Post-ictal analgesia: involvement of opioid, serotoninergic and cholinergic mechanisms

• Published in: Brain research Vol. 888; no. 2; pp. 314 - 320
• Main Authors: Coimbra, N.C, Castro-Souza, C, Segato, E.N, Nora, J.E.P, Herrero, C.F.P.S, Tedeschi-Filho, W, Garcia-Cairasco, N
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 12-01-2001; Amsterdam Elsevier; New York, NY
• Subjects: 5-HT 2 receptor; Analgesia; Animals; Atropine - administration & dosage; Biological and medical sciences; Convulsants; Disease Models, Animal; Endogenous opioid; GABA A receptor; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Injections, Intraperitoneal; Ketanserin - administration & dosage; Medical sciences; Methysergide - administration & dosage; Motor Activity - drug effects; Muscarinic Antagonists - administration & dosage; Muscarinic receptor; Naloxone - administration & dosage; Narcotic Antagonists - administration & dosage; Nervous system (semeiology, syndromes); Neurology; Pain Measurement - drug effects; Pentylenetetrazol; Pentylenetetrazole; Post-ictal analgesia; Rats; Rats, Wistar; Reaction Time - drug effects; Reflex - drug effects; Seizures - chemically induced; Seizures - metabolism; Seizures - physiopathology; Serotonin Antagonists - administration & dosage; Tail-flick test; GABA A receptor; Tail-flick test; Neurotransmitters, modulators, transporters and receptors; Pentylenetetrazol; Endogenous opioid; Muscarinic receptor; Post-ictal analgesia; 5-HT 2 receptor; Nervous system diseases; Pentetrazol; Rat; Epilepsy; Opioid receptor; Rodentia; 5-HT2 Serotonine receptor; Cerebral disorder; Analgesia; Cholinergic receptor; Vertebrata; Experimental disease; Mammalia; Tail flick test; Animal; Central nervous system disease; Gabaergic receptor A
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(00)03103-6

The neural mechanisms involved in post-ictal analgesia remain to be elucidated. Pentylenetetrazol (PTZ) is used experimentally to induce seizure in animal subjects. This non-competitive antagonist blocks GABA-mediated Cl
− flux. The aim of this work is to study the neurochemical basis of the antinociception induced by convulsions elicited by peripheral administration of PTZ (64 mg/kg). The analgesia was measured by the tail-flick test, in eight rats per group. Convulsions were followed by significant increase in the tail-flick latencies (TFL), at least for 30 min of the post-ictal period. Peripheral administration of naloxone (5 mg/kg and 10 mg/kg), atropine (1 mg/kg and 5 mg/kg), methysergide (1 mg/kg and 5 mg/kg) and ketanserine (1 mg/kg and 2 mg/kg) caused a significant decrease in the TFL in seizing animals, as compared to controls. However, while naloxone antagonized analgesia 15 and 25 min post convulsions, the other drugs caused a blockade of the post-ictal analgesia in a relatively greater period of time. These results indicate that endogenous opioids, serotonin and acetylcholine may be involved in post-ictal analgesia.