Having battled many problems involving tension in my upper body, let me take a crack at this. The problem is a little more complex than just worrying about the throat. The way to change the way the throat feels, is to change the way you supply air to the trumpet. If you are blowing "hot" air (I'll explain), the throat/mouth/tongue must be in the most open position possible. Blowing "hot" air or blowing slow air is accomplished by imagining your hands are cold and how you would blow on them. The mouth would be very open, the breath would come out still warmed by the body and not moving so fast that it will loose all its heat before it gets to your hands. We can also talk of vowel quality - form your mouth for the word "Ho" as if to say it with as deep/dark and resonant a voice as possible. What I have been working on recently involves this as a crucial part of the process. Then, I must place tongue between my teeth and lips before setting the mouthpiece to help keep this distance between them. The lips form the embouchure by coming together from the inside (a pucker) and the buzz is constantly moving farther and farther back. The end result is a much more resonant sound. The problem is my body wants to over work to play and I find myself constantly having to consciously NOT over blow the embouchure. You see, the lips must resist the air stream. The harder you blow, the more they have to resist (tighten) - which will cause you to blow harder and there is the unnecessary tension. If the tongue comes up, this increases the resistance to the air stream before it gets to the lips, and also creates a cascading problem situation where the air is not plentiful at the point of buzz but it is fast, so the lips have to over tighten to control the pitch.
One famous teacher talks about learning to control the air stream. This new way of thinking is more like controlling the air column, using the lips as the control mechanism. Mr. Jacobs said the first point of resistance to the air is at the lips. I get the feeling that the mouthpiece is going to push the lips between my teeth - this also has the increased benefit of making you reduce mouthpiece pressure (which frees the lips to vibrate and reduces the amount of air pressure needed to counteract the tension created by the mouthpiece pressure). I am also applying the wisdom of Herbert L Clarke and working on subtones and extreme soft playing with this approach. There really is a reason behind the instructions supplied with the Clarke Technical Studies.
As I learn to trust this new approach and relax, I can play much louder and higher with far less effort and with a more resonant and consistent sound. My low registers are opening up for the first time in my life. The main problem is blowing slowly enough to play softly - it is too easy to play loud like this when you are used to over blowing for the same result.
Hope this helps...