ADH Release from Cut Pituitary Stalk and Intact Pituitary Gland during Hippocampal Stimulation of Various Frequencies in Rats

Abstract

Release of antidiuretic substance (vasopressin) from the central end of the cut pituitary stalk and the urine flow rate were estimated during electrical stimulation of the CA₁ field of the left hippocampus in rats. Frequencies of 4, 12, or 36 c/sec were used for hippocampal stimulation during the collection of the antidiuretic substance released from the cut infundibular axons, and frequences of 4 or 36 c/sec were used for hippocampal stimulation during urine flow determination. In all experiments, the current and voltage were adjusted to obtain approximately the same energy per train of pulses (2,160 nanowatt seconds). The antidiuretic activity of the fluid washing the cut pituitary stalk decreased during 4 c/sec hippocampal stimulation, showed no significant change during 12 c/sec stimulation, and increased considerably during 36 c/sec stimulation. The rate of urine flow did not alter during hippocampal stimulation at 4 c/sec, but decreased markedly during 36 c/sec stimulation. It is assumed that the hippocampus is able to trigger an increase or decrease in the rate of axoplasmic flow of antidiuretic substance and in the release of antidiuretic hormone from the pituitary gland. The frequency of hippocampal stimulation determines the response when the energy per train of electrical pulses remains constant.

ADH Release from Cut Pituitary Stalk and Intact Pituitary Gland During Amygdala Stimulation at Various Frequencies in Rats

“…After an initial decrease the urine flow returned to the control value during 50-60 min of stimulation. This effect was also obtained in response to dorsal hippocampal stimulation [Tomas et al, 1973] and it is likely that it was caused by some habituation to the trains of electrical pulses of the same energy.…”

“…The present investigation was to study whether a similar relationship exists between the nucleus medialis of amygdala and the hypothalamus as has been previously shown to exist between the CAt field of hippocampus and the hypothalamus [Tomas et al, 1973]. Fig.…”

“…The methods for preparing the animals for the collection of ADS from the cut pituitary stalk and deep brain structure stimulation, and preparing animals with intact pituitary glands for urine outflow measurement and deep brain structure stimulation have been fully described elsewhere [Tomas et al, 1973].…”

“…Electrical pulses of 4 or 36 cycles per second (cps) were used and in both cases the same energy (about 2.160 nanowatt seconds) per 1.5-sec train of electrical pulses remained constant. Antidiuretic substance release from the hypothalamic end of the cut pituitary stalk and from the intact pituitary gland increased during the 36-cps electrical stimulation of amygdala medial nucleus, however the 4-cps electrical stimulation of this structure did not produce any changes in these processes.The results obtained indicate that the medial nucleus of amygdala is able to change the function of the hypothalamo-hypophysial system and can be motivated with high frequency stimulating pulses.Direct electrical stimulation of the region of nucleus supraopticus of the hypothalamus induced diuresis inhibition in chronically waking animals regardless of the frequency of pulses applied [Traczyk and J a k u bo w sk a , 1966], The stimulation of dorsal hippocampus, the area where pathways to the hypothalamus originate, produced different results depending on the frequency of pulses applied [Tomas et al, 1973]. High frequency of stimu lating pulses inhibited diuresis and increased ADS release from the cut 1 Conducted under contract no.…”