Characterization of electrocorticographic, electromyographic and electrocardiographic recordings after the use of caffeine in Wistar rats

Abstract

Objective: To describe electrocorticographic, electromyographic and electrocardiographic profiles to report the electrophysiological effects of caffeine in Wistar rats.

Methods: Male adult Wistar rats weighing 230g to 250g were used. Rats were allocated to one of two groups, as follows: Group 1, Control, intraperitoneal injection of 0.9% saline solution (n=27); and Group 2, treated with intraperitoneal injection of caffeine (50mg/kg; n=27). The rats were submitted to electrocorticographic, electromyographic and electrocardiographic assessment.

Results: Brain oscillations (delta, theta, alpha, beta and gamma) in the frequency range up to 40Hz varied after caffeine administration to rats. Powers in delta and theta oscillations ranges were preponderant. The contractile force of the skeletal striated and cardiac muscles increased. Electrocardiogram analysis revealed shorter RR, QRS and QT intervals under the effect of caffeine.

Conclusion: In the central nervous system, there was an increase in the delta, theta and alpha amplitude spectrum, which are related to memory encoding and enhanced learning. With regard to skeletal muscle, increased contraction of the gastrocnemius muscle was demonstrated, a clear indication of how caffeine can be used to enhance performance of some physical activities. Electrocardiographic changes observed after caffeine administration are primarily related to increased heart rate and energy consumption.

Figure 1. Recording of electrocorticograms in the Control Group and the Caffeine-Treated Group. A) Electrocorticogram of the Control Group, with expansion of the tracing that reveals power intensity at frequencies below 10Hz; B) Electrocorticographic recording obtained after intraperitoneal administration of 50mg/kg of caffeine where there is a predominance of frequencies above 10Hz; C) Spectral energy distribution after intraperitoneal administration of caffeine (50mg/kg) or saline solution (control) and their respective cerebral oscillations. Data were analyzed by comparing means, using the t test followed by the Mann-Whitney test, with a significance level of p<0.001 (n=9)

Figure 2. Average power range of delta, theta, alpha, beta and gamma brain oscillations in the Control and Caffeine-Treated Groups (50mg/kg). A) Powers of the predominant brain waves in the Control Group; B) Predominant potencies in brain oscillations in animals that received intraperitoneal caffeine; C) Comparison of the oscillations detected in each group (n=9)

Figure 3. Electroneuromyographic recording of gastrocnemius muscle contraction. The registration time was 300 seconds. A) Registration of animals in the Control Group; B) Registration after caffeine administration; C) The power observed in the complete recording at frequencies up to 50Hz demonstrates the power of muscle contractions measured in control and caffeine-treated animals; D) Power of the strongest contractions recorded in the Control and Treated Caffeine Groups, at a fixed time of 5 seconds of contraction (n=9)

Figure 4. Animals' electrocardiogram and enlargement of the electrocardiographic tracing. A) Control group tracing in lead D-II; B) Electrocardiogram of the Caffeine-treated Group in lead D-II; C) Expansion of the interval from 40 to 50 seconds for the Control Group; D) The interval between 40 and 50 seconds of the electrocardiogram of animals treated with caffeine is extended; E) Electrocardiogram tracing of rats in sinus rhythm in lead D-II, showing the analyzed intervals, 1 second of increase; F) Electrocardiographic tracing of the Group Treated with Caffeine, demonstrating the characteristics of cardiac deflagration and shortening of the R-R interval, 1 second of increase

Figura 1. Registro dos eletrocorticogramas do Grupo Controle e do Grupo Tratado com Cafeína. A) Eletrocorticograma do Grupo Controle, com ampliação do traçado que revela intensidade de potência nas frequências abaixo de 10Hz; B) Registro eletrocorticográfico obtido após a administração intraperitoneal de 50mg/kg de cafeína onde há um predomínio nas frequências acima de 10Hz; C) Distribuição de energia espectral após a administração intraperitoneal de cafeína (50mg/kg) ou solução fisiológica (controle) e as suas respectivas oscilações cerebrais. Os dados foram analisados por comparação de médias, empregando-se o teste t seguido do teste de Mann-Whitney, com nível de significância de p<0,001 (n=9)

Figura 2. Amplitude média de potência das oscilações cerebrais delta, teta, alfa, beta e gama nos Grupos Controle e Tratado com Cafeína (50mg/kg). A) Potências das ondas cerebrais predominantes no Grupo Controle; B) Potências predominantes nas oscilações cerebrais nos animais que receberam cafeína por via intraperitoneal; C) Comparação das oscilações detectadas em cada grupo (n=9)

Figura 3. Registro eletroneuromiográgico da contração do músculo gastrocnêmio. O tempo de registro foi de 300 segundos. A) Registro dos animais do Grupo Controle; B) Registro após a administração de cafeína; C) A potência observada no registro completo em frequências de até 50Hz demonstra a potência das contrações musculares mensuradas nos animais controle e tratados com cafeína; D) Potência das contrações mais fortes registradas nos Grupos Controle e Tratado com Cafeína, em tempo fixo de 5 segundos de contração (n=9)

Figura 4. Eletrocardiograma dos animais e ampliação do traçado eletrocardiográfico. A) Traçado do Grupo Controle na derivação D-II; B) Eletrocardiograma do Grupo Tratado com Cafeína na derivação D-II; C) Ampliação do intervalo de 40 a 50 segundos do Grupo Controle; D) O intervalo entre 40 e 50 segundos do eletrocardiograma dos animais tratados com cafeína está ampliado; E) Traçado do eletrocardiograma dos ratos em ritmo sinusal na derivação D-II, mostrando os intervalos analisados, 1 segundo de aumento; F) Traçado eletrocardiográfico do Grupo Tratado com Cafeína, demonstrando as características da deflagração cardíaca e encurtamento do intervalo R-R, 1 segundo de aumento