Fentanyl and morphine, but not remifentanil, inhibit acetylcholine release in pontine regions modulating arousal

BACKGROUND

Opioids inhibit the rapid eye movement (REM) phase of sleep and decrease acetylcholine (ACh) release in medial pontine reticular formation (mPRF) regions contributing to REM sleep generation. It is not known whether opioids decrease ACh release by acting on cholinergic cell bodies or on cholinergic axon terminals. This study used in vivo microdialysis to test the hypothesis that opioids decrease ACh levels at cholinergic neurons in the laterodorsal tegmental nuclei (LDT) and LDT axon terminals in the mPRF.

METHODS

Nine male cats were anesthetized with halothane, and ACh levels within the mPRF or LDT were assayed using microdialysis and high-pressure liquid chromatography (HPLC). ACh levels were analyzed in response to dialysis of the mPRF and LDT with Ringer's solution (control), followed by dialysis with Ringer's solution containing morphine sulfate (MSO4) or naloxone. ACh in the mPRF also was measured during either dialysis delivery or intravenous infusion of remifentanil and during dialysis delivery of fentanyl.

RESULTS

Compared with dialysis of Ringer's solution, microdialysis with MSO4 decreased ACh by 23% in the mPRF and by 30% in the LDT. This significant decrease in ACh was antagonized by naloxone. MSO4 and fentanyl each caused a dose-dependent decrease in mPRF ACh when delivered by dialysis. Remifentanil delivered by continuous intravenous infusion or by dialysis into the mPRF did not alter mPRF ACh.

CONCLUSIONS

Morphine inhibits ACh at the cholinergic cell body region (LDT) and the terminal field in the mPRF. ACh in the mPRF was not altered by remifentanil and was significantly decreased by fentanyl. Thus, MSO4 and fentanyl disrupt cholinergic neurotransmission in the LDT-mPRF network known to modulate REM sleep and cortical electroencephalographic activation. These data are consistent with the possibility that inhibition of pontine cholinergic neurotransmission contributes to arousal state disruption by opioids.

CT Perfusion in Acute Lacunar Stroke: Detection Capabilities Based on Infarct Location

BACKGROUND AND PURPOSE

Recent studies demonstrated superiority of CTP to NCCT/CTA at detecting lacunar infarcts. This study aimed to assess CTP's capability to identify lacunae in different intracranial regions.

MATERIALS AND METHODS

Over 5.5 years, 1085 CTP examinations were retrospectively reviewed in patients with acute stroke symptoms with CTP within 12 hours and MRI within 7 days of symptom onset. Patients had infarcts ≤2 cm or no acute infarct on DWI; patients with concomitant infarcts >2 cm on DWI were excluded. CTP postprocessing was automated by a delay-corrected algorithm. Three blinded reviewers were given patient NIHSS scores and symptoms; infarcts were recorded based on NCCT/CTA, CTP (CBF, CBV, MTT, and TTP), and DWI.

RESULTS

One hundred thirteen patients met inclusion criteria (53.1% female). On DWI, lacunar infarcts were present in 37 of 113 (32.7%), and absent in 76 of 113 (67.3%). On CTP, lacunar infarcts typically appeared as abnormalities larger than infarct size on DWI. Interobserver κ for CTP ranged from 0.38 (CBF) (P < .0001) to 0.66 (TTP) (P < .0001); interobserver κ for DWI was 0.88 (P < 0.0001). In all intracranial regions, sensitivity of CTP ranged from 18.9% (CBV) to 48.7% (TTP); specificity ranged from 97.4% (CBF and TTP) to 98.7% (CBV and MTT). CTP's sensitivity was highest in the subcortical white matter with or without cortical involvement (21.7%-65.2%) followed by periventricular white matter (12.5%-37.5%); sensitivity in the thalami or basal ganglia was 0%.

CONCLUSIONS

CTP has low sensitivity and high specificity in identifying lacunar infarcts. Sensitivity is highest in the subcortical white matter with or without cortical involvement, but limited in the basal ganglia and thalami.

Tissue-specific expression and circulating concentrations of nesfatin-1 in domestic animals

Nesfatin-1 is a naturally occurring 82-amino acid protein encoded in the precursor nucleobindin-2 (NUCB2) and has been implicated in multiple physiological functions, including food intake and blood glucose regulation. This study aimed to characterize nesfatin-1 in domestic species, especially cats (Felis catus), dogs (Canis lupus familiaris), and pigs (Sus scrofa). Our in silico analysis demonstrated that the NUCB2/nesfatin-1 amino acid sequence, especially the bioactive core region of the peptide, is very highly conserved (more than 90% identity) in domestic animals. Expression of mRNAs encoding NUCB2/nesfatin-1 was detected in the cat, dog, and pig stomach and pancreas. Immunohistochemistry revealed the presence of nesfatin-1 in the gastric mucosa of the stomach of dogs, cats, and pigs, and in the pancreatic islet β-cells of dogs and pigs. No nesfatin-1 immunoreactivity was found in the cat pancreas. Nesfatin-1 was detected in the serum of dog, cat, pig, bison, cow, horse, sheep, and chicken. Circulating nesfatin-1 in male and female dogs remained unchanged at 60 min after glucose administration, suggesting a lack of meal responsiveness in nesfatin-1 secretion in this species. The presence of nesfatin-1 in the gastric and endocrine pancreatic tissues suggests possible roles for this peptide in the metabolism of domestic animals. Future research should focus on elucidating the species-specific functions and mechanisms of action of nesfatin-1 in health and disease of domestic animals.

Effect of pentaphasic pulse sequence as an impedance sensor on standard electrocardiographic recordings

Two advances in cardiac pacing have resulted in an internal conflict in some pacemakers. One is the development of a standard lead physiological sensor and the other is protection from electromagnetic interference (EMI). One popular type of standard lead sensor uses sub-threshold pulses to measure intracardiac and intrathoracic impedance changes, i.e., minute ventilation. Recent clinical observations and extensive in vitro testing have verified that digital cellular phones can be troublesome. Large feedthrough capacitors (FCs), effective in blocking the EMI, will preclude sensing of the standard impedance-based signals. A variety of pulse configurations were studied that might be effective for a sensor-based impedance signal while allowing the pacemaker to continue to use large Fcs protecting them from environmental EMI. In comparison to both monophasic and biphasic pulse sequences, a pentaphasic pulse sequence was effective as an impedance sensor, still allows large FCs to function as an effective filter for environmental EMI, and would not produce artifacts on surface ECG.

Evaluation of Blood Parameters Alteration Following Low-dose Radiation Induced by Myocardial Perfusion Imaging

INTRODUCTION

With increasing the usage of myocardial perfusion imaging (MPI) for the diagnosis of ischemic heart disease, we aimed to evaluate the side effects of low-dose radiation induced by this technique on blood elements, especially proteins and liver function factors.

MATERIAL AND METHODS

40 eligible patients (Mean age: 54.62±10.35, 22 female and 18 male), who had referred to the nuclear medicine department for MPI from May till August 2014, were enrolled in the study. A blood sample was taken from each patient just before and 24 hours after the injection of 740Mbq of Tecnetium-99m Methoxy isobutyl isonitrile (99mTc-MIBI) in the rest phase of the MPI in a reference medical laboratory; blood tests included total protein (TP), albumin (Alb), globulin (Glo), aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), direct bilirubin (D.Bili), total bilirubin (T.Bili), serum iron (SI), total iron bounding capacity (TIBC), Albumin globulin ratioA/G ratio), and complete blood count (CBC).

RESULTS

Injection of 740Mbq99mTc-MIBI caused a significant increase in serum levels of AST (p= 0.001), ALT (p= 0.001), SI (p= 0.030), TIBC (p= 0.003) and A/G Ratio (p= 0.020). However, following radiotracer injection, a significant decrease was noted in the serum levels of TP (p= 0.002), Alb (p= 0.014), Glo(p= 0.002), ALP (p= 0.001), D.Bili (p= 0.003) and T.Bili (p= 0.000).

CONCLUSION

Due to increased usage of MPI, our data highlights the importance of monitoring the clinical and paraclinical effects of the procedure on vital organs and physiological pathways to reduce their adverse effects.