GHB temporarily inhibits the release of dopamine in the brain. This may cause increased dopamine storage, and later increased dopamine release when the GHB influence wears off [Chin and Kreutzer, 1992]. This effect could account for the middle-of-the-night wakings common with use of higher GHB doses, and the general feelings of increased well-being, alertness and arousal the next day.
GHB also stimulates pituitary growth hormone (GH) release. One methodologically rigorous Japanese study reported nine-fold and sixteen-fold increases in growth hormone 30 and 60 minutes respectively after intravenous administration of 2.5 grams of GHB in six healthy men between the ages of twenty-five and forty [Takahara, 1977]. GH levels were still seven-fold higher at 120 minutes. The mechanism by which GHB stimulates growth-hormone release is not known. Dopamine activity in the hypothalamus is known to stimulate pituitary release of growth hormone, but GHB inhibits dopamine release at the same time that it stimulates GH release. This suggests that GHB’s GH-releasing effect takes place through an entirely different mechanism [Takahara, 1977]. At the same time GH is being released, prolactin levels also rise. Serum prolactin levels increase in a similar time-dependent manner as GH, peaking at five-fold above baseline at 60 minutes [Takahara, 1977]. This effect, unlike the release of GH, is entirely consistent with GHB’s inhibition of dopamine. Other compounds which lessen dopamine activity in the brain (such as the neuroleptic Thorazine) have been shown to result in prolactin release. Although prolactin tends to counteract many of the beneficial effects of GH, the sixteen-fold increases in GH probably overwhelm the five-fold increases in prolactin.
GHB induces “remarkable hypotonia” (muscle relaxation) [Vickers, 1969]. It is now gaining popularity in France and Italy as an aid to childbirth. GHB causes “spectacular action on the dilation of the cervix,” decreased anxiety, greater intensity and frequency of uterine contractions, increased sensitivity to oxytocic drugs (used to induce contractions), preservation of reflexes, a lack of respiratory depression in the fetus, and protection against fetal cardiac anoxia (especially in cases where the umbilical cord wraps around the fetus’ neck) [Vickers, 1969; Laborit, 1964]. GHB is completely metabolized into carbon dioxide and water, leaving absolutely no residue of toxic metabolites [Vickers, 1969; Laborit, 1972]. Metabolism is so efficient that GHB can no longer be detected in urine four to five hours after it is taken by injection [Laborit, 1964]. GHB activates a metabolic process known as the “pentose pathway” which plays an important role in the synthesis of protein within the body [Laborit, 1972]. It also causes a “protein sparing” effect [Laborit, 1964] which reduces the rate at which the body breaks down its own proteins. These properties, along with GHB’s effect on growth hormone, underlie its common use as an aid to muscle-building and fat loss.
Anesthetic (large) doses of GHB are accompanied by a small increase in blood sugar levels, and a significant decrease in cholesterol. Respiration becomes slower and deeper. Blood pressure may rise or fall slightly, or remain stable, but a moderate bradycardia (slowing of the heart) is consistent [Vickers, 1969; Laborit, 1964]. A slight drop in body temperature also occurs [Laborit, 1964].
GHB also stimulates the release of acetylcholine in the brain [Gallimberti, 1989].