Differential effects of ACTH4-10, DG-AVP, and DG-OXT on heart rate and passive avoidance behavior in rats

Emotional remodeling with oxytocin durably rescues trauma-induced behavioral and neuro-morphological changes in rats: a promising treatment for PTSD

Recent evidence indicates that reactivated memories are malleable and can integrate new information upon their reactivation. We injected rats with oxytocin to investigate whether the delivery of a drug which dampens anxiety and fear before the reactivation of trauma memory decreases the emotional load of the original representation and durably alleviates PTSD-like symptoms. Rats exposed to the single prolonged stress (SPS) model of PTSD were classified 15 and 17 days later as either resilient or vulnerable to trauma on the basis of their anxiety and arousal scores. Following 2 other weeks, they received an intracerebral infusion of oxytocin (0.1 µg/1 µL) or saline 40 min before their trauma memory was reactivated by exposure to SPS reminders. PTSD-like symptoms and reactivity to PTSD-related cues were examined 3-14 days after oxytocin treatment. Results showed that vulnerable rats treated with saline exhibited a robust PTSD syndrome including increased anxiety and decreased arousal, as well as intense fear reactions to SPS sensory and contextual cues. Exposure to a combination of those cues resulted in c-fos hypo-activation and dendritic arbor retraction in prefrontal cortex and amygdala neurons, relative to resilient rats. Remarkably, 83% of vulnerable rats subjected to oxytocin-based emotional remodeling exhibited a resilient phenotype, and SPS-induced morphological alterations in prelimbic cortex and basolateral amygdala were eliminated. Our findings emphasize the translational potential of the present oxytocin-based emotional remodeling protocol which, when administered even long after the trauma, produces deep re-processing of traumatic memories and durable attenuation of the PTSD symptomatology.

Improvements in the selective perception and training of rats using an original analog of the C-terminal fragment of vasopressin

This report presents studies on the effects of intranasal administration of five doses (0.001, 0.01, 0.1, 1, and 10 microg/kg) of a new analog of arginine-vasopressin fragment AVP(6-9), i.e., D-MPRG, on the learning ability of rats with positive and negative reinforcement. All doses of the peptide improved learning. The most effective dose was 0.01 microg/kg, at which the peptide accelerated the acquisition of a conditioned active avoidance reflex both when given 1 h before and when given immediately after training sessions. The peptide had greater effects when animals were trained with negative reinforcement. Analysis of the results suggests that the action of D-MPRG is mainly on perception processes, i.e., extraction of the conditioned stimulus from the environmental surroundings and evaluation and enhancement of its biological significance. In addition, this peptide prevented extinction of the acquired habit and improved the processes of consolidation, though this effect was weaker than its effect on perception.

The effects of pregnenolone sulfate and ethylestrenol on retention of a passive avoidance task

Two experiments using male rats evaluated the effects of a range of doses of the neurosteroid, pregnenolone sulfate (PS), or of the synthetic neurosteroid, ethylestrenol (E), on the retention of a passive avoidance task. The steroids either were given immediately after the training trial or 1 h before the first retention test. Retention tests were given both 24 h and 48 h after acquisition. In both experiments, separate groups of animals were trained under low or moderate footshock conditions. At all doses tested both PS and E improved retention under the low footshock conditions. In groups trained with the higher footshock, the steroid-treated groups performed no better than the vehicle controls. Indeed, there were suggestions that some doses impaired retention. These results seem best understood as an induction of bimodality or 'turbulence' in behavior as used in Chaos theory rather than a shift in an inverted U-shaped retention function. In the second experiment in which the steroids were given before retention testing, they were generally without effect.

Effects of intranasal vasopressin and oxytocin on physiologic responding during personal combat imagery in Vietnam veterans with posttraumatic stress disorder

This study measured heart rate, skin conductance, and lateral frontalis electromyographic (EMG) responses in 43 male Vietnam veterans with posttraumatic stress disorder during personal combat imagery. In a double-blind research design, subjects were randomly assigned to receive intranasal arginine vasopressin (20 IU), placebo, or oxytocin (20 IU) an hour before the experiment. The group order of physiologic responding was as predicted: vasopressin > placebo > oxytocin. The most specific effect was exerted by vasopressin on EMG responses. This drug effect was not accounted for by nonspecific changes in responsiveness. Results are consistent with enhancing and inhibiting effects on memory retrieval and conditioned responding of vasopressin and oxytocin, respectively.