Although sensitization-related changes in the neural circuitry of withdrawal reflexes in Aplysia are well studied, relatively few studies address the organization of the modulatory components of sensitization. In particular, it is not known whether individual modulatory loci can simultaneously influence multiple reflex circuits. There is, however, evidence that a single modulatory transmitter, serotonin, plays a pivotal role in facilitating different reflex circuits during sensitization. Furthermore, it is known that activation of a pair of serotonergic neurons, the CB1s, produces heterosynaptic facilitation of the sensorimotor connections of one of these reflex circuits. These data together raise the possibility that the CB1s may produce sensitizing changes in the neural elements of multiple reflex systems simultaneously. In the present study, we utilized immunocytochemistry and intracellular labeling to obtain anatomical evidence of CB1's possible role in modulating multiple reflex circuits. We found that two distinct neurons satisfy previously published physiological criteria for CB1. One of these, CB1, is immunoreactive to serotonin. The second cell, here named CB2, has a different neuroanatomy and is not serotonin immunoreactive. Focusing on CB1, we found (1) profuse fine processes given off by its axons in the posterior neuropil of the cerebral ganglion, (2) extensive branching and fine processes in the pleural ganglion, and (3) a branch of CB1 that projects into the pedal ganglion. These three observations are consistent with the hypothesis that, in addition to its already established role in modulating the siphon withdrawal circuit, CB1 may also modulate synaptic connections between (1) the sensory and motor neurons of the tentacle withdrawal reflex (2) the sensory neurons and interneurons of the tail and tail-elicited siphon withdrawal reflex, and (3) the sensory and motor neurons of the tail withdrawal reflex. These observations support further physiological investigations of a possible global role of CB1 in modulating the tail and tentacle withdrawal reflexes.

In the Medicare population, radiologists interpret most lower extremity joint MRI examinations. Compared with nonradiologists, radiologists disproportionately provide services on weekends, in the highest acuity settings, and on the most clinically complex patients. To promote patient access and minimize disparities, future pay-for-performance metrics should consider temporal, acuity, and complexity parameters.

BACKGROUND AND PURPOSE: Although most neuroimaging examinations are interpreted by radiologists, many nonradiologists provide interpretation services. We studied day of the week, site of service, and patient complexity differences for common Medicare MR neuroimaging examinations interpreted by radiologists versus nonradiologists. MATERIALS AND METHODS: Using carrier claims files for a 5% sample of Medicare beneficiaries from 2012 to 2014, we identified all claims for brain and lumbar spine MR imaging examinations. Services were categorized by physician specialty, day of the week, and the site of service. Patient complexity was calculated using Charlson Comorbidity Indices. The 2 was performed to test statistical significance. RESULTS: A provider specialty could be identified for 568,423 brain and lumbar spine MR imaging examinations. Of weekday examinations, radiologists interpreted 475,288 (92.3%), and nonradiologists, 39,510 (7.7%). Of weekend examinations, radiologists interpreted 52,028 (97.0%) and nonradiologists 1597 (3.0%). Radiologists interpreted 145,904 (98.7%) examinations in the inpatient hospital and emergency department settings versus 1882 (1.3%) by nonradiologists. Of all examinations, 44,547 of those interpreted by radiologists (8.4%) were on the most clinically complex patients versus 2139 (5.2%) for nonradiologists. All interspecialty differences for day of the week, the site of service, and patient complexity were statistically significant (P Ͻ .001). CONCLUSIONS: Although radiologists interpret most common MR neuroimaging examinations for Medicare beneficiaries, in contrast to nonradiologists, they disproportionately render those services on weekends, in higher acuity sites, and on more complex patients. To optimize access and minimize disparities in necessary neuroimaging, quality metrics should consider such service characteristics.