Intrinsic connections within the pedunculopontine tegmental nucleus are critical to the elaboration of post-ictal antinociception

• Published in: Synapse (New York, N.Y.) N.Y.), 2014-08, Vol.68 (8), p.369-377
• Main Authors: Mazzei-Silva, Elaine Cristina, de Oliveira, Rithiele Cristina, Garcia, Tayllon Dos Anjos, Falconi-Sobrinho, Luiz Luciano, Almada, Rafael Carvalho, Coimbra, Norberto Cysne
• Format: Article
• Language: English
• Subjects: Animals; Catheters, Indwelling; Central Nervous System Agents - pharmacology; Cobalt - pharmacology; Male; Nociception - drug effects; Nociception - physiology; Pain Measurement; Pain Perception - drug effects; Pain Perception - physiology; Pain Threshold - drug effects; Pain Threshold - physiology; pedunculopontine tegmental nucleus; Pedunculopontine Tegmental Nucleus - drug effects; Pedunculopontine Tegmental Nucleus - physiopathology; Pentylenetetrazole; post-ictal antinociception; Rats, Wistar; Reticular Formation - drug effects; Reticular Formation - physiopathology; Seizures - physiopathology; Synapses - drug effects; Synapses - physiology; synaptic transitory blockade; Tail - physiopathology; Time Factors; tonic-clonic seizures
• ISSN: 0887-4476; 1098-2396
• DOI: 10.1002/syn.21749

ABSTRACT This study investigated the intrinsic connections of a key‐structure of the endogenous pain inhibitory system, the pedunculopontine tegmental nucleus (PPTN), in post‐ictal antinociceptive process through synaptic inactivation of the PPTN with cobalt chloride. Male Wistar rats (n = 6 or 7 per group), weighing 250–280 g, had the tail‐flick baseline recorded and were submitted to a stereotaxic surgery for the introduction of a guide‐cannula aiming at the PPTN. After 5 days of postoperative recovery, cobalt chloride (1 mM/0.2 µL) or physiological saline (0.2 µL) were microinjected into the PPTN and after 5 min, the tail‐withdrawal latency was measured again at 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 min after seizures evoked by intraperitoneal injection of pentylenetetrazole (64 mg/kg). The synaptic inactivation of PPTN decreased the post‐ictal antinociceptive phenomenon, suggesting the involvement of PPTN intrinsic connections in the modulation of pain, during tonic‐clonic seizures. These results showed that the PPTN may be crucially involved in the neural network that organizes the post‐ictal analgesia. Synapse 68:369–377, 2014. © 2014 Wiley Periodicals, Inc. The transitory synaptic blockade within the pedunculopontine tegmental nucleus decreased post‐ictal antinociception caused by tonic and tonic‐clonic seizures pharmacologically induced by peripheral administration of pentylenetetrazol.