"The experimental procedure was based on published techniques (Reinhardt, 1971). The gas bags were prepared before each exposure session and the target concentration established before any dogs were

exposed. Once the level was established, the dog was placed in the sling and fitted with the mask. At this stage the dog was breathing room air. Adrenaline solutions were prepared immediately prior to each exposure session from a stock solution (Adrenaline 1: 1000, Phoenix Pharmaceuticals Ltd., Gloucester, England) and sterile pyrogen- free water (Formulation Department). Injections were given at a rate of 0.1 mi/second.

Appropriate dilutions were used such that the volume of adrenaline solution used was consistently 0.1 ml/kg bodyweight.

The ECG was established (as described previously) and the timing commenced as shown below:

Time(minutes): Event

0 Start ECG recording

2 First adrenaline(D1) challenge administered

7 Gas reservoir connected to air supply line

12 Second adrenaline (D2) challenge administered

17 Gas reservoir disconnected

Stop ECG recording

EXPERIMENTAL DESIGN

The study was performed in 2 stages:

STAGE 1

In this stage an individual response to adrenaline alone was selected for each of the 9 dogs using a range of adrenaline doses. The response to administration of adrenaline is dependent on the dose given and the responsiveness of each individual dog. Typically the response consists of a transient increase in heart rate followed by a reflex slowing of the heart rate and an increase in the height of the T-wave, occasionally multiple unifocal ventricular tachycardia may occur. The purpose of Stage 1 of the study was to establish an adrenaline dose at which there was a clear but minimal effect on the ECG ideally with a few ectopic beats. The actual dose level at which the various responses occurred was dependent on the individual dog. A suitable adrenaline dose had been selected for each of the previously used dogs. Each dog was re- tested at the established adrenaline dose and where necessary a new dose was established. If no ectopic beats were observed for a particular dog the adrenaline dose was increased until a response was observed. Conversely, if too many ectopic beats were observed the dog was allowed to recover and the adrenaline dose was reduced until an acceptable dose was found. If necessary, the Study Director and monitoring toxicologist applied a judgement in the selection of an appropriate adrenaline dose in the best interests of the dog and the study integrity. When an appropriate dose had been selected, that dose was used for the exposures in Stage 2. Each of the dogs allocated to the study was tested as indicated in the EXPERIMENTAL PROCEDURE, except that no test gas was used and the dogs received air only for the 17 minutes. On completion of Stage 1, 6 of the dogs were allocated for use in Stage 2. Details of the results of Stage 1 of the study and the rationale for the selection of the dogs for Stage 2 of the study are given in the RESULTS section of the report.

STAGE 2

Each of the dogs selected for Stage 2 was exposed to the test gas according to the EXPERIMENTAL

PROCEDURE. The dogs were exposed according to the following schedule:

Exp Session: Target T-7479 concentration (% v/v in air) 1 Air only

2 1.0

3 2.0

4 5.0

5 10.0

6 15.0

At least one calendar day was allowed between each exposure session to allow the dogs to recover."

Male Beagle dogs