ABSTRACT
BACKGROUND: Pigmented and albino rabbits are commonly used in visual research; however, the lack of pigment in the eyes may affect retinal responses. Here, we compare and describe the differences of retinal function between pigmented (English Butterfly) and albino (New Zealand) rabbits. METHODS: Electroretinograms were recorded in pigmented and albino rabbits in the dark-adapted eye, in the light-adapted eye and for four temporal frequencies in the light-adapted eye. The implicit time and amplitude of the a- and b-waves were analyzed, as well as the amplitude and phase of the first harmonic component of the photopic flicker response. RESULTS: Albino rabbits presented significantly larger amplitudes for both a- and b-waves at all intensities and frequencies. The intensity-response function of the scotopic b-wave also showed that the albino retina is more sensitive than the pigmented retina and the larger flicker amplitudes found in the albino group also revealed post-receptoral changes specifically related to cone pathways. CONCLUSIONS: The larger amplitude of albino receptoral and post-receptoral activities might be attributed to greater availability of light due to scatter and reflection at the retinal layer, and as the differences in response amplitudes between the groups increase with flicker frequency, we suggest that ON bipolar cells recover faster in the albino group, suggesting that this might be a mechanism to explain the higher temporal resolution for albinos compared to the pigmented group.
Subject(s)
Albinism, Oculocutaneous/physiopathology , Electroretinography , Rabbits/physiology , Retina/physiology , Animals , Color Vision/physiology , Dark Adaptation , Night Vision/physiology , Photic Stimulation , Retinal Cone Photoreceptor Cells/physiology , Skin PigmentationABSTRACT
OBJECTIVE: to determine the functional and morphological effects at rabbits retina of PS80 concentration used in the preparation of intravitreal drugs. METHODS: eleven New Zealand rabbits received a intravitreal injection of 0.1ml of PS80. As control, the contralateral eye of each rabbit received the same volume of saline. Electroretinography was performed according to a modified protocol, as well as biomicroscopy and retina mapping before injection and seven and ten days after. Animals were euthanized in the 30th day and the retinas were analyzed by light microscopy. RESULTS: eyes injected with PS80 did not present clinical signs of intraocular inflammation. Electroretinography did not show any alteration of extent and implicit time of a and b waves at scotopic and photopic conditions. There were no morphological alterations of retinas at light microscopy. CONCLUSION: intravitreal injection of PS80 in the used concentration for intravitreal drug preparations do not cause any functional or morphological alterations of rabbit retinas. These results suggest that PS80 is not toxic to rabbit retinas and may be safely used in the preparation of new lipophilic drugs for intravitreal injection.
Subject(s)
Polysorbates/administration & dosage , Retina/anatomy & histology , Retina/physiology , Animals , Electroretinography , Intravitreal Injections , Rabbits , Retina/drug effectsABSTRACT
ABSTRACT Objective : to determine the functional and morphological effects at rabbits retina of PS80 concentration used in the preparation of intravitreal drugs. Methods: eleven New Zealand rabbits received a intravitreal injection of 0.1ml of PS80. As control, the contralateral eye of each rabbit received the same volume of saline. Electroretinography was performed according to a modified protocol, as well as biomicroscopy and retina mapping before injection and seven and ten days after. Animals were euthanized in the 30th day and the retinas were analyzed by light microscopy. Results: eyes injected with PS80 did not present clinical signs of intraocular inflammation. Electroretinography did not show any alteration of extent and implicit time of a and b waves at scotopic and photopic conditions. There were no morphological alterations of retinas at light microscopy. Conclusion: intravitreal injection of PS80 in the used concentration for intravitreal drug preparations do not cause any functional or morphological alterations of rabbit retinas. These results suggest that PS80 is not toxic to rabbit retinas and may be safely used in the preparation of new lipophilic drugs for intravitreal injection.
RESUMO Objetivo: determinar os efeitos funcionais e morfológicos na retina de coelhos da concentração de PS80 utilizada na preparação de drogas intravítreas. Métodos: onze coelhos New Zealand receberam injeção intravítrea de 0,1ml de PS80. Como controle, o olho contralateral de cada coelho recebeu o mesmo volume de soro fisiológico. Foram realizados eletrorretinogramas de acordo com o protocolo modificado, biomicroscopia e mapeamento de retina antes da injeção, sete e dez dias depois. Os animais foram sacrificados no 30o dia e as retinas analisadas por microscopia de luz. Resultados: os olhos injetados com PS80 não apresentaram sinais clínicos de inflamação intraocular. O eletrorretinograma não apresentou alteração de amplitude e tempo implícito das ondas a e b nas condições escotópica e fotópica. Não houve alteração morfológica da retina na microscopia de luz. Conclusão: a injeção intravítrea de PS80 na concentração utilizada na preparação de drogas intravítreas não causa alterações funcionais e morfológicas na retina de coelhos. Esses resultados sugerem que o PS80 não é tóxico para a retina de coelhos e pode ser usado com segurança na preparação de novas drogas lipofílicas para injeção intravítrea.
Subject(s)
Animals , Polysorbates/administration & dosage , Retina/anatomy & histology , Retina/physiology , Rabbits , Retina/drug effects , Electroretinography , Intravitreal InjectionsABSTRACT
PURPOSE: To determine the half-life of mycophenolic acid (MPA) in the vitreous of New Zealand albino rabbits after intravitreal injection and the retinal toxicity of different doses of MPA. METHODS: Ten micrograms of MPA (Roche Bioscience, Palo Alto, CA) was injected in the vitreous of 16 rabbits, animals were sacrificed at different time-points, and vitreous samples underwent high-performance liquid chromatography. For functional and morphological studies, 5 doses of MPA (0.05, 0.5, 2, 10, and 100 µg) were injected in the vitreous of 20 rabbits. As control, contralateral eyes were injected with aqueous vehicle. Electroretinograms (ERGs) were recorded before injection and at days 7, 15, and 30. Animals were sacrificed on day 30 and retinas were analyzed under light microscopy. RESULTS: MPA half-life in the vitreous was 5.0±0.3 days. ERG revealed photoreceptor functional impairment in eyes injected with 0.5 µg and higher on day 30, while eyes injected with 100 µg presented the same changes already from day 15. No morphological change was found. CONCLUSIONS: MPA vitreous half-life is 5.0 days. Intravitreal injection of 0.5 µg MPA and higher causes dose- and time-related photoreceptor sensitivity decrease in rabbits. The MPA dose of 0.05 µg may be safe for intravitreal use in rabbits.
Subject(s)
Chromatography, High Pressure Liquid/methods , Immunosuppressive Agents/administration & dosage , Mycophenolic Acid/administration & dosage , Animals , Dose-Response Relationship, Drug , Electrophysiological Phenomena , Electroretinography , Half-Life , Immunosuppressive Agents/pharmacokinetics , Immunosuppressive Agents/toxicity , Intravitreal Injections , Mycophenolic Acid/pharmacokinetics , Mycophenolic Acid/toxicity , Photoreceptor Cells, Vertebrate/drug effects , Rabbits , Retina/drug effects , Retina/pathology , Time Factors , Vitreous Body/metabolismABSTRACT
OBJECTIVES: Acute retinal necrosis is a rapidly progressive and devastating viral retinitis caused by the herpesvirus family. Systemic acyclovir is the treatment of choice; however, the progression of retinal lesions ceases approximately 2 days after treatment initiation. An intravitreal injection of acyclovir may be used an adjuvant therapy during the first 2 days of treatment when systemically administered acyclovir has not reached therapeutic levels in the retina. The aims of this study were to determine the pharmacokinetic profile of acyclovir in the rabbit vitreous after intravitreal injection and the functional effects of acyclovir in the rabbit retina. METHODS: Acyclovir (Acyclovir; Bedford Laboratories, Bedford, OH, USA) 1 mg in 0.1 mL was injected into the right eye vitreous of 32 New Zealand white rabbits, and 0.1 mL sterile saline solution was injected into the left eye as a control. The animals were sacrificed after 2, 9, 14, or 28 days. The eyes were enucleated, and the vitreous was removed. The half-life of acyclovir was determined using high-performance liquid chromatography. Electroretinograms were recorded on days 2, 9, 14, and 28 in the eight animals that were sacrificed 28 days after injection according to a modified protocol of the International Society for Clinical Electrophysiology of Vision. RESULTS: Acyclovir rapidly decayed in the vitreous within the first two days after treatment and remained at low levels from day 9 onward. The eyes that were injected with acyclovir did not present any electroretinographic changes compared with the control eyes. CONCLUSIONS: The vitreous half-life of acyclovir is short, and the electrophysiological findings suggest that the intravitreal delivery of 1 mg acyclovir is safe and well tolerated by the rabbit retina.
Subject(s)
Acyclovir/pharmacokinetics , Antiviral Agents/pharmacokinetics , Retina/drug effects , Vitreous Body/metabolism , Animals , Disease Models, Animal , Electroretinography , Half-Life , Intravitreal Injections , Rabbits , Retina/physiology , Time FactorsABSTRACT
OBJECTIVES: Acute retinal necrosis is a rapidly progressive and devastating viral retinitis caused by the herpesvirus family. Systemic acyclovir is the treatment of choice; however, the progression of retinal lesions ceases approximately 2 days after treatment initiation. An intravitreal injection of acyclovir may be used an adjuvant therapy during the first 2 days of treatment when systemically administered acyclovir has not reached therapeutic levels in the retina. The aims of this study were to determine the pharmacokinetic profile of acyclovir in the rabbit vitreous after intravitreal injection and the functional effects of acyclovir in the rabbit retina. METHODS: Acyclovir (Acyclovir; Bedford Laboratories, Bedford, OH, USA) 1 mg in 0.1 mL was injected into the right eye vitreous of 32 New Zealand white rabbits, and 0.1 mL sterile saline solution was injected into the left eye as a control. The animals were sacrificed after 2, 9, 14, or 28 days. The eyes were enucleated, and the vitreous was removed. The half-life of acyclovir was determined using high-performance liquid chromatography. Electroretinograms were recorded on days 2, 9, 14, and 28 in the eight animals that were sacrificed 28 days after injection according to a modified protocol of the International Society for Clinical Electrophysiology of Vision. RESULTS: Acyclovir rapidly decayed in the vitreous within the first two days after treatment and remained at low levels from day 9 onward. The eyes that were injected with acyclovir did not present any electroretinographic changes compared with the control eyes. CONCLUSIONS: The vitreous half-life of acyclovir is short, and the electrophysiological findings suggest that the intravitreal delivery of 1 mg acyclovir is safe and well tolerated by the rabbit retina.
Subject(s)
Animals , Rabbits , Acyclovir/pharmacokinetics , Antiviral Agents/pharmacokinetics , Retina/drug effects , Vitreous Body/metabolism , Disease Models, Animal , Electroretinography , Half-Life , Intravitreal Injections , Retina/physiology , Time FactorsABSTRACT
Objetivo: Avaliar eletrofisiologicamente a função da retina do camundongo modelo de Alzheimer (3xTg-AD) comparando com seu controle (b6;129-PS1) em um estudo longitudinal com seis idades (2, 4, 6, 8, 10 e 12 meses). Métodos: Eletrorretinogramas (ERGs) foram registrados em 44 camundongos 3xTg-AD e em 23 controles, após administrada anestesia. Para o registro foi colocado um eletrodo de lente de contato sobre a córnea, um eletrodo de referência na cabeça e um terra na cauda. Em sessão de 30-40min de duração foram expostos ao seguinte protocolo de estimulação: 1) Adaptação ao escuro seguida de flashes nas intensidades: 0,003; 0,03; 0,3; 3 e 30 cd.s/m2; 2) Estimulação periódica (30 cd.s/m2) nas freqüências de 12, 18, e 30 Hz, sob luz de fundo (30 cd/m2). Resultados: Os ERGs mostraram dois tipos de respostas escotópicas tanto no grupo dos camundongos controles (b6;129- PS1) quanto nos modelos de Alzheimer. 13% dos camundongos controles e 72% dos modelos de AD apresentaram ERGs com potenciais oscilatórios presentes e tempo implícito da onda-b dentro da faixa esperada (45,31 ± 6,74 ms), enquanto no restante dos grupos, o ERG apresentou latência da onda-b muito aumentada (111,73 ± 22,56 ms) e potenciais oscilatórios ausentes. Devido a estes resultados, os grupos controle e experimental foram subdivididos em: b6;129 com OP, b6;129 sem OP; 3xTg-AD com OP e 3xTg-AD sem OP. Também foi incluído um grupo controle adicional constituído por 9 camundongos C57/B6. Comparando os cinco grupos, nenhuma diferença foi encontrada em relação à amplitude e à latência da onda-a. A amplitude da onda-b também foi semelhante para todos, ao contrário da latência para atingir o pico da onda-b dos grupos b6;129 sem OP e 3xTg-AD sem OP, que se apresentou duas vezes maior do que nos grupos com OP. As amplitudes dos cinco potenciais oscilatórios foram medidas individualmente e não mostraram diferenças entre os controles e os 3xTg-AD. (...)
... Para o estímulo periódico, a amplitude do 1º harmônico dos grupos com OP mostrou clara diferença entre os grupos controle e o 3xTg-AD, tanto em 12 Hz como em 18 Hz. Os resultados dos dois grupos controle b6;129 e C57/B6 mantiveram-se muito próximos. Os grupos sem OP mantiveram-se sempre próximos a 10 V para as três freqüências de estimulação e mostraram atraso na diferença de fase média do 1º harmônico em 18 e 30 Hz, indicando maior lentidão de resposta, quando comparados aos primeiros. Conclusão: O camundongo 3xTg-AD e seu controle (b6;129) apresentam uma variante lenta e sem OPs do ERG escotópico em parte da população. Células bipolares, amácrinas e ganglionares podem estar alteradas nesses subgrupos (b6;129 sem OP e 3xTg-AD sem OP). Os grupos controle e 3xTg-AD com OPs diferiram quanto à amplitude de resposta à estimulação intermitente, diferença essa que implica em menor capacidade de processamento temporal para o modelo de AD. Sugerimos que as células bipolares de cones podem estar alteradas nos modelos de AD devido às amplitudes mais baixas dos 1os harmônicos desse grupo
Objective: To evaluate electrophysiologically the function of the retina of the Alzheimer model mouse (3xTg-AD) comparing it with its control (b6;129-PS1) in a longitudinal study at six ages (2, 4, 6, 8, 10 e 12 months) Methods: Electroretinograms (ERGs) were recorded in 44 anesthetized mice 3xTg-AD and in 23 controls, with a contact lens electrode placed on the cornea, a reference electrode on the head and a ground on the tail. During a 30-40min duration session the mice were exposed to the following stimulation protocol: 1) Scotopic response Dark adaptation followed by flashes at the following intensities: 0,003; 0,03; 0,3; 3 e 30 cd.s/m2; 2) Periodic stimulation (30 cd.s/m2) at the temporal frequencies of 12, 18, e 30 Hz, under background light (30 cd/m2). Results: The ERGs showed two types of scotopic responses, which ocurred in both the control mice (b6;129- PS1) and the Alzheimer´s models (3xTg-AD). 13% of the controls and 72% of the Alzheimer´s models mice presented ERGs with oscillatory potentials (OPs) and b-wave implicit times within the expected range (45,31 ± 6,74 ms), while for the other groups the ERG presented a very delayed b-wave latency (111,73 ± 22,56 ms) and absence of OPs. Given these results, the control and experimental groups were subdivided into: b6;129 with OPs, b6;129 without OPs; 3xTg-AD with OPs e 3xTg-AD without OPs. An additional control group with 9 mice C57/B6 was included. Comparing the five groups, no difference was found in a-wave amplitude and latency. The b-wave amplitude also did not differ among the groups, but the latency of the b-wave for the groups b6;129 without OPs and 3xTg-AD without OPs, was twice as long as in the groups with OPs. The amplitudes of the five OPs, measured individually, did not show differences between controls and 3xTg-AD groups. For the periodic stimulation (...)
... the amplitude of the first harmonic of the Fourier transform of the groups with OPs showed a clear difference between the control and the 3xTg-AD groups, both for the 12 Hz and for the 18 Hz stimuli. The results of the two control groups (b6;129 and C57/B6) were very close. The groups without OPs had responses always close to 10 V for the three frequencies of stimulation and showed phase delay for the first harmonic, indicating response slowing, compared to the other groups. Conclusions: We found that a sub-group of both triple transgenic (3xTg-AD) and control mice (b6;129) manifest strikingly slow scotopic ERGs that lack OPs. We hypothesize that these response feature may reflect alterations in bipolar, amacrine and ganglion cells. The sub-group of triple transgenic and control mice that exhibited OPs differed in their response to flicker. Alzheimer model had significantly lower flicker-response amplitudes than the controls, suggesting impaired retinal temporal processing. We propose that the flicker results are consistent with alteration in cone bipolar cells in the Alzheimer model mice
