Vascular resistance in the perfused isolated rat tail

Area of Science:

• Physiology
• Pharmacology
• Cardiovascular Research

Background:

• Understanding resistance vessel behavior is crucial for cardiovascular drug development.
• Existing methods for studying vascular responses can be complex or costly.

Purpose of the Study:

• To develop and validate a simple, cost-effective constant flow perfusion system using the isolated rat tail.
• To investigate the behavior of resistance vessels and the effects of various vasoactive agents and conditions.

Main Methods:

• Utilized a constant flow perfusion system with an isolated rat tail preparation.
• Employed dialyzed bovine serum albumen in the perfusion medium to maintain osmotic pressure and ensure stable baseline resistance.
• Administered various vasoactive agents (e.g., noradrenaline, angiotensin II) and stimulated sympathetic nerves.
• Investigated the effects of temperature and propranolol concentrations on vascular responses.

Main Results:

• The system maintained stable baseline resistance for several hours, with reproducible dose-response curves.
• Noradrenaline, adrenaline, serotonin, vasopressin, angiotensin II, high potassium, and sympathetic nerve stimulation caused vasoconstriction.
• Angiotensin I, bradykinin, histamine, acetylcholine, and isoprenaline did not affect baseline vascular resistance.
• Maximal sensitivity to noradrenaline was observed between 32-34°C; lower temperatures increased resting tone and prolonged noradrenaline's pressor effect.
• Low propranolol concentrations enhanced vasoconstriction by adrenaline and noradrenaline, while high concentrations had a direct pressor effect.

Conclusions:

• The isolated rat tail perfusion system provides a stable and reproducible model for studying resistance vessel behavior.
• This preparation is a simple, inexpensive, and effective adjunct for investigating vasoactive drug actions and physiological conditions affecting vascular resistance.