The Reactivity of Wistar Rats Highly Selected for Good and Bad Learning, Observed in Various Physiological and Pharmacological Test Models. 1st. Communication

Abstract

Preliminary investigations on selected rats, bred from Wistar WU/Ivanovas since 1966, presented the following results:

• 1. No differences could be detected between GL and BL as far as the pharmacological action on peripheral organs and receptors are concerned, viz. inflammation by means of Freund’s adjuvant, sensitivity to nor-adrenalin of the vascular system and sensitivity to carbachol and acetylcholine of cholinergic receptors in the gastrointestinal tract.

• 2. Without detectable differences in GL and BL were the effects of centrally acting substances such as myotonolytic tranquilizers, cataleptics, convulsants and narcotics.

• 3. Equally undifferentiated were pain sensitivity and exploration behaviour in both strains. These factors, therefore, do not come into consideration as causal agents of the differences in learning capacity of GL and BL.

• 4. Contrary to this, GL generally appeared to be slightly more sensitive to central stimulants and the sympathomimetic amphetamine, BL, however, distinctly more sensitive to the cholinergic tremorine(induced tremor). This is in accordance with the concepts of KHAVARI (1971) and LEITH and BARRETT (1971). KHAVARI assumes “implication of a dichotomous CNS adrenergic-cholinergic neurotransmitter mechanism in the control of learned behaviour”. LEITH and BARRETT conclude that “differences between strains in the avoidance performance are, at least partially, related to variations in the relative activity of the cholinergic and adrenergic systems”. Our own observations, however, demonstrated here a marked overlapping with the sex differences.

• 5. Distinct sex differences often exist.

• 5.1. The female animals are more sensitive to the chemical pain stimulant phenylbenzoquinone and explore slightly more frequently than the males. This could explain, at least in part, a difference in learning ability between the two sexes of the same strain.

• 5.2. In contradistinction to this, the females are more insensitive to two centrally acting muscle relaxants (at a higher level of the basic tonus), two narcotics and two cataleptics. A prominent sex difference was brought about by the cataleptic tetrabenazine. This sex difference could also be demonstrated in the control animals of two unselected strains. No sex differences in the narcotic action could be observed after hexobarbital administration. It is envisaged to extend our studies with GL and BL.

  The last contribution contains a literature survey as well as an extensive discussion on the results of our own investigations.