Cervical and trigeminal afferents innervate neighboring cranial territories, and their convergence on upper cervical dorsal horn neurons provides a potential substrate for pain referral in primary headache syndromes. Lamina I neurons are central to this mechanism as they relay convergent nociceptive input to supraspinal pain centers. Unfortunately, little is known about the interactions between trigeminal and cervical afferents supplying lamina I neurons. Here we used rats of both sexes to show that cervical and trigeminal afferents interact via presynaptic inhibition, where monosynaptic inputs to lamina I neurons undergo unidirectional as well as reciprocal presynaptic control. This means that afferent-driven presynaptic inhibition shapes the way trigeminal and cervical Aδ- and C-fiber input reaches lamina I projection and local-circuit neurons. We propose that this inhibition provides a feedforward control of excitatory drive to lamina I neurons that regulates their convergent and cervical- or trigeminal...

Metacognition describes the process of monitoring one’s own mental states, often for the purpose of cognitive control. Previous research has investigated how metacognitive signals are generated (metacognitive monitoring), for example when people (both f/m) judge their confidence in their decisions and memories. Research has also investigated how metacognitive signals are used to influence behavior (metacognitive control), for example setting a reminder (i.e. cognitive offloading ) for something you are not confident you will remember. However, the mapping between metacognitive monitoring and metacognitive control needs further study on a neural level. We used fMRI to investigate a delayed-intentions task with a reminder element, allowing human participants to use their metacognitive insight to engage metacognitive control. Using multivariate pattern analysis, we found that we could separately decode both monitoring and control, and, to a lesser extent, cross-classify between them. Therefore, brain patterns...

Traumatic spinal cord injury (SCI) above the major spinal sympathetic outflow (T6 level) disinhibits sympathetic neurons from supraspinal control, causing systems-wide ‘dysautonomia’. We recently showed that remarkable structural remodeling and plasticity occurs within spinal sympathetic circuitry, creating abnormal sympathetic reflexes that exacerbate dysautonomia over time. As an example, thoracic VGlut2+ spinal interneurons (SpINs) become structurally and functionally integrated with neurons that comprise the spinal-splenic sympathetic network and immunological dysfunction becomes progressively worse after SCI. To test whether the onset and progression of SCI-induced sympathetic plasticity is neuron activity-dependent, we selectively inhibited (or excited) thoracic VGlut2+ interneurons using chemogenetics. New data show that silencing VGlut2+ interneurons in female and male mice with a T3 SCI, using hM4Di-designer receptors exclusively activated by designer drugs (Gi DREADDs), blocks structural plastici...

Dynamic functional connectivity within brain circuits requires coordination of intercellular signaling and intracellular signal transduction. Critical roles for cAMP-dependent Protein Kinase A (PKA) signaling are well established in the Drosophila Mushroom Body (MB) learning and memory circuitry, but local PKA activity within this well-mapped neuronal network is uncharacterized. Here, we use an in vivo PKA activity sensor (PKA-SPARK) to test spatiotemporal regulatory requirements in the MB axon lobes. We find immature animals have little detectable PKA activity, whereas post-critical period adults show high field-selective activation primarily in just 3/16 defined output regions. In addition to the age-dependent PKA activity in distinct α’/β’ lobe nodes, females show sex-dependent elevation compared to males in these same restricted regions. Loss of neural cell body Fragile X Mental Retardation Protein (FMRP) and Rugose (human Neurobeachin) suppresses localized PKA activity, whereas over-expression of MB l...

Current methods to isolate synaptic vesicles (SVs), the organellar quanta of synaptic transmission, require highly specialized materials and up to 24 hours. These technical obstacles have thus far limited the study of SVs in models of synaptic function and pathophysiology. Here, we describe techniques for the rapid isolation of SVs by immunoprecipitation with widely available antibodies conjugated to magnetic beads. We report that the inexpensive rho1D4 monoclonal antibody binds SVs and show that elution with the 1D4 peptide yields native vesicles that are ≥ 10-fold purer than those obtained with classical techniques. These methods substantially widen the accessibility of SVs, enabling their purification in 60-90 minutes for downstream analyses including mass spectrometry and cryo-electron microscopy. Immunopurified SV preparations from mouse brain contained apolipoprotein E (ApoE), the low-density lipoprotein (LDL) receptor Lrp1, and enzymes involved in lipid metabolism, suggesting that SVs may play direc...

The high sensitivity of night vision requires that rod photoreceptors reliably and reproducibly signal the absorption of single photons, a process that depends on tight regulation of intracellular cGMP concentration through the phototransduction cascade. Here in the mouse (Mus musculus), we studied a single-site D167A mutation of the gene for the α subunit of rod photoreceptor phosphodiesterase (PDEA), made with the aim of removing a noncatalytic binding site for cGMP. This mutation unexpectedly eliminated nearly all PDEA expression and reduced expression of the β subunit (PDEB) to ∼5%-10% of WT. The remaining PDE had nearly normal specific activity; degeneration was slow, with 50%-60% of rods remaining after 6 months. Responses were larger and more sensitive than normal but slower in rise and decay, probably from slower dark turnover of cGMP. Remarkably, responses became much less reproducible than WT, with response variance increasing for amplitude by over 10-fold, and for latency and time-to-peak by >10...

Malfunctioning synaptic plasticity is one of the major mechanisms contributing to the development of chronic pain. We studied spike-timing dependent depression (tLTD) in the anterior cingulate cortex (ACC) of male mice, a brain region involved in processing emotional aspects of pain. tLTD onto layer 5 pyramidal neurons depended on postsynaptic calcium-influx through GluN2B-containing NMDARs and retrograde signaling via nitric oxide to reduce presynaptic release probability. After chronic constriction injury of the sciatic nerve, a model for neuropathic pain, tLTD was rapidly impaired; and this phenotype persisted even beyond the time of recovery from mechanical sensitization. Exclusion of GluN2B-containing NMDARs from the postsynaptic site specifically at projections from the anterior thalamus to the ACC caused the tLTD phenotype, whereas signaling downstream of nitric oxide synthesis remained intact. Thus, transient neuropathic pain can leave a permanent trace manifested in the disturbance of synaptic pla...

Theta oscillations are key brain rhythm involved in memory formation, sensorimotor integration, and control of locomotion and behavioral states. Generation and spatiotemporal synchronization of theta oscillations rely on interactions between brain nuclei forming a large neural network, which includes pontine nucleus incertus (NI). Here we identified distinct populations of NI neurons, based on the relationship of their firing to hippocampal waves, with a special focus on theta oscillations, and the direction and type of interaction with the medial septum (MS) in male, urethane-anesthetized rats. By recording NI neuronal firing and hippocampal LFP, we described NI neurons that fire action potentials in a theta phase-independent or theta phase-locked and delta wave-independent or delta wave-locked manner. Among hippocampal activity-independent NI neurons, irregular, slow-firing, and regular, fast-firing cells were observed, while hippocampal oscillation-/wave-locked NI neurons were of a bursting or nonbursti...

Individuals with chronic pain often experience depression, resulting in greater disability and a worse prognosis than either condition alone ([Goesling et al., 2013][1]). The prevalence of depression among individuals experiencing neuropathic pain, one type of chronic pain caused by injury of the