The analgesic effects of intracerebroventricularly (i.c.v.) administered dynorphin A(l-13) and its analog dynorphin A(l-10)amide using the hot plate test were studied in mice. Both dynorphins applied i.c.v. by the freehand method had an analgesic effect but no effect was seen when applied i.c.v. through an implanted cannula. Moreover, freehand i.c.v. injection of saline increased the time of immobility in the forced swimming test and glycaemia levels compared with intact mice. In contrast to the freehand injection, saline administration through an implanted cannula did not influence the immobility of animals in forced swimming test when compared with the intact controls. These results suggest that 1) the freehand method is very stressful procedure of administration which could influence the effects of dynorphins in the hot plate test and 2) dynorphins exert an analgesic effect in the hot plate test only when combined with a stressor (freehand i.c.v. injection).
Dynorphin A (1-13) and its analog dynorphin A (1-10) amide were applied intracerebroventricularly in male ICR mice. Both dynorphins did not reveal any analgesic activity in tail-flick test under normal (non-stressed) conditions. However, in combination with stress (forced swimming or whole body vibration) both dynorphins prolonged tail- flick latencies when compared with stressed saline controls. Naloxone inhibited the effect of dynorphins in forced swimming test. Neither dynorphin A (1-13) nor dynorphin A (1-10) amide increased tail-flick latencies when combined with weak immobilization stress. Our results suggest that the analgesic effects of dynorphins are potentiated by strong stressors.
Oxytocin is a hormone therapeutically used mainly for its peripheral effects during pregnancy in the uterus and breasts. However, additional central effects, i.e. anxiolytic effect, decreased level of social stress and increased empathy have been also observed. Hence, the aim of our study was to evaluate if nasal oxytocin can be used as anxiolytic substance in rhesus monkeys (n=20) and rabbits (n=20). Simultaneously, mean
arterial blood pressure, arterial oxygen saturation of hemoglobin and pulse rate were monitored in all the evaluated animals. While rabbits lost righting reflex, monkeys developed a dose-dependent loss of aggressiveness and/or anxiety as evaluated by behavioral methods (aggressive behavior was classified as non-sedated ‒ sedated ‒ strongly sedated)