-facilitated 4 SMAs. Confidence, knowledge, and attitudes about SUD care were assessed using web-based surveys at weeks 0, 4, and 8. Pre- and post-intervention scores were compared using a t test for paired samples.

RESULTS

Ten residents were included in the analyses. Using a 10-point Likert scale, confidence in SUD knowledge (7.0-8.3, P = .003), confidence in counseling patients with SUD (7.1-8.2, P = .023), and confidence in facilitating an SMA (5.7-8.3, P = .007) showed statistically significant increases from baseline following exposure to the SMAs. Confidence that counseling and other treatments will make a difference for patients with illicit drug use increased (7.1-8.0, P = .142), but did not differ statistically. Furthermore, on a 4-point Likert scale, understanding of behavioral therapies for treating and preventing the relapse of SUD (2.9-3.2, P = .180) showed a similar increase. Attitudes toward patients with SUD (42.4-42.1, P = .303) and physician empathy (119.3-119.2, P = .963) did not change from pre- to post-intervention.

CONCLUSIONS

SMAs are a feasible training tool in the education of primary care residents on an addiction medicine rotation. Residents develop confidence co-facilitating SMAs after 4 weeks. Overall, exposure to SMAs during residency can provide an opportunity to increase confidence in treating patients with SUD, as well as provide a training modality that may shift the way residents interact with patients receiving SUD treatment.

Preparing Physicians to Treat Addiction: Inclusion of Dedicated Addiction Training During Internal Medicine Residency

BACKGROUND

Physicians in internal medicine lack comfort and skills required to diagnose and treat substance use disorder (SUD). Formal training in substance use treatment within primary care training has traditionally been inconsistent and sparse. The purpose of this study is to assess the impact of a longitudinal experiential addiction curriculum on the attitudes and experiences of graduates from a primary care/internal medicine residency program that included formal addiction didactics, rotations in an outpatient addiction clinic embedded within the resident primary care clinic, and exposure to addiction medicine faculty across treatment settings.

METHODS

A survey was emailed to all graduates from a single academic primary care residency program who graduated between 2016 and 2018 (n = 53). The survey assessed pharmacotherapy for SUD prescribing patterns, comfort with SUD pharmacotherapy, overall comfort treating SUD, experience correcting stigmatizing language, and providing guidance to colleagues on the care of patients with SUD. A subset of respondents (n = 14) were interviewed regarding their experience with the residency program's addiction medicine curriculum and its impact on their current clinical practice.

RESULTS

Sixty percent (n = 28) of graduates responded to the survey. All respondents felt comfortable using medications to treat SUD. Eighty-four percent perceived themselves as more comfortable using pharmacotherapy to treat SUD than their colleagues. Qualitative interviews revealed that this addiction medicine training shaped participants' attitudes toward patients with SUD and imparted them with the skills to address stigmatizing language. Participants described how they have become ambassadors of addiction medicine in their workplace and a resource to colleagues with less comfort in the management of SUD.

CONCLUSION

Graduates of a primary care/internal medicine residency with a dedicated addiction medicine curriculum are comfortable prescribing pharmacotherapy for SUD, taking an active role in reducing SUD-related stigma, and serving as a resource for colleagues.

Chief resident behaviors that lead to effective morning reports, a multisite qualitative study

BACKGROUND

Morning report is a fundamental component of internal medicine training and often represents the most significant teaching responsibility of Chief Residents. We sought to define Chief Resident behaviors essential to leading a successful morning report.

METHODS

In 2016, we conducted a multi-site qualitative study using key informant interviews of morning report stakeholders. 49 residents, Chief Residents, and faculty from 4 Internal Medicine programs participated. Interviews were analyzed and coded by 3 authors using inductive reasoning and thematic analysis. A preliminary code structure was developed and expanded in an iterative process concurrent with data collection until thematic sufficiency was reached and a final structure was established. This final structure was used to recode all transcripts.

RESULTS

We identified four themes of Chief Resident behaviors that lead to a successful morning report: report preparation, delivery skills, pedagogical approaches, and faculty participation. Preparation domains include thoughtful case selection, learning objective development, content editing, and report organization. Delivery domains include effective presentation skills, appropriate utilization of technology, and time management. Pedagogical approach domains include learner facilitation techniques that encourage clinical reasoning while nurturing a safe learning environment, as well as innovative teaching strategies. Moderating the involvement of faculty was identified as the final key to morning report effectiveness. Specific behavior examples are provided.

CONCLUSION

Consideration of content preparation, delivery, pedagogical approaches, and moderation of faculty participation are key components to Chief Resident-led morning reports. Results from this study could be used to enhance faculty development for Chief Residents.

The Spectrum of Alcohol Use: Epidemiology, Diagnosis, and Treatment

In the United States, alcohol is the most common substance used and the spectrum of unhealthy alcohol use is highly prevalent. Complications of unhealthy alcohol use affect nearly every organ system. One of the most frequent and potentially life-threatening of these complications is alcohol withdrawal syndrome for which benzodiazepines remain first-line therapy. Pharmacologic treatment of alcohol use disorder, the most severe form of unhealthy alcohol use, is underutilized despite the availability of multiple effective medications. Although behavioral therapies are an important component of treatment, they are overemphasized at the expense of pharmacotherapy.

Physicians Should Play a Role in Ensuring Safe Firearm Ownership

The USA is unique among industrialized nations in its dramatic rate of firearm violence. Unfortunately, firearm-related issues in America are politically divisive and fraught with controversy, thus impeding the study and implementation of safety strategies. Despite the lack of consensus, there is agreement that firearms should be kept away from individuals with criminal intent and those who are dangerous due to medical impairment. While predicting criminal intent remains challenging, assessment of medical impairment remains a viable target. One approach in which physicians could contribute their expertise includes training a subset of doctors to perform specialized medical evaluations as a prerequisite for gun ownership. Such a process is not unprecedented, as physicians currently have a role in protecting the public's safety through assessments for commercial drivers, pilots, and train operators. Certified physician examiners could conduct these evaluations with a focus on evaluating objective, skill-based metrics to limit potential evaluator bias. The results of the medical evaluation would then be considered by an existing regulatory body to determine if disqualifying criteria are present. This proposal provides a mechanism for trained physicians to meaningfully participate in addressing an alarming public health issue, while still working within existing legal frameworks.

A scalable, automated warm handoff from the emergency department to community sites offering continued medication for opioid use disorder: Lessons learned from the EMBED trial stakeholders

BACKGROUND

In order to streamline the emergency department (ED) referral process in a multi-network automated opioid treatment referral program, we performed a needs assessment of community providers for Medication for Opioid Use Disorder (MOUD) in the EMergency department-initiated BuprenorphinE for opioid use Disorder (EMBED) trial network.

METHODS

A needs assessment was conducted in two phases: (1) key stakeholder meetings and (2) a survey of community sites offering MOUD. Stakeholder meetings were conducted with five key stakeholder groups: 1) ED clinicians and staff, 2) community sites offering MOUD, 3) the investigative team, 4) health system IT staff, and 5) medical ethics experts. Meetings continued until each stakeholder group stated that their priorities and needs were understood. Major categories of needs were extracted pragmatically based on recurrence across stakeholder groups. Informed by needs expressed by IT and MOUD site stakeholders, nineteen MOUD sites were surveyed to better characterize information needs of community sites offering MOUD when receiving an ED referral.

RESULTS

Three major categories of needs for referral system were identified: 1) The system to be automated, flexible and allow multiple channels of referral, 2) Referral metrics are retrievable in a HIPAA compliant manner, 3) Patients are scheduled into community sites offering MOUD as urgently as possible. Of the MOUD sites surveyed, 68.4% (13/19) responded. Based on the responses, specific patient identifiers were required for most MOUD site referrals, and encrypted emails and EHR were the preferred methods of communication for the handoff. 53.8% (7/13) of the sites were able to accept patients within 3 days with only 1 site requiring >7 days.

CONCLUSION

These findings can inform IT solutions to address the discordant priorities of the ED (rapid and flexible referral process) and the community sites offering (referrals minimize variability and overbooking). To prevent drop-out in the referral cascade, our findings emphasize the need for increased availability and accessibility to MOUD on demand and protected communication channels between EDs and community providers of MOUD.

Efficacy of Extended-Release Naltrexone on HIV-Related and Drinking Outcomes Among HIV-Positive Patients: A Randomized-Controlled Trial

We sought to test the efficacy of extended-release naltrexone (XR-NTX) on HIV-related and drinking outcomes. From April 2011-February 2015, we conducted a 4-site randomized double-blind placebo controlled clinical trial involving 51 HIV-positive patients with heavy drinking and < 95% antiretroviral (ART) adherence. All participants received counseling. The primary outcome was proportion with ≥ 95% ART adherence. Secondary outcomes included HIV biomarkers, VACS Index score, and past 30-day heavy drinking days. Based on receipt of ≥ 5 injections, 23 participants were retained at 24 weeks. We did not detect an effect of XR-NTX on ART adherence (p = 0.38); undetectable HIV viral load (p = 0.26); CD4 cell count (p = 0.75) or VACS Index score (p = 0.70). XR-NTX was associated with fewer heavy drinking days (p = 0.03). While XR-NTX decreases heavy drinking days, we did not detect improvements in ART adherence or HIV outcomes. Strategies to improve retention in alcohol treatment and HIV-related outcomes among heavy drinking HIV-positive patients are needed.

Factors Affecting Resident Satisfaction in Continuity Clinic-a Systematic Review

PURPOSE

In recent years, with an increasing emphasis on time spent in ambulatory training, educators have focused attention on improving the residents' experience in continuity clinic. The authors sought to review the factors associated with physician trainee satisfaction with outpatient ambulatory training.

METHODS

A systematic literature review was conducted for all English language articles published between January 1980 and December 2016 in relevant databases, including Medline (medicine), CINAHL (nursing), PSYCHinfo (psychology), and the Cochrane Central Register of Controlled Clinical Trials. Search terms included internship and residency, satisfaction, quality of life, continuity of care, ambulatory care, and medical education. We included studies that directly addressed resident satisfaction in the ambulatory setting through interventions that we considered reproducible.

RESULTS

Three hundred fifty-seven studies were reviewed; 346 studies were removed based on exclusion criteria with 11 papers included in the final review. Seven studies emphasized aspects of organizational structure such as block schedules, working in teams, and impact on resident-patient continuity (continuity between resident provider and patient as viewed from the provider's perspective). Four studies emphasized the importance of a dedicated faculty for satisfaction. The heterogeneity of the studies precluded aggregate analysis.

CONCLUSIONS

Clinic structures that limit inpatient and outpatient conflict and enhance continuity, along with a dedicated outpatient faculty, are associated with greater resident satisfaction. Implications for further research are discussed.

Pharmacotherapy for Alcohol Use Disorder

Alcohol use disorder is a common, destructive, and undertreated disease. As understanding of alcohol use disorder has evolved, so has our ability to manage patients with pharmacotherapeutic agents in addition to nondrug therapy, including various counseling strategies. Providers now have a myriad of medications, both approved and not approved by the US Food and Drug Administration, to choose from and can personalize care based on treatment goals, comorbidities, drug interactions, and drug availability. This review explores these treatment options and offers the prescriber practical advice regarding when each option may or may not be appropriate for a specific patient.

Addressing discordant quantitative urine buprenorphine and norbuprenorphine levels: Case examples in opioid use disorder

INTRODUCTION

Urine adulteration is a concern among patients treated for opioid use disorder. Quantitative urine testing for buprenorphine (B) and norbuprenorphine (NB), and the appropriate interpretation of B and NB levels, can facilitate constructive conversations with patients that may lead to modifications in the treatment plan, and strengthening of the patient-provider relationship.

CASE SUMMARY

Three cases are presented in which discordant urine B and NB levels were recognized. Each patient was submerging buprenorphine/naloxone strips in their urine to mask ongoing illicit drug use. The authors used an approach to addressing intentional adulteration of urine samples that adheres to the principles of harm-reduction, the centrality of the patient-provider relationship, and the acknowledgment that ongoing illicit drug use and subsequent dishonesty about disclosure may be common among persons with substance use disorders. Each of the three patients ultimately endorsed diluting their urine, which allowed for strengthening of the patient-provider relationship and modifications to their treatment plans. Two of the three patients stabilized and achieved abstinence, while the third was eventually referred to a methadone treatment program.

CONCLUSION

Providers should routinely monitor B and NB levels, rather than qualitative screening alone, and discordant levels should elicit a timely conversation with the patient. The authors use of a nonjudgmental approach to address urine adulteration, including giving patients an opportunity to reflect on potential solutions, has been effective at helping patients and providers to reestablish a therapeutic alliance and maintain retention in treatment.

Objective Structured Clinical Examination-Based Teaching of the Musculoskeletal Examination

OBJECTIVES

Musculoskeletal complaints are the most common presenting illnesses in primary care settings, yet physicians often are underprepared to manage such complaints. We sought to create and evaluate an objective structured clinical examination (OSCE)-based musculoskeletal workshop designed to simultaneously educate medical students and internal medicine residents, enlisting volunteer medical students as standardized patients (SPs).

METHODS

The setting for the study was the Yale Primary Care Residency Program. A comprehensive OSCE-based musculoskeletal workshop series was created, consisting of standalone workshops with evidence-based interactive lectures followed by OSCE stations. At each station, residents are evaluated on physical examination skills, differential diagnosis, and therapeutic plan. We assessed the impact of exposure to the neck/back pain workshop using written knowledge and clinical skills tests (maximum score 32) among both residents and medical students 6 months after exposure.

RESULTS

A convenience sample of 13 residents exposed to the neck/back pain workshop was compared with 17 unexposed residents. Six months after exposure to the workshop, exposed residents, compared with unexposed residents, performed significantly better on a written knowledge test (score 8.6 vs 6.8, P = 0.005) and the clinical skills test (score 20.9 vs 17.1, P = 0.007). Similarly, medical student SPs performed significantly better on the clinical skills test (17.0 vs 12.0, P = 0.02), compared with the control students.

CONCLUSIONS

Our novel OSCE-based musculoskeletal workshop, which enlists medical students to serve as SPs, engendered sustainable improvements in knowledge and clinical skills among both residents and participating students, thereby offering an innovative approach to simultaneously meeting both undergraduate and graduate medical education needs.

Interpreting quantitative urine buprenorphine and norbuprenorphine levels in office-based clinical practice

BACKGROUND

Quantitative urine buprenorphine testing is used to monitor patients receiving buprenorphine for the treatment of opioid use disorder (OUD), however the interpretation of urine buprenorphine testing is complex. Currently, interpretation of quantitative buprenorphine testing is guided by data from drug assay development studies and forensic labs rather than clinical treatment cohorts.

METHODS

In this retrospective study, we describe the patterns of urine buprenorphine and norbuprenorphine levels in patients prescribed sublingual buprenorphine for OUD in an office-based addiction treatment clinic. Urine buprenorphine and norbuprenorphine levels were analyzed in patients who reported having adulterated their urine, patients clinically suspected of adulterating their urine, and patients without concern for urine adulteration. Finally, we tested the accuracy of urine buprenorphine, norbuprenorphine, and norbuprenorphine: buprenorphine ratio (Norbup:Bup) to identify adulterated urine samples.

RESULTS

Patients without suspicion for urine adulteration rarely provided specimens with buprenorphine >=1000ng/ml (4.4%), while the proportion provided by those who endorsed or were suspected of urine adulteration was higher (42.9%, 40.6%, respectively). Compared to patients without reported urine adulteration, specimens from patients who reported or were suspected of urine adulteration had significantly higher buprenorphine (p=0.0001) and lower norbuprenorphine (<0.0001) levels, and significantly lower Norbup:Bup ratios (p=0.04). Buprenorphine >=700ng/ml offered the best accuracy for discriminating between adulterated and non-adulterated specimens.

CONCLUSION

This study describes the patterns of urine buprenorphine and norbuprenorphine levels from patients with OUD receiving buprenorphine treatment in an office-based addiction treatment clinic. Parameters for identifying urine adulterated by submerging buprenorphine medication in the urine specimen are discussed.

The Addiction Recovery Clinic: A Novel, Primary-Care-Based Approach to Teaching Addiction Medicine

PROBLEM

Substance use is highly prevalent in the United States, but little time in the curriculum is devoted to training internal medicine residents in addiction medicine.

APPROACH

In 2014, the authors developed and launched the Addiction Recovery Clinic (ARC) to address this educational gap while also providing outpatient clinical services to patients with substance use disorders. The ARC is embedded within the residency primary care practice and is staffed by three to four internal medicine residents, two board-certified addiction medicine specialists, one chief resident, and one psychologist. Residents spend one half-day per week for four consecutive weeks at the ARC seeing new and returning patients. Services provided include pharmacological and behavioral treatments for opioid, alcohol, and other substance use disorders, with direct referral to local addiction treatment facilities as needed. Visit numbers, a patient satisfaction survey, and an end-of-rotation resident evaluation were used to assess the ARC.

OUTCOMES

From 2014 to 2015, 611 patient encounters occurred, representing 97 new patients. Sixty-one (63%) patients were seen for opioid use disorder. According to patient satisfaction surveys, 29 (of 31; 94%) patients reported that the ARC probably or definitely helped them to cope with their substance use. Twenty-eight residents completed the end-of-rotation evaluation; all rated the rotation highly.

NEXT STEPS

The ARC offers a unique primary-care-based approach to exposing internal medicine residents to the knowledge and skills necessary to diagnose, treat, and prevent unhealthy substance use. Future research will examine other clinical and educational outcomes.

Resident and Faculty Perceptions of Chart-Stimulated Recall

OBJECTIVES

Chart-stimulated recall (CSR) is a case-based interviewing technique advocated by the Accreditation Council for Graduate Medical Education as an assessment tool across a variety of clinical competencies, yet resident and faculty perceptions of this exercise have not been reported previously. The authors incorporated a CSR exercise into an internal medicine residency program and sought to assess the perceptions of residents and faculty participants.

METHODS

Faculty met weekly with night float residents at the end of their shift. The resident presented verbally while the faculty reviewed his or her written note. In the course of 3 years, 7 faculty and 73 residents participated. Participating residents completed an anonymous survey at the end of each academic year and faculty underwent a semistructured interview administered by the authors.

RESULTS

A total of 73% of resident respondents believed that CSR was a valuable component of the night float rotation and should be continued. Faculty believed that the exercise allowed time for focused teaching of the night team, who otherwise received limited formal instruction. The most common critique of the sessions was the timing, because the residents often reported feeling too tired to engage actively in the sessions.

CONCLUSIONS

CSR was easy to implement, received well, and educationally valued by both residents and faculty. Participants viewed the exercise as useful for both teaching and formative assessment.

Instruments to assess patient-reported safety, efficacy, or misuse of current opioid therapy for chronic pain: a systematic review

The purpose of this systematic review was to summarize and critically appraise research developing or validating instruments to assess patient-reported safety, efficacy, and/or misuse in ongoing opioid therapy for chronic pain. Our search included the following datasets: OvidSP MEDLINE (1946-August 2012), OvidSP PsycINFO (1967-August 2012), Elsevier Scopus (1947-August 2012), OvidSP HaPI (1985-August 2012), and EBSCO CINAHL (1981-August 2012). Eligible studies were published in English and pertained to adult, nonsurgical/interventional populations. Two authors independently assessed inclusion criteria. Each study was evaluated by 2 authors to assess the sources and content of items, types of psychometric tests, their results, and quality of diagnostic accuracy testing, when applicable. Of 1874 citations found in the initial search, we identified 14 studies meeting our inclusion criteria, describing 9 different instruments. Individual items were derived from surveys of content experts, literature reviews, and adapted non-patient-reported items. Misuse-related items were most prevalent (60/144; 42%), followed by safety (47/144; 33%), with efficacy having the fewest items (17/144; 12%). The studies employed a wide variety of psychometric tests, with most demonstrating statistical significance, but several potential sources of bias and generalizability limitations were identified. Lack of testing in clinical practice limited assessment of feasibility. The dearth of safety and efficacy items and lack of testing in clinical practice demonstrates areas for further research.

Physician detection of unhealthy substance use on inpatient teaching and hospitalist medical services

BACKGROUND

Screening, brief intervention, and referral to treatment for substance use depends on reliable identification. The goal of this study was to determine the rate of detection of unhealthy substance use by physicians on teaching and nonteaching medical services at a community teaching hospital.

METHODS

This cross-sectional study was conducted from February to June 2009. All new medicine admissions to the Teaching Service or the nonteaching Hospitalist Service were assessed for unhealthy substance use using the Alcohol Use Disorders Identification Test-Consumption (AUDIT-C) and Drug Abuse Screening Test (DAST). All patients identified with substance use completed the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST). Medical record review was also performed to assess physician documentation.

RESULTS

Of 442 eligible patients, 414 consented to participate. Patients on the Teaching Service were more likely to be male, younger, unmarried, non-white, uninsured or receiving publicly funded insurance, and current smokers (p < .01 for all comparisons). Overall, the detection rate for unhealthy substance use was 64.3% (63 of 98 confirmed cases), with service-specific rates of 73.4% for the Teaching Service, compared with 47.1% for the Hospitalist Service (p = .011). ICD-9 coding accounted for 53.1% of identified cases on the Teaching Service and 14.7% of identified cases on the Hospitalist Service (p < .001). Assignment to the Hospitalist Service, being married, and isolated unhealthy drug use were independently associated with decreased physician detection rates.

CONCLUSIONS

Our study suggests that unhealthy substance use is more likely to be detected on a Teaching Service than on a Hospitalist Service.

Prevalence of unhealthy substance use on teaching and hospitalist medical services: implications for education

The prevalence of unhealthy substance use (USU) among medical inpatients can vary, and prior research has not characterized the prevalence of USU among patients cared for by a teaching service (TS) and a nonteaching hospitalist service (NTHS). The objective of this study was to compare the prevalence of USU among patients cared for by a TS and an NTHS. We conducted a cross-sectional study from February to June 2009 at a community teaching hospital. Within 24 hours of admission, all eligible internal medicine admissions to the TS or NTHS were screened for USU, using the Alcohol Use Disorders Identification Test-Consumption and Drug Abuse Screening Test. Patients screening positive then underwent a diagnostic interview and blinded chart review to increase case finding and to assess whether each patient's admission was related to USU. There were 414 eligible and consenting patients out of 656 patients identified. Patients on the TS were younger and more likely to be current smokers, male, unmarried, non-white, and unemployed (p<.01 for all comparisons). TS patients were more likely to have evidence of USU (29.2% vs. 12.3%; p<.01). Among all admissions to the TS, 22.2% were deemed to be probably or possibly due to USU, as compared with only 3.7% of admissions to the NTHS (p<.01). Medical TSs care for a greater share of patients with USU as compared with an NTHS. These data highlight the need for expanded medical resident training in the diagnosis and management of USU.

Interaction of the ruthenium red cation with nucleic acid double helices

The hexapositive complex cation ruthenium red very effectively stabilizes DNA and RNA double helices against thermal denaturation. In the presence of nucleic acid helices, this symmetric cation acquires an extrinsic CD spectrum near the wavelength of the dye's maximum absorbance. Competition experiments with single-stranded polyd(T) show this induced CD to be the result of selective binding to helical sites. The preferential affinity of ruthenium red for double helical binding sites is so great that it brings about biphasic absorbance- temperature profiles of polyd(A-T) at low [cation]: [polynucleotide phosphate]. The visible CD signal and fraction of helix melting at the upper transition increases with ruthenium red concentration until approximate charge neutrality is reached. These interactions, which have been studied in detail with the poly(U-U) helix as well as polyd(A-T), are likely largely electrostatic, since sufficient [NaCl] eliminates the bipliasic melting of polyd(A-T), renders the ultraviolet absorbance of poly (U) insensitive to ruthenium red, and abolishes the induced CD effects. The bipliasic melting of polyd(A-T) at intermediate [dye] is attributed to saturation of remaining double helical segments by cation migration from newly melted regions- Furthermore, virtually no change was observed in the induced CD upon melting through the first transition, whereas the effect is destroyed upon inciting through the second transition. A quantitative treatment of the data is used to obtain binding site size and association constant for the complex. The induced effect may prove useful in the exploration of exposed nucleic acid helical structure in such complex particles as nucleosomes or ribosomes.

Temperature dependent modulation of lobster neuromuscular properties by serotonin

In cold-blooded species the efficacy of neuromuscular function depends both on the thermal environmental of the animal's habitat and on the concentrations of modulatory hormones circulating within the animal's body. The goal of this study is to examine how temperature variation within an ecologically relevant range affects neuromuscular function and its modulation by the neurohormone serotonin (5-HT) in Homarus americanus, a lobster species that inhabits a broad thermal range in the wild. The synaptic strength of the excitatory and inhibitory motoneurons innervating the lobster dactyl opener muscle depends on temperature, with the strongest neurally evoked muscle movements being elicited at cold (<5 degrees C) temperatures. However, whereas neurally evoked contractions can be elicited over the entire temperature range from 2 to >20 degrees C, neurally evoked relaxations of resting muscle tension are effective only at colder temperatures at which the inhibitory junction potentials are hyperpolarizing in polarity. 5-HT has two effects on inhibitory synaptic signals: it potentiates their amplitude and also shifts the temperature at which they reverse polarity by approximately +7 degrees C. Thus 5-HT both potentiates neurally evoked relaxations of the muscle and increases the temperature range over which neurally evoked muscle relaxations can be elicited. Neurally evoked contractions are maximally potentiated by 5-HT at warm (18 degrees C) temperatures; however, 5-HT enhances excitatory junction potentials in a temperature-independent manner. Finally, 5-HT strongly increases resting muscle tension at the coldest extent of the temperature range tested (2 degrees C) but is ineffective at 22 degrees C. These data demonstrate that 5-HT elicits several temperature-dependent physiological changes in the passive and active responses of muscle to neural input. The overall effect of 5-HT is to increase the temperature range over which neurally evoked motor movements can be elicited in this neuromuscular system.