Is progesterone a pre-hormone in the CNS?

Area of Science:

• Neuroendocrinology
• Neuropharmacology
• Steroid hormone action

Background:

• Progesterone is a key steroid hormone with known central nervous system effects.
• Dopaminergic pathways in the corpus striatum are crucial for motor control and reward.
• The precise mechanisms of progesterone action on striatal dopamine are not fully elucidated.

Purpose of the Study:

• To investigate the modulatory effects of progesterone on presynaptic dopaminergic terminals in the rat corpus striatum.
• To determine if progesterone's effects are concentration and infusion mode dependent.
• To compare the action of progesterone and its metabolite pregnanolone in different brain regions.

Main Methods:

• Experimental administration of progesterone to rats.
• Assessment of dopamine terminal response to amphetamine stimulation.
• Measurement of tissue dopamine concentrations.
• In vitro and in vivo preparations of hypothalamic and striatal tissues.

Main Results:

• Progesterone's effect on dopamine terminals is concentration and infusion mode dependent.
• Low pulsatile progesterone doses enhance amphetamine-induced dopamine release and increase dopamine levels.
• Continuous or high-dose progesterone inhibits amphetamine-induced dopamine release and decreases dopamine levels.
• Pregnanolone, a progesterone metabolite, was ineffective in the corpus striatum but active in the hypothalamus.

Conclusions:

• Progesterone acts as a potent modulator of striatal dopaminergic terminals.
• The effects of progesterone are dose-dependent and exhibit distinct patterns based on pulsatile versus continuous administration.
• Site-specific mechanisms within the central nervous system differentially control progesterone's actions, with pregnanolone being key in the hypothalamus but not the striatum.