Atrial Natriuretic Factor/metabolism; Dopamine/pharmacology; Receptors, Dopamine D1/metabolism; Receptors, Dopamine D2/metabolism; 1-Methyl-3-isobutylxanthine/pharmacology; 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology; Adenylyl Cyclases/metabolism; Animals; Antibodies; Atrial Natriuretic Factor/analysis; Atrial Natriuretic Factor/immunology; Benzazepines/pharmacology; Biological Transport/drug effects; Biological Transport/physiology; Blotting, Northern; Bucladesine/pharmacology; CHO Cells; Cells, Cultured; Colforsin/pharmacology; Cricetinae; Dopamine Agonists/pharmacology; Dopamine Antagonists/pharmacology; GTP-Binding Proteins/metabolism; Gene Expression/drug effects; Gene Expression/physiology; Hypothalamus/cytology; In Situ Hybridization; Intercellular Signaling Peptides and Proteins; Ligands; Neurons/chemistry; Neurons/cytology; Neurons/enzymology; Peptides; Phosphodiesterase Inhibitors/pharmacology; Quinpirole/pharmacology; RNA, Messenger/analysis; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1/genetics; Receptors, Dopamine D2/genetics; Receptors, Dopamine D5; Staining and Labeling; Wasp Venoms/pharmacology