Fine structural survey of the mammillotegmental projections to the dorsal tegmental nucleus of gudden in the rat

s49

MEMBRANE CHARACTERISTICS OF SEPTAL THERMOSENSITIVE NEURONS. TOSHIHIRO NAKASHIMA', TOSHIKAZU School

840-01 and 2Dept. Physiol.,

we investigated neurons

in rat

the

septal

KIYOHARA', AND TETSURO

membrane characteristics

tissue

HOR12, ‘Dept.

Fat. Med., Kyushu University,

slices

at different

of

thermosensitive

temperatures

Physiol..

Saga Medical

Fukuoka 812, Japan. and thermally

by intracellular

insensitive

recording.

The input

resistance was measured by application of inward or outward current pulses during changes in slice

temperature

between 33 and 41 “C. The resting

and showed an input rate

to

a rise

resistance

in slice

of 20-50 M

temperature,

Q

showed

membrane potential

Warm-sensitive

of the neurons was 50-80 mV

neurons,

a large decrease

which increased

the firing

in the input resistance and

depolarization at higher temperatures. Thermally insensitive neurons did not show any changes in the membrane

resistance or resting potential during changes

in temperature. Cold-sensitive

neurons showed a decrease in membrane resistance with ahyperpolarization at higher temperature. The resting membrane potential of cold-sensitive neurons was depolarized and membrane resistance was not changed by perfusing with Na+free solution.

FINE STRUCTURAL

SURVEY

OF THE

MAMMILLOTEGMENTAL

PROJECTIONS TO

THE

DORSAL

TEGMENTAL NUCLEUS OF FUDDEN IN THE RAT. TETSU HAYAKAWA, AND KATUYA ZYO, Department Anatomv,

Hvono College of Medicine, Mukogawa,

The dorsal tegmental neuropil

of TD contains

pleomorphic

nucleus of Gudden (TD) is composed of a pars ventralis (TDV) and a pars dorsalis (TDD). The three classes

of axodendritic

Injections

labeled

of WGA-

terminals

synaptic

labeled terminals intermediate

terminals;

these are terminals

HRP into the lateral mammillary

visualized

containing

round,

flat, and

contacts.

often contact retrogradely

synaptic contacts, and 19% contain pleomorphic

More than 50% of labeled terminals

contain round vesicles with asymmetric

dendrites.

nucleus permits fine structural

recognition

of

with TMB within both the TDV and TDD. In the TDV, 81% of labeled

terminals contain round synaptic vesicles with asymmetric symmetric

of

Hvogo 663, JAPAN.

synaptic vesicles. These three types make up 44%, 5%, and 51% of the TDV, and 62%, l%, and 37% of the

TDD, respectively. anterogradely

Nishinomiva,

There are no labeled terminals

contact intermediate

synaptic contacts.

dendrites.

vesicles with

In the TDD, 90% of

One half of the labeled terminals

with flat vesicles in the TD. Anterogradely

labeled dendrites in the TDV, but there are no reciprocal

connections

contacts

labeled axon terminals

in the TDD.

16. Invertebrates RESPONSE CHARACTERISTICS OF MECHANORECEPTORS AND THEIR DISTRIBUTIONS IN THE SHIKO CHICHIBU, ATSUSHI CHIBA, HAMAGUCHI", MASAAKI KOSAKA?', CRAYFISH. Department of Physiolology, TATSUYA TOKUNO*, and TOSHIHARU ASAI* Kinki School ofedicine, Osakema, Osaka 589, a University -Mechanosensory hairs on the crayfish, Procambarus clarkii, show a number of different shapes according to their functions. Each sensory hair is innervated by one pair of sensory neurons at its base. The mobility of the hair is mainly and the structure is different due to due to the flexibility at the socket, the functions either for touch or for water current detections. The nobility of the hair is decreased from the head toward the tail in general. This relation is also correlated to the detection ability of the innervating neurons for transient stimuli. the highest impulse frequency to mechanical stimuli was divided When the ratio the the mean resting discharge frequency, indicated responsive by strength of the sensory neuron. The ratios for the A, V and D units on the endopodium of the first antenna were roughly 70, 10 and 4, respectively. Comparison of the transiently responding units on the endopodium, first showed ratios of 70, 22, 8 and 5, dactylopodite, cephalothorax and telson The transient properties of mechanical stimuli would be detected respectively. the receptors on the cranial parts, while the strong static properties are by detected by those on the caudal parts of the body.