Psychopharmacological evidences for the involvement of muscarinic and nicotinic cholinergic receptors on sweet substance-induced analgesia in Rattus norvegicus

• Published in: Neuroscience letters 2001-06, Vol.305 (2), p.115-118
• Main Authors: Irusta, A.E.C, Savoldi, M, Kishi, R, Resende, G.C.C, Freitas, R.L, Carvalho, A.D, Coimbra, N.C
• Format: Article
• Language: English
• Subjects: Acetylcholine; Acetylcholine - physiology; Analgesia; Analgesics - pharmacology; Animals; Atropine - pharmacology; Biological and medical sciences; Drug Administration Schedule; Fundamental and applied biological sciences. Psychology; Male; Mecamylamine - pharmacology; Muscarinic receptors; Nicotinic receptors; Nociceptors - drug effects; Pain Measurement; Pain Threshold - drug effects; Psychopharmacology - methods; Rats; Rats, Wistar; Rattus norvegicus; Reaction Time - physiology; Receptors, Muscarinic - physiology; Receptors, Nicotinic - physiology; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Sucrose - administration & dosage; Sucrose - pharmacology; Sweet substance-induced analgesia; Synaptic Transmission - physiology; Tail-flick test; Taste - physiology; Vertebrates: nervous system and sense organs
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/S0304-3940(01)01824-9

In order to investigate the effects of sweet substance intake on pain modulation, male albino Wistar rats weighing 180–200 g received either tap water or sucrose solutions (250 g/l) for 14 days as their only source of liquid. Each rat consumed an average of 15.6 g sucrose/day. Their tail withdrawal latencies in the tail-flick test (probably a spinal reflex) were measured immediately before and after this treatment. An analgesia index was calculated from the withdrawal latencies before and after treatment. The index (mean±SEM, N=8) for the groups receiving sucrose solution plus saline (NaCl; 0.9%) for 14 days was 0.70±0.01. Atropine (1 and 2 mg/kg)-treated rats ( N=8) after intake of sucrose exhibited an analgesia index of 0.39±0.09 and 0.39±0.08, respectively, while mecamylamine (1 and 2 mg/kg)-treated rats ( N=10) after intake of sucrose had an index of −0.02±0.07 and 0.03±0.07, respectively. These results indicate that the effect of sucrose intake on nociceptive thresholds is controlled by neurotransmission of acetylcholine and depends on the nicotinic cholinergic receptors for its major analgesic effect, although muscarinic receptors were also involved in this antinociceptive process.