Cardiovascular Responses Produced by the Systemic Injection of Kainic Acid in Conscious Wky and Sh Rats

Abstract

This study examined the cardiovascular effects of systemic injections of the excitatory amino acid analogue (EAA) kainic acid (KA) in conscious normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats. The injection of KA (100–1000 μg/kg, i.v.) produced dose-dependent but transient pressor and tachycardic responses followed by a prolonged period of bradycardia in both strains. Higher doses of KA also produced a secondary prolonged depressor response in WKY but not SH rats. Pharmacological studies demonstrated that the pressor and tachycardic responses are due mainly to increased sympathetic drive to the vasculature and heart. The KA-induced depressor response in the WKY is due principally to cardiovagal activation. After ganglionic blockade, KA produced a prolonged pressor response which was due to the release of vasopressin. These results indicate that the systemic administration of EAAs may produce their cardiovascular effects by activation of the autonomic nervous and endocrine systems and that the absence of the KA-induced hypotension in the SH rats may be related to an abnormality of cardiovagal function in this strain.

Key Words:

• Kainic acid
• intravenous
• blood pressure
• heart rate
• spontaneously hypertensive rat