Effect of Atropine Sulfate on the Sleep-Related EEG Spike Activity of the Tortoise, <i>Geochelone carbonaria</i>

Abstract

Preliminary pharmacological studieshave suggested that the most prominent electroencephalographic events of mammalian slow-wave sleep (SWS) – slow waves and spindles – and the most prominent electroencephalographic feature of reptilian sleep – a high voltage (up to 200 µV), fast (up to 150 msec) spike – may respond similarly to centrally acting drugs. To further evaluate the correspondence between mammalian SWS and reptilian spikes, atropine sulfate, a centrally acting cholinergic blocking agent which increases slow waves in mammals, was administered to ten tortoises, Geochelone carbonaria, chronically implanted for electroencephalogram and electrocardiogram recordings. Five of these animals also received atropine methyl nitrate, a peripherally acting cholinergic blocker. Both drugs were administered in a dose of 1.0–1.5 mg/kg. Baseline recordings and recordings after saline injection were made for each animal. Recording sessions under each condition were 48 h long and were counterbalanced with respect to order.A dramatic increase in spike activity was seen within 4–12 h after atropine sulfate administration relative to saline injection (p<0.02). By hours 37–48 postinjection there was no significant statistical difference in spike rates between saline and atropine sulfate conditions. Atropine methyl nitrate had no statistically significant effect upon spike rates for the first 12 h postinjection. Baseline rates of spiking and spike rates after saline injection were not significantly different. A dissociation between electroencephalographic activity and behavior after atropine sulfate administration was not seen.These results support the analogy of mammalian SWS and reptilian spikes. Both are increased after administration of atropine sulfate, and both are centrally mediated phenomena. Whether reptilian spikes and mammalian SWS have a similar functional significance, however, cannot be determined without further study.

Partial homologies between sleep states in lizards, mammals, and birds suggest a complex evolution of sleep states in amniotes

“…In reptiles, pharmacological experiments have also been conducted. In the 70s, injections of atropine sulfate, amphetamine, nembutal, alpha-methyl-tyrosine, and parachlorophenylalanine, drugs known to modify the quantity of ventral hippocampal sharp waves in the cat, were shown to induce the same effects on turtle sharp waves ( Geochelone carbonaria ) [ 53 , 54 ]. This let the authors suggest that reptilian HShWs could be similar to mammalian sharp waves.…”

Developmental appearance and disappearance of cortical events and oscillations in infant rats

“…However, several decades ago, researchers discovered a “high-voltage, fast spike potential” within the reptilian pallium that predominantly occurs during periods of behaviorally defined sleep. These events were mono-, bi-, or polyphasic with a mean duration of 150 ms and an amplitude of 200–300 μV (Hartse, 1994; Hartse and Rechtschaffen, 1974). …”