The effects of nicotine on locomotor activity in non‐tolerant and tolerant rats

The effects of nicotine on locomotor activity in non‐tolerant and tolerant rats 1 Rats were tested for locomotor activity in photocell cages, for 80 min starting immediately after subcutaneous injection of (−)‐nicotine bitartrate or 0.9%w/v NaCl solution (saline). In non‐tolerant subjects, nicotine (0.1 to 0.4 mg/kg base) depressed activity and induced ataxia in the first 20 min, but increased activity later in the session; these actions were dose‐dependent. 2 Tolerance was studied by comparing rats given nicotine (0.4 mg/kg s.c.) every day with control rats given saline instead. Each week, every subject was tested once with nicotine (0.4 mg/kg) and once with saline. With daily or even weekly injections of nicotine, the initial depressant action of the drug was replaced by a dose‐dependent stimulant action which occurred throughout the session. In these tolerant animals, little ataxia was seen except when a larger dose of 0.8 mg/kg was given. Tolerance to the depressant action of nicotine persisted for at least 3 weeks. 3 In non‐tolerant subjects, mecamylamine (0.5, 1.0 mg/kg s.c.) prevented the initial depressant action of nicotine (0.4 mg/kg). In tolerant rats, the locomotor stimulant action of nicotine (0.4 mg/kg) was prevented by mecamylamine (0.1, 0.32, 1.0 mg/kg s.c.) in a dose‐related way; the quaternary ganglion blocker, hexamethonium (0.2, 1.0, 5.0 mg/kg s.c.) had little or no such effect. Neither mecamylamine nor hexamethonium altered activity when given alone. 4 It is suggested that a few treatments with nicotine can unmask a stimulant action of the drug, probably of central origin, which possibly reflects a stimulation of nicotine receptors. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png British Journal of Pharmacology Wiley

The effects of nicotine on locomotor activity in non‐tolerant and tolerant rats

British Journal of Pharmacology, Volume 78 (2) – Feb 1, 1983

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Publisher
Wiley
Copyright
1983 British Pharmacological Society
ISSN
0007-1188
eISSN
1476-5381
D.O.I.
10.1111/j.1476-5381.1983.tb09398.x
Publisher site
See Article on Publisher Site

Abstract

1 Rats were tested for locomotor activity in photocell cages, for 80 min starting immediately after subcutaneous injection of (−)‐nicotine bitartrate or 0.9%w/v NaCl solution (saline). In non‐tolerant subjects, nicotine (0.1 to 0.4 mg/kg base) depressed activity and induced ataxia in the first 20 min, but increased activity later in the session; these actions were dose‐dependent. 2 Tolerance was studied by comparing rats given nicotine (0.4 mg/kg s.c.) every day with control rats given saline instead. Each week, every subject was tested once with nicotine (0.4 mg/kg) and once with saline. With daily or even weekly injections of nicotine, the initial depressant action of the drug was replaced by a dose‐dependent stimulant action which occurred throughout the session. In these tolerant animals, little ataxia was seen except when a larger dose of 0.8 mg/kg was given. Tolerance to the depressant action of nicotine persisted for at least 3 weeks. 3 In non‐tolerant subjects, mecamylamine (0.5, 1.0 mg/kg s.c.) prevented the initial depressant action of nicotine (0.4 mg/kg). In tolerant rats, the locomotor stimulant action of nicotine (0.4 mg/kg) was prevented by mecamylamine (0.1, 0.32, 1.0 mg/kg s.c.) in a dose‐related way; the quaternary ganglion blocker, hexamethonium (0.2, 1.0, 5.0 mg/kg s.c.) had little or no such effect. Neither mecamylamine nor hexamethonium altered activity when given alone. 4 It is suggested that a few treatments with nicotine can unmask a stimulant action of the drug, probably of central origin, which possibly reflects a stimulation of nicotine receptors.

Journal

British Journal of PharmacologyWiley

Published: Feb 1, 1983

References

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