In the ventral tegmental area, G-proteins mediate progesterone's actions at dopamine type 1 receptors for lordosis of rats and hamsters.
BACKGROUND
Previous reports indicate that the ventral tegmental area (VTA) and/or progesterone (P) can modulate the reinforcing effects of drugs of abuse, food, and sexual behavior.


OBJECTIVE
We investigated if, in the VTA, P's membrane-mediated actions for lordosis involve dopamine type 1 receptors (D(1)). Also, whether P's actions at D(1) for lordosis are mediated by typical G-protein coupled mechanisms was examined.


METHODS
In Exps 1 and 2, rats received estradiol (E(2) 10 microg) at h 0 and infusions of the D(1) antagonist SCH23390 (100 ng), the D(1) agonist SKF38393 (100 ng), or vehicle, to the VTA, at h 44. Thirty minutes later, rats received systemic P (0, 50, 100, or 200 microg). Subjects were tested for lordosis and motor behavior 2.5 h later. In Exps 3 and 4, E(2)+P (rats 0 or 100 microg; hamsters 200 microg)-primed animals were pretested for lordosis and motor behavior at h 47.5 and infused with SKF38393 (100 ng) or vehicle to the VTA. Thirty minutes later, subjects were retested and infused with the G-protein inhibitor guanosine 5'-O-(2-Thiodiphosphate) (GDP-beta-S; 50 microM) or vehicle. Post-testing occurred 30 min later.


RESULTS
Pretreatment with SCH23390-reduced and SKF38393-enhanced P's actions, in the VTA, for lordosis of E(2)-primed rats and hamsters. As well, D(1)-mediated increases in P-facilitated lordosis of rats and hamsters were inhibited by GDP-beta-S. Changes in lordosis were independent of large alterations in motor behavior.


CONCLUSIONS
In the VTA, P has actions for modulating reinforcing behaviors, such as lordosis, at D(1) that are G-protein-mediated.
Department of Psychology, The University at Albany, SUNY, Albany, NY, 12222, USA.
Sandra M
SM
Petralia
Cheryl A
CA
Frye
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D001552:Benzazepines / Q000494:pharmacology; D006224:Cricetinae; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008141:Lordosis / Q000378:metabolism / Q000503:physiopathology; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D020318:Rats, Long-Evans; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000378:metabolism
D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D017447:Receptors, Dopamine D1; D011374:Progesterone; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D019204:GTP-Binding Proteins