EFFECT OF CYCLIC PHENYL SALIGENIN PHOSPHATE AND PARAOXON TREATMENT ONVASCULAR-RESPONSE TO ADRENERGIC AND CHOLINERGIC AGENTS IN HENS

The response of peripheral blood vessels to adrenergic and cholinergic agonists was examined 1, 3, 7, and 21 d after hens were treated with a single intramuscular injection of 2.5 mg/kg cyclic phenyl saligenin phosphate (PSP) or 0.10 mg/kg paraoxon (PXN). These two organophosphat es (OPs) cause different clinical effects in exposed animals, as PSP c auses organophosphate-induced delayed neuropathy (OPIDN) and PXN cause s acute poisoning through inhibition of acetylcholinesterase. For thes e studies, the ischiadic artery was cannulated both prograde and retro grade and the blood was shunted through a pump to maintain a constant Now. Alterations in pressure measured at the pump outflow were used to indicate changes in limb vascular resistance. Dose-response curves we re generated for the response to intravenous administration of acetylc holine (ACh), phenylephrine (PE) or salbutamol (SAL) (10(-8) to 10(-4) mol/kg). Acetylcholine at 10(-8) to 10(-7) mol/kg caused an increase in vascular resistance, whereas concentrations of 10(-5) to 10(-4) mol /kg caused a decrease in vascular resistance in hens given PSP 1 and 3 d previously. The response of PXN-treated hens to ACh was not signifi cantly altered from that of vehicle-treated hens. The resistance gener ated in response to PE, an alpha(1)-adrenergic agonist, in PSF-treated hens was greater than levels in vehicle-treated hens on d 7 and 3 and greater than the response seen in hens treated with PXN. Salbutamol, a beta(2)-adrenergic agonist, at concentrations of 10(-7) to 10(-4) mo l/kg caused an increase in resistance 1 and 3 d after PSP and a decrea se on d 7. The-responses to SAL were different in PXN-treated hens, as these hens demonstrated a lesser increase in resistance at concentrat ions of 10(-8) to 10(-7) mol/kg and a decrease in resistance at 10(-5) to 10(-4) mol/kg 1 d after administration of PXN. These observations indicate that response to vasoactive agents is altered in OP-treated h ens and that responses differ between a compound capable of causing OP IDN (PSP) and a compound that only causes acute effects (PXN).