ANALYSIS OF SUPERSENSITIVITY IN THE ISOLATED SPLEEN OF THE CAT

¹ Department of Pharmacology, West Virginia University Medical Center, Morgantown, West Virginia

In vitro experiments were performed in which dose-response curves to d-norepinephrine or l-norepinephrine, pA₂ values for l-NE-phentolamine and pD'₂ values for l-NE-phenoxybenzamine were determined in separate strips cut from each spleen. Denervation and cocaine (in reserpine-pretreated preparations) produced supersensitivity to l-NE but not to d-NE. Reserpine (0.1 mg/kg for 14 days) did not produce supersensitivity to l-NE. Reserpine (1.0 mg/kg for 2 days) produced subsensitivity to d-NE. The pA₂ and pD'₂ values in all groups were not significantly different from control. Tissue NE concentrations were approximately 10% of control 14 days after denervation and after chronic treatment with reserpine. Results are presented which indicate that the innervation of the spleen is not homogeneous and that the denervation procedure employed produced a complete denervation of the wide or medial end of the spleen but only a partial denervation of the thin or lateral end. It is concluded that the supersensitivity of the isolated spleen observed after denervation or cocaine is of presynaptic origin. Postsynaptic supersensitivity after chronic denervation or chronic reserpine treatment, although demonstrable in other tissues, could not be demonstrated in the spleen.