Ventricular arrhythmia evoked by microinjection of picrotoxin into brain areas in rabbits.
To explore the main areas of brain responsible for arrhythmia evoked by icv picrotoxin (Pic), a very small dose of Pic (3 micrograms) was injected into different areas of brain in anesthetized rabbits. The short latency of arrhythmia was found after microinjection of Pic into posterior hypothalamus (PH, 5.6 +/- 0.9 min) and the medial part of tuberal region (7.5 +/- 2.9 min). The ventricular arrhythmia was abolished by vagotomy, iv phentolamine or diazepam, or pretreatment with adrenalectomy or vagotomy. Microinjection of phentolamine or diphenhydramine into PH prior to Pic postponed the arrhythmia. The results indicate that PH and the medial part of tuberal region are the most effective areas for Pic to induce arrhythmia, activations of both sympathoadrenomedullary and parasympathetic systems are involved in the genesis of arrhythmia.