Diabetes Research and Clinical Practice 44 (1999) 93 – 100 Beneficial effect of thyrotropin-releasing hormone on neuropathy in diabetic rats Husamettin Gul a , Zeki Odabasi b , Oguzhan Yildiz a, *, Metin Ozata c , Gonen Deniz a , Okay Vural b , Askin Isimer a a Department of Medical Pharmacology, Gulhane School of Medicine, 06018, Ankara, Turkey b Department of Neurology, Gulhane School of Medicine, 06018, Ankara, Turkey c Department of Endocrinology and Metabolism, Gulhane School of Medicine, 06018, Ankara, Turkey Received 26 October 1998; received in revised form 15 December 1998; accepted 24 February 1999 Abstract Thyrotropin releasing hormone (TRH) is therapeutically effective in experimental and clinical spinal injury. The effects of TRH on diabetic neuropathy are not known. The aim of the present study was to investigate the electrophysiological effects of TRH in the streptozotocin diabetic rats. Three groups of rats were studied, non-diabetic control (n =10), diabetic controls (n =8), and TRH treated diabetic rats (n =9). Administration of TRH or saline and electrophysiological measurements were performed 4 weeks after induction of diabetes. TRH was given intraperitoneally in a dose of 600 g (3 ml). Nerve conduction velocity (NCV), measured in caudal nerve, and N 1 latency of somatosensory evoked potentials (SEP) were measured 75 min after injection of TRH or serum saline. SEP latencies were 28.1 0.6, 29.4 0.8, 27.8 1.1 ms, in normal, diabetic and diabetic TRH-treated groups, and NCV values were 28.1 0.8, 23.8 0.4, and 27.9 0.7 m/s respectively. NCV was significantly reduced in the diabetic group compared to normals (P 0.05), but then improved by TRH treatment (P 0.05). Our findings suggest that TRH has an acute effect on peripheral neuropathy in experimental streptozotocin diabetes in the rat. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Diabetic neuropathy; Somatosensory evoked potentials; Nerve conduction velocity; Streptozotocin; Rat 1. Introduction Diabetic neuropathy is a progressive disorder that causes functional and structural alterations of the peripheral, autonomic and central nervous systems. There is no effective medical therapy * Corresponding author. Tel.: +90-312-3044766; fax: +90- 312-3234923. E-mail address: oyildiz@neuron.ato.org.tr (O. Yildiz) 0168-8227/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII:S0168-8227(99)00028-5