Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs

PURPOSE: The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures. METHODS: Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments. Two to 4 weeks after initial recordings, an intraocular injection of tetrodotoxin (TTX) was given and the mfERG was rerecorded as described above. Data were analyzed using mixed models in SAS statistical software. RESULTS: Propofol significantly decreases the conventional and global-flash amplitudes over time. The only significant effect of isoflurane is a decrease in the global-flash amplitudes. At 15 minutes after TTX injection several of the mfERG amplitudes are significantly decreased. There is a linear correlation between the conventional P1 and the global-flash DR mfERG-amplitude (R(2) = 0.82, slope = 0.72, P < 0.0001). There is no significant difference between the 3-minute and the prolonged mfERG recordings for conventional amplitudes and the global-flash direct response. The global flash–induced component significantly decreases with prolonged mfERG recordings. CONCLUSIONS: A 3-minute mfERG recording and a single stimulation protocol is sufficient in anesthetized pigs. Recordings should be obtained immediately after the induction of anesthesia. The effect of TTX is significant 15 minutes after injection, but is contaminated by the effect of anesthesia 90 minutes after injection. Therefore, the quality of mfERG recordings can be further improved by determining the necessary time-of-delay from intraocular injection of a drug to full effect. TRANSLATIONAL RELEVANCE: General anesthesia is a possible source of error in mfERG recordings. Therefore, it is important to investigate the translational relevance of the results to mfERG recordings in children in general anesthesia

Retinal layer segmentation in rodent OCT images: Local intensity profiles & fully convolutional neural networks

[EN] Background and Objective: Optical coherence tomography (OCT) is a useful technique to monitor retinal layer state both in humans and animal models. Automated OCT analysis in rats is of great relevance to study possible toxic effect of drugs and other treatments before human trials. In this paper, two different approaches to detect the most significant retinal layers in a rat OCT image are presented. Methods: One approach is based on a combination of local horizontal intensity profiles along with a new proposed variant of watershed transformation and the other is built upon an encoder-decoder convolutional network architecture. Results: After a wide validation, an averaged absolute distance error of 3.77 +/- 2.59 and 1.90 +/- 0.91 mu m is achieved by both approaches, respectively, on a batch of the rat OCT database. After a second test of the deep-learning-based method using an unseen batch of the database, an averaged absolute distance error of 2.67 +/- 1.25 mu m is obtained. The rat OCT database used in this paper is made publicly available to facilitate further comparisons. Conclusions: Based on the obtained results, it was demonstrated the competitiveness of the first approach since outperforms the commercial Insight image segmentation software (Phoenix Research Labs) as well as its utility to generate labelled images for validation purposes speeding significantly up the ground truth generation process. Regarding the second approach, the deep-learning-based method improves the results achieved by the more conventional method and also by other state-of-the-art techniques. In addition, it was verified that the results of the proposed network can be generalized to new rat OCT images.Animal experiment permission was granted by the Danish Animal Experimentation Council (license number: 2017-15-020101213). We gratefully acknowledge the support of NVIDIA Corporation with the donation of the Titan V GPU used for this research. This work has received funding from Horizon 2020, the European Union's Framework Programme for Research and Innovation, under grant agreement No. 732613 (GALAHAD Project), the Spanish Ministry of Economy and Competitiveness through project DPI2016-77869 and GVA through project PROMETEO/2019/109.Morales, S.; Colomer, A.; Mossi García, JM.; Del Amor, R.; Woldbye, D.; Klemp, K.; Larsen, M.... (2021). Retinal layer segmentation in rodent OCT images: Local intensity profiles & fully convolutional neural networks. Computer Methods and Programs in Biomedicine. 198:1-14. https://doi.org/10.1016/j.cmpb.2020.105788S11419

Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs

Purpose: The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures. Methods: Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments. Two to 4 weeks after initial recordings, an intraocular injection of tetrodotoxin (TTX) was given and the mfERG was rerecorded as described above. Data were analyzed using mixed models in SAS statistical software. Results: Propofol significantly decreases the conventional and global-flash amplitudes over time. The only significant effect of isoflurane is a decrease in the globalflash amplitudes. At 15 minutes after TTX injection several of the mfERG amplitudes are significantly decreased. There is a linear correlation between the conventional P1 and the global-flash DR mfERG-amplitude (R 2 ¼ 0.82, slope ¼ 0.72, P , 0.0001). There is no significant difference between the 3-minute and the prolonged mfERG recordings for conventional amplitudes and the global-flash direct response. The global flash-induced component significantly decreases with prolonged mfERG recordings. Conclusions: A 3-minute mfERG recording and a single stimulation protocol is sufficient in anesthetized pigs. Recordings should be obtained immediately after the induction of anesthesia. The effect of TTX is significant 15 minutes after injection, but is contaminated by the effect of anesthesia 90 minutes after injection. Therefore, the quality of mfERG recordings can be further improved by determining the necessary time-of-delay from intraocular injection of a drug to full effect. Translational Relevance: General anesthesia is a possible source of error in mfERG recordings. Therefore, it is important to investigate the translational relevance of the results to mfERG recordings in children in general anesthesia

Neuropeptide Y Attenuates Naloxone-Precipitated Morphine Withdrawal via Y5-like Receptors

The effects of intracerebroventricular injection of neuropeptide Y (NPY) and various NPY-related peptides were studied on naloxone-precipitated withdrawal from morphine in rats. The withdrawal reaction was assessed using an overall motor score, including jumping, wet dog shakes and other motor-related signs as well as a nonmotor score. At doses of 3, 6 or 12 nmol, NPY strongly and dose-dependently reduced the motor score. A less prominent inhibitory effect was revealed on the nonmotor score. At 6 nmol, [Leu31,Pro34]-NPY, NPY 3-36, peptide YY and human pancreatic polypeptide all significantly attenuated the motor score, whereas NPY 13-36 was without effect. This pharmacological profile suggests that the antiwith-drawal effect of NPY is mediated via the recently cloned Y5 receptor. Our data are consistent with a potential role for NPY and Y5-like receptors in basic mechanisms and as a therapeu-tic target in opioid dependence and withdrawal. The study of opioid dependence holds the promise of lead-ing to pharmacological treatments for addiction as well as gaining important knowledge of neural mechanisms of moti-vated behaviors. In experimental animals previously treated with opioids, the precipitation of a range of withdrawal signs by acute injection of opioid antagonists is considered a model for studying opioid dependence (Bläsig et al., 1973, Koob et al., 1992; Martin et al., 1963). NPY is a 36 amino acid polypeptide that is widely and abundantly distributed in the central nervous system (Tatemoto et al., 1982). Several char-acteristics of NPY are suggestive of a potential role in treat-ment or in basic mechanisms of opioid dependence. For in-stance, NPY neurons and/or binding sites are located in brain regions (Chronwall et al., 1985; de Quidt and Emson, 1986; Dumont et al., 1992) implicated in expression of opioid with-drawal, e.g., periaqueductal gray, hypothalamus and locu