Influence of hemorrhagic shock on learning activity in the late posthemorrhagic period

Abstract

Anxiety and learning activity (acquisition of the conditioned behavior reaction trained with a bonus) were investigated in rats during 4 weeks after hemorrhagic shock. Some phasic behavioral alterations have been found in animals undergone hemorrhagic shock. Key words: hemorrhagic shock, arterial hypertension, anxiety, learningNotable alterations develop in animal behavior in the early posthemorrhagic period, manifested as worse memorization of experimental situation [2].Severe disturbances of ultrastructure and biochemical parameters in the cerebral cortex neurons occur in the late posthemorrhagic period [4]. They may bring about some impairments of the behavioral reactions in animals.We studied the process of learning in rats at different stages of the recovery period after hemorrhagic shock (HS). MATERIALS AND METHODSExperiments were performed on 91 outbred male albino rats (280-340 g). The animals, 6 to 7 in a cage, were housed in standard vivarium conditions with natural day-lighting. Arterial hypotension down to the mean pressure of 40 mmHg was produced in anesthetized rats (Nembutal, 40 mg/kg) by letting of the blood via a catheter inserted into the tail artery. Arterial pressure (AP) was maintained at this level during 1 hour, then the drained blood was reinfused. Learning consisted in acquisition of the food search learning task in T-maze [1] with arm length of 30 cm each. On day 1, deprived of food rats were placed for 1 h into the maze, where balls of bread were scattered, with the aim of adaptation and fatigue of orienting-exploratory activity. During the next 4 days animals were trained. Each day they were placed for 3 min or .less into the maze 5 times, successively. As a bonus were used bread balls. The following parameters were recorded: the latency (period between placing into and leaving starting compartment); the reaction time (the time needed for reaching and taking food); the number of mistakes