ABSTRACT
OBJECTIVE: To determine the cardiovascular actions of salusin-α in the caudal ventrolateral medulla (CVLM) in anesthetized rats. METHODS: Sixty-one anesthetic male SD rats were employed in the present study. The dose-dependant effects of salusin-α (0.04-4 pmol) on blood pressure and heart rate in the CVLM were determined by unilateral microinjection of salusin-α or artificial cerebrospinal fluid (aCSF) into the CVLM in 25 rats. In the other 36 rats, a CSF, kynurenic acid (Kyn), atropine, hexametho-nium (Hex) in the CVLM or a CSF/muscimol in the RVLM were given in advance to determine the mechanism of the cardiovascular actions of intra-CVLM salusin-α. RESULTS: Unilateral microinjection of salusin-a into the CVLM produced a dose-dependent hypotension and bradycardia. Prior administration of Kyn (1 nmol) or Hex (120 pmol) into the CVLM did not alter the hypotension and bradycardia induced by intra-CVLM salusin-α (P>0.05). But prior administration of atropine into the CVLM or pretreatment with muscimol within RVLM almost completely abolished the hypotension and bradycardia evoked by intra-CVLM salusin-α (P<0.05). CONCLUSION: Microinjection of salusin-α into the CVLM produces significantly hypotension and bradycardia, which probably originates from suppressing the activities of presympathetic neurons in the RVLM.