Effects of vasopressin on open-field behavior in rats

Central administration of corticotropin-releasing hormone stimulates locomotor activity in juvenile chinook salmon (Oncorhynchus tshawytscha)

This study evaluated the effect of corticotropin-releasing hormone (CRH) on locomotor activity, habitat choice, and social behavior in juvenile spring chinook salmon (Oncorhynchus tshawytscha). An intracerebroventricular (ICV) injection of CRH caused a dose-dependent increase in locomotor activity. The stimulatory effect of exogenous CRH on locomotor activity lasted for at least 24 h. Injection (ICV) of a peptide antagonist of CRH, alpha-helical CRH(9-41) (ahCRH), prevented the increase in locomotor activity when administered concurrently with CRH. Furthermore, fish administered the antagonist alone had significantly lower locomotor activity levels compared to saline-injected control fish. The effects of CRH are often dependent on the social context. However, no evidence was found that the presence of conspecifics during the testing procedure affected locomotor activity following ICV injections of CRH. Similarly, ICV injections of CRH or ahCRH did not have a significant effect on the mean time spent in contact with a conspecific. However, the position of fish in the tank was affected by the treatments. ICV injections of CRH significantly increased the amount of time that fish spent near the center of the tank. Furthermore, ICV injections of ahCRH significantly increased the mean time taken for fish to find cover in the tank. The effect of CRH and ahCRH on locomotor activity was not related to changes in plasma cortisol or thyroxine. These results support the hypothesis that endogenous CRH within the central nervous system is involved in the stimulation of locomotor activity in fish. Furthermore, CRH may also alter habitat choice in a novel environment.

Food-restriction interacts with vasopressin modulation of activity

The effects of peripheral injection of various doses of lysine-vasopressin (LVP), administered 30 min before a 5-min session in a hole-board apparatus, were compared as a function of food restriction. Comparison of performance for various indices of general activity clearly showed that the food-restricted rats were more active and exhibited less photophobia than normally fed ones. The differences between the two groups were maintained in a second session 24 hours later. There was no sign of behavioral habituation to the apparatus among restricted animals. Different doses (0.2, 1, 2 micrograms of LVP) affected food-restricted animals differently from the rats fed ad lib. Only the highest dose reduced activity in both groups. A posttest injection of the smallest dose (0.2 micrograms) had an opposite effect on the activity in the hole-board, measured 24 hours after the injection. A second experiment showed that plasma and adrenal corticosterone were higher in deprived rats. The administration of 0.2 micrograms of LVP was followed by an increase in corticosterone. In food-restricted rats this increase was bigger and was still observed 24 hours after the injection. There is an interaction between feeding conditions and LVP injections which affects both the internal hormonal state and spontaneous reactivity to environment. These findings are of relevance to the effect of vasopressin on behavior.

Effects of vasopressin on spontaneous black-white choices in a T-maze

The effects of subcutaneous administration of vasopressin on spontaneous black-white choice were investigated to determine whether they could account for modifications of performances during learning. First, pretrial injections of 0.2 microgram of lysine-vasopressin (LVP) were given to rats fed ad lib submitted after the last injection to ten consecutive choices in the T-maze. Rats received one or five injections and were tested after either 30 minutes or 24 hours. Treatment with LVP reduced natural photophobia and modified the activity. A more striking effect was observed after one injection and with an injection-test interval of 30 min. Second, the influence of repeated injections of LVP on free choices was studied in food-motivated rats. The effect of repeated injections was marked, suggesting greater sensitivity to treatment in such rats. Third, we compared the action of posttrial administration of the peptide on the behavior of food-restricted rats submitted to appetitive learning in the T-maze, or to free choices. The treatment slightly disturbed the learning of the white arm and altered the preference for black in free choices condition. The two actions were different, showing that the effect on spontaneous behavior cannot account for the effect on learning.

Electric footshocks differentially affect plasma and spinal cord vasopressin and oxytocin levels

Rats exposed for three minutes to repeated electric footshocks showed an approximate 10-fold increase of basal plasma vasopressin (AVP) and oxytocin (OXT) levels. In contrast, spinal AVP and OXT contents measured in the same rats remained unchanged when compared to undisturbed controls. This observation suggests that spinal AVP and OXT do not play a major role in the short-term adaptation of the organism to stress.

Effects of vasopressin on noradrenaline-induced cyclic AMP accumulation in rat brain slices

Addition of arginine vasopressin (AVP) or 1-desamino-8-D-arginine vasopressin (DDAVP) to rat cortical slices resulted in significant inhibition of the rise in cyclic AMP produced by incubation with 50 microM noradrenaline. A single injection of DDAVP (20 micrograms/rat) produced a reduced response to noradrenaline in derived cortex and caudate slices. In animals pretreated at day 5 of life with IP desipramine and intracisternal 6-hydroxydopamine (6-OHDA), both acute and chronic treatments with DDAVP resulted in a reduction in response in derived cortical, caudate and hippocampal slices. The 6-OHDA pretreated animals also showed reduced open-field behavioural activity after both acute and chronic DDAVP, while animals which were not pretreated responded to acute treatment only. The relationship between the effects of vasopressin on noradrenaline-induced cyclic AMP accumulation and its action on learning and memory is discussed.

Effects of vasopressin deficiency, age, and stress on stomach ulcer induction in rats

Susceptibility to ulceration induced by restraint, restraint plus intermittent shock, and activity stress was studied in 6 week and 18 week old Brattleboro and Long-Evans rats. Older animals developed more glandular ulcers than younger animals with Brattleboro rats having significantly greater ulceration than Long-Evans rats in both conditions. With activity stress, younger subjects developed significantly more glandular ulcers than older subjects; whereas, older subjects developed significantly more nonglandular ulcers than younger subjects. In both instances, the ulceration was significantly greater in Brattleboro rats than in Long-Evans rats. There were significantly high correlations among running behavior, survival time, and the development of glandular ulcers in younger animals exposed to activity stress. The presence of vasopressin, as well as the age of the subject and the nature of the stress, influences the type and degree of stomach pathology induced.

Corticotropin-releasing factor (CRF) stimulates locomotor activity in intact and hypophysectomized newts (Amphibia)

Locomotor activity of rough-skinned newts (Taricha granulosa) was significantly higher in intact and hypophysectomized males injected intracranially with 100 ng CRF (ovine corticotropin-releasing factor) than in those injected with 10 ng CRF or saline. In addition, an injection of corticosterone or dexamethasone failed to stimulate newt locomotor activity. These results provide evidence that CRF can act independently of pituitary hormones to stimulate locomotor activity in a nonmammalian vertebrate.

Dose-related influence of arginine-vasopressin on a passive avoidance behavior: effect of rearing conditions

The present experiment was conducted in order to determine what effects administration of arginine-vasopressine (AVP) would have on post weaned male rats, reared for 44 days either in relative social isolation or in group and tested in a cross-through passive avoidance task. AVP (0.0; 0.1 and 1.0 micrograms/rat) was injected subcutaneously immediately after the application of the electric footshock (0.3 mA for 2 sec). The individual post-weaning housing significantly impaired the passive avoidance performance in rats treated with saline (0.0 micrograms) and in rats treated with 1.0 micrograms AVP. No difference, however, was observed between isolated and group-reared rats injected with 0.1 micrograms AVP. It was concluded that AVP acts upon the passive avoidance performance by changing the animal's state of arousal in a non-monotonic dose-dependent manner.

Effect of daily pretrial injection of oxytocin on rat behavior in the open-field situation

This experiment was conducted to investigate the effects of daily pretrial intraperitoneal injection of oxytocin on behaviors of rats in an open-field situation. The group treated with 0.055 micrograms of oxytocin did not show any behavioral changes except the defecation score which was significantly more elevated than in controls. The group treated with 0.11 micrograms showed a general locomotor activity and a number of rearing behavior significantly more elevated than in all three other groups. The defecation and the grooming scores were however not different from controls. Finally, the group treated with 0.22 micrograms did not present any behavioral difference when compared with controls. Only the defecation score was significantly lower than in all the other groups. It is suggested that daily injection of oxytocin affects the arousal rather than the emotionality level.

Peripheral neurophysins changes under mild stress conditions

Total immunoreactive neurophysins levels increased significantly in rats after they had been trained in a situation based on the innate light-dark avoidance principle. These levels varied according to the amount of 'familiarisation cues' which characterised the situation. The results are discussed in terms of arousal/stress-neurophysins relationships.