The effects of gaba and biogenic amines behavior and brain electrical activity in chicks

Evidence for both photopic and scotopic characteristics in the c-wave of chicken and frog ERG

The electroretinographic c-wave was studied in two species with duplex retinas, the frog (rod-dominant) and the chicken (highly cone-dominant). In both species a cone driven c-wave was recorded in addition to the classical rod-driven c-wave. An attempt was made to specify the differential characteristics with respect to time-course, time integration, adaptational changes and spectral sensitivity of cone-driven vs rod-driven c-waves. These data confirm the generality of the c-wave generation by both rod and cone systems.

Enhancement of 5-hydroxytryptamine-induced behavioral effects following chronic administration of antidepressant drugs

It has been shown recently that chronic administration of tricyclic antidepressant drugs results in enhanced responsiveness of neurones to iontophoretically applied 5-hydroxytryptamine (5-HT) in rat forebrain regions. The present investigation tested whether this efect is accompanied by an enhancement of behavioral effects of the amine. Behavioral signs of sleep in young chicks following systemic administration of 5-HT were used as an index of the acion of the amine at central receptor sites. Imipramine, desipramine, amitryptiline, pizotifen, and mianserin given 30 min before 5-HT all reduced the duration of 5-HT-induced behavioral depression. However, 6-8 day pretreatment with the same drugs resulted in an increased duration of the 5-HT-induced depression. The results suggest that the antidepressant drugs can block 5-HT receptors in the central nervous system (CNS) and that chronic blockade resulting from repeated administration of the drugs results in an increase in number or sensitivity of 5-HT receptors.

Enhancement of picrotoxin convulsions in chicks and mice by the prior intraperitoneal injection of hypertonic GABA or mannitol

Effects of i.p. injection of hypertonic solutions of GABA and mannitol on convulsant activity and latency to reduced or enhanced depending on whether picrotoxin was given i.p. or given i.v. or s.c. The principal cause of these changes appeared to be altered rates of absorption of picrotoxin. There was no evidence that cerebral dehydration afforded protection against picrotoxin.

Distribution of monoamine-containing terminals and fibers in the central nervous system of the chicken

In the mesencephalon of the chicken, the two large groups of CA terminals and fibers appeared to correspond to the dorsal and ventral bundles of the CA containing fibers in the rat. These ran rostrally in the medial forebrain bundle and appeared to terminate within the thalamus, hypothalamus, preoptic region and corpus striatum. 5-HT containing terminals and fibers also were observed in the mesencephalon and appeared to run rostrally in the medial part of the medial forebrain bundle. In comparison with the CA terminals, however, 5-HT terminals were for the greater part, difficult to observe in many areas of the brain. Based on the observation concerning postnatal ontogeny of monoamine-containing neurons, the chicken brain appears to acquire behavioral and functional maturity at an earlier stage after birth than does that of the rat. Effect of reserpine, nialnmide, L-Dopa and 5-HTP on the monoamine-containing terminals and fibers are briefly discussed.

Pharmacological properties of amino-oxyacetic acid in the chicken

1. The effects of amino-oxyacetic acid (AOAA) on the central nervous system and on skeletal muscle have been examined in the chicken.2. AOAA had both anticonvulsant and convulsant effects, depending on the dose, as in other species.3. The convulsant effect, accompanied by EEG spiking, decreased rapidly with increase in age of young chicks.4. The convulsant effect was exerted primarily through supraspinal centres.5. Of control depressants tested, only troxidone and small doses of AOAA afforded significant protection against AOAA seizures.