The functional role of nicotinic acetylcholine receptors (nAChRs) in the ventral lateral geniculate nucleus (LGNv) was examined in chick brain slices. Whole-cell patch-clamp recordings of neurons in the LGNv revealed the presence of bicuculline-resistant spontaneous postsynaptic currents (PSCs), which were subsequently blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an AMPA receptor antagonist. Carbachol and other nicotinic agonists produced marked increases in the frequency of the glutamatergic spontaneous PSCs in the presence of tetrodotoxin, whereas they had little or no effect on current amplitude. The nicotinic receptor antagonist dihydro-beta-erythroidine (DHbetaE) blocked the carbachol-induced enhancement of spontaneous glutamatergic PSCs. alpha-bungarotoxin (alpha-BgTx) selectively blocked the nAChR-mediated enhancement of spontaneous glutamatergic PSCs but did not prevent nAChR-mediated enhancement of spontaneous GABAergic PSCs in the LGNv. Methyllycaconitine and strychnine, other blockers of nAChRs containing the alpha7 subunit, failed to inhibit carbachol's increase of spontaneous glutamatergic and GABAergic PSCs. These results demonstrate that the LGNv neurons receive both glutamatergic and GABAergic inputs and that the release of these transmitters can be modulated by different presynaptic nAChRs. Thus, the regulation of synaptic efficacy in the brain by presynaptic nAChRs can be complex, involving multiple neurotransmitters acting on the same neuron.

The role of voltage-dependent calcium channels (VDCCs) in the nicotinic acetylcholine receptor (nAChR)-mediated enhancement of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) was investigated in chick brain slices. Whole cell recordings of neurons in the lateral spiriform (SpL) and ventral lateral geniculate (LGNv) nuclei showed that cadmium chloride (CdCl2) blocked the carbachol-induced increase of spontaneous GABAergic IPSCs, indicating that VDCCs might be involved. To conclusively show a role for VDCCs, the presynaptic effect of carbachol on SpL and LGNv neurons was examined in the presence of selective blockers of VDCC subtypes. omega-Conotoxin GVIA, a selective antagonist of N-type channels, significantly reduced the nAChR-mediated enhancement of gamma-aminobutyric acid (GABA) release in the SpL by 78% compared with control responses. Nifedipine, an L-type channel blocker, and omega-Agatoxin-TK, a P/Q-type channel blocker, did not inhibit the enhancement of GABAergic IPSCs. In the LGNv, omega-Conotoxin GVIA also significantly reduced the nAChR-mediated enhancement of GABA release by 71% from control values. Although omega-Agatoxin-TK did not block the nicotinic enhancement, L-type channel blockers showed complex effects on the nAChR-mediated enhancement. These results indicate that the nAChR-mediated enhancement of spontaneous GABAergic IPSCs requires activation of N-type channels in both the SpL and LGNv.

Objectives: Previous studies have not evaluated the utility of obtaining chest radiographs (CXR) in patients with acute asthma exacerbation reporting chest pain. The aims of this study were to evaluate the symptom of chest pain as a predictor for clinicians obtaining a CXR in these patients and to evaluate chest pain as a predictor of a positive CXR finding.Methods: This was a retrospective chart review of patients, ages 2 to 18 years, presenting for acute asthma exacerbation to the emergency department from August 1, 2014, to March 31, 2016. Data collected included demographics, clinical data, provider type, and CXR results. Chest radiographs were classified as positive if they showed evidence of pneumonia, pneumothorax, or pneumomediastinum. Multivariate logistic regression models were developed with dependent variables of "obtaining a CXR" and "a positive CXR finding."Results: Seven hundred ninety-three subjects were included in the study.Two hundred thirty-one (29.1%) reported chest pain. Chest radiographs were obtained in 184 patients (23.2%). Of those, 74 patients (40.2%) had chest pain and 21 (11.4%) had a positive CXR. Providers were more likely to obtain CXRs in patients who reported chest pain (odds ratio = 2.2 [95% confidence interval = 1.5-3.2]). Patients reporting chest pain were more likely to have a positive CXR although this difference was not statistically significant (odds ratio = 2.0 [95% confidence interval = 0.7-5.6]).Conclusions: Providers are more likely to obtain CXRs in asthmatic patients complaining of chest pain; however, these CXRs infrequently yield positive findings. This further supports limiting the use of chest radiography in patients with acute asthma exacerbation.