Facilitation of Extinction Retention and Reconsolidation Blockade by IV Allopregnanolone in PTSD- Pharmacokinetic Studies

Background: Allo is a neurosteroid (hormone) produced from progesterone by the brain, adrenal glands, testes, and ovaries. Production of Allo and its equally powerful, structurally similar, stereoisomer pregnanolone (PA) is stimulated when certain neurons in the brain are activated and when stress activates the adrenal glands. Allo and PA markedly increase effects of gamma-amino-butyric acid (GABA; an inhibitory neurotransmitter) in the brain, thereby regulating arousal and responses to stress. Allo and PA also influence processes that strengthen or weaken memories.

Basic research suggests that several factors can reduce production of Allo: exposure to chronic or extreme stress, prolonged social isolation, chronic intermittent heavy alcohol use, certain oral contraceptives, chronic use of some psychiatric medications or other substances used to manage PTSD such as nicotine, exposure to environment toxins, and genetic predisposition.

Research shows that Allo and PA production is reduced in a large subpopulation of women and men with PTSD. Reduced Allo and PA is strongly associated with severity and poor retention of extinction learning-both of which contribute to chronic PTSD. The proposed study thus will be conducted in adult men and women with chronic PTSD. Women will be studied during two distinct phases of the menstrual cycle because progesterone levels (and therefore levels of Allo and PA) change markedly across the menstrual cycle, as do problems with extinction retention.

Study Procedures: Eligible participants will take part in a widely used, standardized 3-day laboratory psychophysiology paradigm during which activation of the sympathetic nervous system (fight/flight system) is monitored via small electrode patches placed on the skin. The paradigm involves startle testing on Days 1, 2 and 3. During startle testing, participants will hear sudden bursts of white noise through headphones, see colored shapes on a computer screen, and feel sudden (not painful) blasts of air to the neck. The electrodes record participants' eye blinks, skin conductance, and heart rate. The startling sounds will be about as loud as a train but last only a fraction of a second. Participants will sit quietly with their eyes open as they listen. On study Day 2, participants are randomized by "luck of the draw" or chance to receive either IV Allo or placebo. On study Days 2 and 3, a brief memory test also will be conducted. Blood is collected each day for measurement of Allo, PA and other neurobiological factors that may affect the potential beneficial effects of Allo.

Before starting the above studies, the investigators will conduct pharmacokinetic (PK) studies in a small group of individuals with PTSD to confirm that the selected IV Allo dose increases blood Allo levels as expected.