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Ventricular arrhythmia evoked by microinjection of picrotoxin into brain areas in rabbits
Abstract:
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.
Insights
This study identifies the posterior hypothalamus and medial tuberal region as key brain areas inducing arrhythmia. Both the sympathetic and parasympathetic nervous systems play a role in arrhythmia development.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
Background:
- Picrotoxin (Pic) is known to induce cardiac arrhythmias.
- Identifying specific brain regions involved in drug-induced arrhythmias is crucial for understanding autonomic nervous system regulation of the heart.
Purpose of the Study:
- To pinpoint the precise brain areas responsible for picrotoxin (Pic)-induced cardiac arrhythmias.
- To elucidate the neural pathways and systems involved in the genesis of these arrhythmias.
Main Methods:
- Anesthetized rabbits received microinjections of a low dose of picrotoxin (Pic) into various brain regions.
- Pharmacological interventions including vagotomy, phentolamine, diazepam, and adrenalectomy were employed.
- Phentolamine or diphenhydramine were microinjected into the posterior hypothalamus (PH) before Pic administration.
Main Results:
- Microinjection of Pic into the posterior hypothalamus (PH) and medial tuberal region rapidly induced arrhythmia.
- Ventricular arrhythmia was suppressed by vagotomy, phentolamine, diazepam, and adrenalectomy.
- Pretreatment with phentolamine or diphenhydramine in the PH delayed the onset of arrhythmia.
Conclusions:
- The posterior hypothalamus (PH) and medial tuberal region are critical for picrotoxin (Pic)-induced arrhythmia.
- Both the sympathoadrenomedullary and parasympathetic nervous systems are implicated in the development of these cardiac arrhythmias.